Haptic Devices: Wearability-Based Taxonomy and Literature Review

Abstract

In the last decade, several new haptic devices have been developed, contributing to the definition of more realistic virtual environments. An overview on this topic requires a description of the various technologies employed in building such devices, and of their application domains. This survey describes the current technology underlying haptic devices, based on the concept of “wearability level”. More than 90 devices, newly developed and described in scientific papers published in the period 2010-2021, are reviewed, which provide either haptic illusions or novel haptic feedback for teleoperation, entertainment, training, education, guidance and notification. As a result, the analyzed systems are divided into grounded, hand-held and wearable devices; the latter are further split into exoskeletons and gloves, finger-worn devices, and arm-worn devices. For the systems in each of these categories, descriptions and tables are provided that analyze their structure, including device mass and employed actuators, their applications, and other characteristics such as type of haptic feedback and tactile illusions. The paper also provides an overview of devices worn in parts of the human body other than arms and hands, and precisely haptic vests, jackets and belts, and haptic devices for head, legs and feet. Based on this analysis, the survey also provides a discussion on research gaps and challenges, and potential future directions.

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Date of publication xxxx 00, 0000, date of current version xxxx 00, 0000.
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Haptic Devices: Wearability-Based
Taxonomy and Literature Review
ADILZHAN ADILKHANOV1(Student Member, IEEE), MATTEO RUBAGOTTI1(Senior Member,
IEEE), and ZHANAT KAPPASSOV1(Member, IEEE)
1Department of Robotics and Mechatronics, Nazarbayev University, 53 Kabanbay Batyr Ave, Z05H0P9 Nur-Sultan, Kazakhstan (e-mail: {adilzhan.adilkhanov;
matteo.rubagotti; zhkappassov}@nu.edu.kz)
Corresponding author: Zhanat Kappassov (e-mail: zhkappassov@nu.edu.kz).
This work was funded by Nazarbayev University under Collaborative Research Project no. 091019CRP2118 and Faculty Development
Competitive Research Grant no. 11022021FD2923, and by the Ministry of Education and Science of the Republic of Kazakhstan under
research grant AP09058050.
ABSTRACT In the last decade, several new haptic devices have been developed, contributing to the
definition of more realistic virtual environments. An overview on this topic requires a description of the
various technologies employed in building such devices, and of their application domains. This survey
describes the current technology underlying haptic devices, based on the concept of “wearability level”.
More than 90 devices, newly developed and described in scientific papers published in the period 2010-2021,
are reviewed, which provide either haptic illusions or novel haptic feedback for teleoperation, entertainment,
training, education, guidance and notification. As a result, the analyzed systems are divided into grounded,
hand-held and wearable devices; the latter are further split into exoskeletons and gloves, finger-worn devices,
and arm-worn devices. For the systems in each of these categories, descriptions and tables are provided
that analyze their structure, including device mass and employed actuators, their applications, and other
characteristics such as type of haptic feedback and tactile illusions. The paper also provides an overview of
devices worn in parts of the human body other than arms and hands, and precisely haptic vests, jackets and
belts, and haptic devices for head, legs and feet. Based on this analysis, the survey also provides a discussion
on research gaps and challenges, and potential future directions.
INDEX TERMS haptic devices, virtual reality interfaces, kinesthetic feedback, tactile feedback, haptic
illusions.
I. INTRODUCTION
THE word haptics refers to the capability to sense a
natural or synthetic mechanical environment through
touch [1]. The last decade has seen a dramatic increase of
haptic devices, driven by application domains such as haptic
robot teleoperation, virtual reality (VR) and augmented real-
ity (AR). However, there is still much work to be done before
people can fully interact with objects in a virtual environment
(VE). For example, realistic object manipulation, including
the perception of textures, shape, weight, softness and tem-
perature, is necessary for better immersion into the virtual
world. Thus, advancements in haptic devices are needed to
engage our sense of touch in addition to vision [2], which is
typically provided by head-mounted displays (HMDs).
Human haptic perception consists of both kinesthetic and
cutaneous (tactile) haptic feedback. Kinesthetic feedback
refers to the sense of position and motion of one’s body
state mediated by a variety of receptors located in the skin,
joints, skeletal muscles and tendons [1]. Cutaneous feedback
is instead related to the stimuli detected by low threshold
mechanoreceptors under the skin within the contact area [3].
Haptic devices are used to engage these types of feedback
and give users the feeling of touch, in some cases providing
haptic illusions. They receive information from a VE and act
on the user through tactile feedback; at the same time, they
send the sensed position and force data of the user to the VE.
Devices used to stimulate kinesthesia are typically
grounded, bulky, mechanically complex, expensive and have
a limited workspace. Traditionally, kinesthetic devices are
able to provide clear forces or torques to move the user’s
hand or resist motion [4]. They are widely used in industry
and medicine for teleoperation tasks and other tool-based
applications, e.g., using manipulator hands and dental drills
[5]. These devices typically provide the best approach for
high-quality interactions, but suffer from limitations in terms
of cost and portability.
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Adilkhanov et al.: Haptic Devices: Wearability-Based Taxonomy and Literature Review
To avoid the drawbacks of grounded kinesthetic devices,
the haptic feedback can be delivered through cutaneous
devices. Although cutaneous feedback can be in principle
provided for the whole body, it is mostly given through
fingertips, as these are usually employed for grasping and
manipulation, and are rich in mechanoreceptors [6]. It has
been shown that, to some extent, it is possible to compensate
for lack of kinesthesia with the modulated cutaneous force
technique, without significant performance degradation [7].
Cutaneous feedback can be displayed by mobile, lightweight,
compact devices that can be wearable and mounted on the
user’s body on wrist, palm and fingers.
Despite their complexity, not all kinesthetic devices are
grounded. Depending on their purpose, kinesthetic haptic
devices can be in the form of exoskeletons (grounded on
some part of the body).
A. EXISTING REVIEW PAPERS
Previous reviews in this field focused on haptic devices [1],
[4], [8], wearable haptic interfaces [9] including exoskeletons
and gloves [8], [10], [11], touch surfaces [12], and appli-
cations of haptic devices [5], [8], [13], [14], with nearly
all examined devices targeting parts of human arms and
hands. Some of these reviews [1], [4], [9], [12], provide
a background in the physiology of human sensory-motor
control.
The first survey on haptic interfaces and devices, and on
their applications, was written by Laycock and Day [8],
who also examined how haptic feedback was combined with
visual display devices (e.g., virtual reality walls and work-
benches), so as to improve the immersive experience.
The review paper by Hayward and coauthors [1] provided
a classification of haptics in human-computer interfaces.
The paper described examples of applications followed by
descriptions of human kinesthetic and tactile sensing, and
components of haptic interfaces, listing several devices in use
at that time.
Culbertson et al. [4] reviewed the technology behind cre-
ating artificial touch sensations focusing on design, control
and application of noninvasive haptic devices. Firstly, they
introduced a taxonomy of haptic systems, considering three
major categories: graspable, wearable and touchable. Further,
they discussed a variety of haptic feedback mechanisms
present in each device of the three categories.
The review by Pacchierotti et al. [9] analyzed a fraction
of haptic systems, considering only wearable haptics for
fingertip and hand, which provide cutaneous feedback. The
paper presented a taxonomy of haptic wearables, focused on
technological and design challenges, and reported future per-
spectives on the field. Wearable haptic systems were catego-
rized based on type of tactile stimuli, mechanical properties
and interested body part.
Unlike [9], Wang et al. [10] considered only glove-type
whole-hand wearables with kinesthetic feedback. The main
focus was on hardware technology and design challenges
at the levels of sensing, actuation, control, transmission and
structure. Firstly, the authors discussed anatomical aspects
that must be considered for the design of glove-type wear-
ables. Then, the existing research prototypes and commer-
cially available kinesthetic gloves were summarized. Force-
feedback gloves were categorized by actuation location into
digit-based, palm-based, dorsal-based and ground-based.
Perret and Vander Poorten [11] wrote another literature
review on haptic gloves. They briefly discussed the main
technical constraints appearing during the design process,
with a special focus on actuation technology. The classifica-
tion of haptic gloves differs from the one introduced in [10],
as they are divided into traditional gloves (made of flexible
fabric), thimbles, and exoskeletons. Finally, [11] analyzed
characteristics and performance of existing commercial de-
vices.
Bastogan et al. [12] reviewed another type of haptic
devices - surface haptics. The categorization in the paper
focused on the three most popular actuation methods: vibro-
tactile, electrostatic, and ultrasonic. The current technologies
for surface haptics displays were classified based on stim-
ulation direction and method. The modern state of the art
technologies in surface haptics were reviewed from three
perspectives: methods of generating tactile stimuli and the
physics behind them, human tactile perception, and tactile
rendering algorithms.
Other reviews on haptic devices focused on their appli-
cations. Rodriguez et al. [5] reviewed the applications of
haptic systems in VEs. The applications were divided into
three main categories: training, assistance, and entertainment.
Both kinesthetic and cutaneous feedback devices are consid-
ered for the review, in application fields such as education,
medicine and industry.
Shull et al. [14] wrote a review on haptic wearables for
clinical applications involving sensory impairments. The de-
vices were categorized into three groups depending on the
degree of disability - total impairment, partial impairment,
or rehabilitation. The review concluded that wearable haptic
devices facilitated the rehabilitation rate and improved func-
tionality of medical devices, including prostheses, in a variety
of clinical applications such as vestibular loss, osteoarthritis,
vision loss and hearing loss.
Talvas et al. [13] reviewed the state of the art on biman-
ual haptics - the field that studies haptic interaction with
either remote or virtual environments using both hands of
the same person. Currently available bimanual haptic de-
vices, software solutions and existing interaction techniques
were discussed with regard to specifications of the human
bimanual systems, such as the dominance of the hands, their
differences in perception and their interactions at a cognitive
level.
B. MOTIVATION AND CONTRIBUTION
The main motivation for writing this survey paper is the
need to provide a taxonomy for the considerable number of
recently developed haptic devices, which can allow readers to
capture the main trends that will determine the development
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Adilkhanov et al.: Haptic Devices: Wearability-Based Taxonomy and Literature Review
FIGURE 1: Two-level taxonomy of haptic devices based on wearability level (taxonomy level 1) and classification based on
further characteristics (taxonomy level 2).
FIGURE 2: Graphical examples of different types of haptic
devices classified by wearability level: (a) grounded haptic
device; (b) hand-held haptic device; (c) wearable haptic
device.
and design of haptic devices in the coming years. There-
fore, unlike [4], which classified haptic devices by design in
three major categories (graspable, wearable and touchable),
in this review we propose to classify them based on the
concept of wearability level. Indeed, the current trend in the
development of haptic devices consists in moving their base
closer to the place of stimulation, shifting from grounded
devices (which cannot be worn on parts of the user’s body)
to hand-held devices, and further towards fully wearable
devices. In other words, “only recently, more sophisticated
haptic systems have started to be designed with wearability
in mind.”, which “enables novel forms of communication,
cooperation, and integration between humans and machines"
[9]. As observed in the recent past for audio and video
electronics, the development of haptics is moving towards
devices with a higher wearability level to make them suit-
able in everyday life, the key design aspect being effective
integration with the human body without motion constraint.
Examples of commercially-available wearables that support
haptic feedback are smart watches such as AppleWatch (Ap-
ple, USA) and Gear (Samsung, South Korea).
To represent this trend in our taxonomy, in this review
we classify haptic systems by wearability level into three
categories (see Figs. 1 and 2):
•Grounded devices (not wearable), which are divided
into graspable and touchable systems.
•Hand-held devices (“partially” wearable), distinguished
based on type of actuation (direct or indirect) with
respect to the user’s limb.
•Wearable devices, further classified into exoskeletons
and gloves, finger-worn devices, and arm-worn devices.
This specific taxonomy based on wearability level is, to the
extent of our knowledge, a novel contribution. Furthermore,
for all categories, we describe the applications of the devices,
the types of employed actuators, and other characteristics
such as type of haptic feedback, haptic illusions, degrees
of freedom (DoFs), and physical properties such as mass.
For each category, we provide a table that summarizes the
most important features of more than 90 analyzed devices.
For key features regarding different types of illusions related
to object manipulation and perception (illusions of weight,
shape, size, stiffness, texture), we summarize the applicable
approaches. This review paper will be mainly focusing on
devices worn on human hands and arms, as these are by far
the most common. Indeed, hands constitute the main part of
the body with which humans physically interact with their
surroundings, also due to the large number of mechanore-
ceptors present in them. Nonetheless, there exist devices that
target different parts of the human body other than arms and
hands, in order to expand the range of applicability of haptics
to new scenarios. A brief overview of these devices will also
be provided in our paper.
C. SURVEY STRUCTURE
The remainder of the paper is organized as follows. The
method used to search and select the papers that describe
the analyzed haptic devices is provided in Section II. Section
III contains the descriptions of all the surveyed devices. In
particular, grounded and hand-held devices are reviewed in
Sections III-A and III-B, respectively. Wearable devices are
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Adilkhanov et al.: Haptic Devices: Wearability-Based Taxonomy and Literature Review
analyzed in separate subsections: exoskeletons in Section
III-C, finger-worn devices in Section III-D, and arm-worn
devices in Section III-E. A brief overview of devices for parts
of the human body other than arms and hands is provided
in Section III-F. A discussion of the applicability of the
reviewed devices in various contexts and of the different
types of tactile illusions is finally reported in Section IV.
II. METHOD
A. SEARCH AND SELECTION METHODOLOGY
The procedure followed for selecting the papers suitable for
this review was the following:
1) Suitable references were searched for by using rele-
vant keywords such as “haptic devices”, “haptic tech-
nology”, “tactile feedback”, “haptic interfaces” and
“wearable devices” in Google Scholar, ACM Digital
Library, IEEEXplore, SpringerLink and Web of Sci-
ence.
2) The papers that contained one or more of the given
keywords in the title and/or in the body of the paper
were extracted.
3) The papers that did not satisfy all of the following
requisites were removed:
•the approach described in the paper is original;
•the authors present a newly built device, or an
original modification of an existing device;
•the described haptic interface provides either hap-
tic illusions or novel haptic feedback for various
tasks such as teleoperation and navigation;
•the paper is published either in an international
journal or in an international conference in English
language from 2010 onward.
4) For the selected papers we analyzed (to find additional
devices) the references cited in them, together with the
papers that were citing them (via Google Scholar). For
the newly-found papers, the same selection procedure
detailed in steps 2) and 3) was followed.
As a result, more than 90 papers were found that satisfied the
above-mentioned requirements.
B. TAXONOMY DEFINITION
After determining the list of relevant papers, the follow-
ing step consisted of organizing them within the above-
mentioned taxonomy based on wearability level. More pre-
cisely, each paper was clustered into one of the following
categories and sub-categories:
•Grounded device, either
-- graspable, or
-- touchable.
•Hand-held device, either
-- with direct actuation, or
-- with indirect actuation.
•Exoskeleton, based on either
-- resistive force, or
-- locking mechanisms, or
-- pneumatic actuation.
•Finger-worn device, relying on either
-- a moving platform, or
-- a shearing belt, or
-- other solutions.
•Arm-worn device, based on either
-- vibrotactile feedback, or
-- skin stretch and compression feedback, or
-- thermal feedback.
The categories (e.g., grounded devices) were determined a-
priori based on our preliminary knowledge of the field; on
the other hand, the subcategories (e.g., graspable grounded
devices) were dynamically redefined as more papers were
classified. The haptic devices that were not designed to
be worn on arms or hands were instead classified into the
following three subcategories:
•vests, jackets and belts;
•devices for legs and feet;
•devices for head.
At the end of the search and categorization processes, we
proceeded generating the description of each paper, which
is reported in the following, in Section III. This review work
focuses on describing devices introduced in other scientific
papers (which are typically laboratory prototypes), for which
detailed descriptions and comparisons through tables are
provided. Nonetheless, several commercial devices are also
mentioned in the suitable subsections for the reader’s conve-
nience.
III. RESULTS
A. GROUNDED DEVICES
Grounded (also known as “tabletop”) haptic devices are those
that cannot be worn on a part of the user’s body, due to
their size and/or functional features, such as the presence
of air reservoirs or compressors. Therefore, the workspace
of such devices is limited. Grounded haptic systems can be
categorized into graspable and touchable devices (Figure 2a).
Since grounded devices are not as limited in terms of size and
weight as compared to hand-held and wearable devices, their
type of actuation can employ pneumatic actuation with its
bulky reservoirs and pumps, or magnetic actuation with its
platforms and large electric coils. A summary of the devices
described in the remainder of this section is provided in
Table 1.
1) Graspable Devices
Graspable haptic systems (Fig. 2a, left) are traditionally
kinesthetic devices, but some may provide cutaneous feed-
back (e.g., vibrations) through a held tool. Well-known com-
mercial examples of tabletop graspable devices are Touch
(3D Systems, USA - formerly Phantom from Sensable Tech-
nologies) and Omega (Force Dimension, Switzerland). These
types of haptic devices are very accurate and able to provide
a wide range of forces. The design of these devices is focused
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Adilkhanov et al.: Haptic Devices: Wearability-Based Taxonomy and Literature Review
TABLE 1: Grounded Haptic Devices
* - considered grounded due to water tanks; ** - speed of heating/cooling; *** - time for filling/emptying.
Device Type Purpose/Haptic Illusion Kinesthetic Feedback Cutaneous Feedback Actuators Max Force
[15] graspable teleoperation Force Dimension
Omega.3
normal/tangential
skin deformation
(x3) servomotors
(Futaba S3154 RC) 10 N
[16] graspable stiffness perception Phantom
Premium 1.5 skin stretch (x1) DC motor
(Portescap 16G88214E) 2 N
[17] graspable teleoperation N/A skin stretch (x6) layers of EAP
(3M VHB 4910 acrylic film) 1.6 N
[18] graspable 3D shapes force due to EMF N/A (x9) electromagnetic coils 2 N
[19] graspable 3D surface exploration force due to EMF N/A (x3) electromagnetic coils 0.959 N
[20] touchable textured surfaces N/A electrovibration (x1) capacitive-based touch
sensing panel (3M Microtouch) -
[21] touchable directional cues, friction N/A skin stretch (x2) Flexinol SMA wires 3 N
[22] touchable teleoperation N/A temperature feedback (x4) Peltier Elements **14.4°C/sec
**18.7°C/sec
[23] touchable surface relief N/A normal skin
deformation
(x16) DC motors
(Namiki SLC07-17) -
[24]
[25] touchable softness N/A normal/tangential
skin deformation
(x2) DC motors (Remax 2561:1
3W, Maxon Motros) 20 N
[26] touchable softness N/A vibrotactile (x1) VCA (Haptuator Mark 2) -
[27] touchable material roughness N/A vibrotactile (x1) VCA (X-1740, Aoyama
Special Steel Co., Japan) -
[28] touchable object slippage N/A skin stretch - -
[29] *wearable stroking, pulsing N/A compression and
temperature feedback
(x4) nylon-coated ripstop
fabric pouches + (x2) water pumps
(Bayite BYT-7A006)
***2.3 sec
***2.2 sec
on having several DoFs with small backlash in the joints, and
on using motors with high force and low friction and cogging.
Quek et al. [15] developed a haptic device that could be
attached at the end-effector of the above-mentioned Omega
device (Force Dimension). The novel device provides nor-
mal and tangential skin deformation feedback through the
movement of rubber tactors whose displacement is generated
by a delta parallel kinematic mechanism actuated by three
servomotors.
Afterwards, Quek et al. [16] presented another skin stretch
feedback device that used tactor movement - Skin Stretch
Stylus. The device consists of a vertical bar (with attached
skin stretch tactors) actuated by a DC motor through a cable
capstan mechanism, which slides on a linear guide carriage.
The Stylus is attached to a Phantom Premium device. While
the Phantom Premium provides force feedback, the Stylus
exerts skin stretch feedback during the interaction with a
virtual surface. This sensory augmentation causes a shift in
perceived stiffness proportional to the tactor-displacement
gain.
A similar device, presented by Han et al. in [17], was
aimed at assisting a surgeon during magnetic-resonance-
guided biopsy procedures - translating the forces sensed by
a robotized biopsy needle. The device provides localized
skin stretch to both the thumb and index fingertips of the
operator. The feedback is delivered through tactors driven by
electroactive polymer (EAP) actuators.
Adel et al. [18] presented a grounded electromagnetic-
based haptic interface. The device aims to render virtual
objects of different shapes with the use of an electromagnetic
field (EMF) generated by nine individually-controlled coils.
The EMF exerts magnetic forces on a permanent magnet
attached to the user’s fingertip. The fingertip position is
tracked by a Leap Motion optical hand-tracking module.
Another approach of providing contact-free, volumetric
haptic feedback via EMF was introduced in [19]. Unlike [18],
the device presented in [19] uses only three electromagnetic
coils placed orthogonally at the center of the base. The
magnetic field that exerts attractive and repulsive forces onto
a permanent magnet embedded into a hand-held stylus is
created by controlling the current flow. The device can be
effective in applications such as virtual terrain exploration
and rendering the sensation of stirring a viscous liquid. The
method of delivering haptic feedback through magnetism
(used in both [18] and [19]) also has limitations such as high
power consumption, strong cooling system requirement, and
a consequent limited continuous interaction.
2) Touchable Devices
Touchable haptic devices (Fig. 2a, right) are interactive dis-
plays that allow the user to tactilely interact with objects
displayed on the screen. These devices typically provide
pure cutaneous feedback through vibrotactile, electrostatic
or ultrasonic actuation methods. The idea is to use haptic
surfaces for those actions and applications that do not require
active movements or high-precision control, such as user
interface of different applications, online shopping, entertain-
ment, education and arts [12].
TeslaTouch [20] is a touch screen device which provides
a cutaneous feedback through electrovibration. The device
does not have any moving parts, but only provides the feed-
back when the user’s finger is moved across the surface.
The electrovibration principle is based on the control of
“electostatic friction between an instrumented touch surface
and the user’s finger”. The actuation is performed by exciting
a transparent electrode with a periodic electrical signal. The
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Adilkhanov et al.: Haptic Devices: Wearability-Based Taxonomy and Literature Review
haptic illusions of sliding over textured surfaces is rendered
by modulating the amplitude and frequency of the signal.
A skin-stretch device for fingertip was developed by So-
lazzi et al. [21]. The device conveys tangential forces in 2DoF
when the user’s finger is inserted in the thimble-like device.
The feedback is delivered by a system of shape memory alloy
(SMA) actuators and bias springs. The force displayed on the
fingertip is translated from SMA actuators through a textured
rubber end-effector (tactor). Based on its characteristics, this
device can be used for communicating directional cues and
rendering friction with virtual surfaces and objects.
Gallo et al. [22] designed a thermal feedback display for
teleoperation purposes. The device uses four individually
controlled peltier elements, and provides thermal feedback to
the user’s fingertip by heating up or cooling down the contact
surfaces. Due to its superior performance, water cooling was
preferred to air cooling despite the complexity of the water
pumping system.
Another tactile feedback display was presented by
Sarakoglou et al. [23]. The device is a 4×4 array of pins
(tactors) moving perpendicularly to the fingerpad with am-
plitude of 2 mm. Each tactor (with bandwidth of 7-19 Hz)
is actuated individually by a DC motor through a flexible
tendon transmission system. The device is integrated into a
teleoperation system, being attached at the master site to the
above-mentioned Omega kinesthetic feedback device.
The Fabric Yielding Display (FYD-2) [24], [25] is a tactile
feedback device for rendering softness characteristics of real
and artificial specimens. The actuation principle is based on
the regulation of the stretching state of the fabric. The ends of
the fabric belt are connected to rollers, each powered by a DC
motor. The belt stretching principle of FYD-2 is similar to the
one used for finger-worn devices: when the two motors rotate
towards outside, the fabric relaxes; when the two motors
rotate towards inside, the fabric’s stiffness increases. Also,
the device is able to deliver a shearing force to the user’s
finger when the motors rotate in the same direction. FYD-
2 has proven its efficiency in simulating different stiffness
values of various materials.
VibeRo [26] introduced another approach of rendering
virtual objects softness. The device combines vibrotactile
feedback and pseudo-haptic effect delivered through a HMD
for recreating the sensation of squeezing a soft granular
object. The vibration stimulus is created by modulating the
frequency proportionally to the rate of change of the applied
force at the fingertips. In turn, the pseudo-haptic feedback is
rendered by adjusting the rate of change of the shape of a soft
object seen in an HMD.
Asano et al. [27] developed a texture display with vi-
brotactile feedback. The researchers placed materials with
different textures on the top of the end-effector (acrylic plate)
connected to a voice coil actuator (VCA). The finger position
is captured by a camera. The idea is to modify the perceived
fine and macro roughness of material surfaces by stimulating
the user’s finger with vibrations.
Van Anh Ho et al. [28] created a grounded haptic display
for generating a pre-slide (incipient slippage) sensation on
the user’s fingertip for enhancement of grip forces control
during teleoperation tasks. The actuation principle of this
device is inspired by previous research on localized displace-
ment phenomena during pre-slide phase of soft object [30].
The device employs a bundle of stiff pins arranged in two
circles. Due to the specific placement, the pins at the outer
circles displace before and with higher velocity as compared
to those in the inner circles. The display provides effective lo-
calized skin displacement that enhances slippage perception.
The device presented in [29], PATCH (Pump-Actuated
Thermal Compression Haptics), uses water for providing
compression feedback. It comprises of two water tanks, hot
and cold, used for pump actuation to provide thermal feed-
back. The device has four actuators placed under the forearm
fabric sleeve. The desired temperature is set by mixing the
water from the two tanks in a single tube in specific propor-
tions. PATCH has a similar efficiency in displaying pulsing
and stroking patterns as a voice-coil-actuated sleeve.
B. HAND-HELD DEVICES
The devices that can be picked up and held within hands
without attaching straps are classified as hand-held devices
(see Table 2). Compared to grounded devices, they are
lighter, impose fewer constraints on movements and provide
a larger workspace. However, they cannot be worn and thus
do not give complete freedom of movement. Hand-held de-
vices can render kinesthetic or tactile feedback, or both at the
same time.
Well-known commercial examples of hand-held haptic
devices are game controllers for Sony PlayStation, Microsoft
Xbox video-game consoles, and tracking controllers for
Oculus Rift and HTC Vive VR systems. These controllers
enhance the user experience while holding them in hand
when playing video games. Traditional controllers provide
vibrotactile feedback to highlight certain events appearing on
the screen, for example collisions in car racing and battles,
and recoil when shooting. While the vibration stimulation
became a de-facto standard in such controllers, the articles
reviewed in this section consider a variety of different ap-
proaches for delivering haptic feedback. We divide hand-held
devices into two categories, based on the type of actuation.
More precisely, direct actuation devices act on the user’s hand
directly through the handle and the end-effector, whereas
indirect actuation devices change the center of gravity to
deliver different haptic cues.
1) Direct Actuation
Benko et al. [31] presented two hand-held controllers (Nor-
malTouch and TextureTouch) that enable users to feel 3D sur-
faces, textures and forces during interactions in VR applica-
tions. NormalTouch uses a 3D tiltable and extrudable Stewart
platform (actuated by three servomotors and equipped with
a force sensor) for delivering surface curvature cues to the
user’s finger resting on it. TextureTouch’s end-effector is a
6VOLUME 4, 2016
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content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2022.3202986
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Adilkhanov et al.: Haptic Devices: Wearability-Based Taxonomy and Literature Review
FIGURE 3: Examples of Direct and Indirect Actuation Type
hand-held devices.
4×4 pin-array placed under the user’s fingerpad for rendering
shapes of virtual objects and textures of virtual surfaces.
Despite the experimentally-proven effectiveness of these
two approaches compared to conventional vibrotactile feed-
back and visual-only feedback, some limitations are in place.
These include insufficient rendering of angles, forces and
heights by NormalTouch, while TextureTouch suffers from
its bulkiness and low pin resolution.
Another device for VR applications was shown in [32]. Re-
searchers upgraded a commercial hand-held controller (HTC
Vive’s controller) by augmenting its basic functionality (i.e.,
buttons, 6DoF movement control, thumb joysticks, trigger)
with kinesthetic and cutaneous feedback. The novel device,
named CLAW, can render haptic sensations such as grasping
a virtual object and touching a virtual surface through a
rotating arm for the index finger equipped with a VCA
for cutaneous rendering (i.e., variable stiffness of a grasped
virtual object, surface texture).
CapstanCrunch [33] is a device similar to CLAW in terms
of form-factor and purpose. It is a hand-grounded device
with a rotating arm for the index finger designed to render
the softness of a virtual object during touch and grasp.
Unlike CLAW, which integrates active actuation through a
strong servomotor, CapstanCrunch uses a variable-resistance
brake mechanism controlled by a small DC motor. As a
consequence, the user experiences a modulated resistance
depending on the applied force during finger closure, and
very low resistance as the finger opens. In [33], it was shown
that CapstanCrunch is better in rendering soft objects with
low stiffness values, whereas CLAW is more realistic in
rendering rigid objects.
Whitmire et al. [34] presented a Haptic Revolver - hand-
held controller for virtual reality. The device was designed
to deliver the tactile sensation of touching a virtual surface.
The structure of Haptic Revolver contains an actuated wheel
that moves perpendicularly to the fingertip direction to render
haptic cues of contact/non-contact with a surface, and rotates
to render the sensation of sliding across a virtual surface by
providing shear forces when the wheel is in contact with the
skin.
TORC [35] is a hand-held device for VR that can render
a wide range of haptic cues, including softness of virtual
objects and texture of virtual surfaces, and for the precise
manipulation of a grasped object by rendering fingers mo-
tions. The device was designed relying on a precision grasp.
The user’s index and middle fingers are placed and captured
with a Velcro strap on the finger rest part of the device. The
thumb is placed on the opposite side and can be freely moved
across a capacitance-based 2D trackpad for the user input. A
VCA is placed underneath each of the two rest parts (one for
the thumb, and the other for the index and middle finger) to
provide vibrotactile sensations.
A device with similar form-factor was presented by Walker
et al. [36]. This device, with cylindrical handle and kines-
thetic end-effector extending from the top, was designed to
convey sensations for motion guidance in 4DoF. The end-
effector is a pair of 2DoF pantograph mechanisms for thumb
and index fingers. The device provokes the users to move
and rotate their hands in various directions (up/down and
forward/backward, twist and tilt). Each joint of the 5-bar
linkages pantographs is powered by DC motors.
HaptiVec [37] is another hand-held controller, designed
for providing orientation (cardinal directions) in VE. It is is
made of two devices, one for each hand, which utilize 3×5
tactile pin arrays embedded into the handles so as to render
directional haptic pressure vectors. HapticVec is a cylindrical
shape controller with 15 solenoids with small cylindrical pin
contacts arranged in each handle, and with one analog 2-axis
thumb joystick attached to the top for user control.
PaCaPa (Prop that Alters Contact Angle on PAlm) [38] is
a compact box-shaped hand-held device for indirect (tool-
based) interaction in VR. It can render shape, size and
softness of a virtual object by opening and closing the two
sides (wings) of its body. The two wings, opened/closed at
the same angle by two servomotors, can open in the range 0°-
90°. The actuation provides a dynamically changed pressure
to palm and fingers, and imitates the angle between the virtual
stick and the hand.
While most hand-held haptic devices for VR are designed
for interaction with virtual objects without any reference to
real samples, Choi et al. [39] presented a mobile haptic tool
that combines active transient vibrations with pseudo-haptic
illusions to augment the perceived softness of haptic proxy
objects (i.e., real objects whose perception is modified in VR
interactions). The device was designed to be held with one
hand using a pointed grasp, with the index finger resting on a
finger rest platform. When a user makes the first contact with
a proxy object, a VCA placed under the platform generates a
transient vibration. The contact with the object and further
pressure applied by the user is captured by a capacitive
sensor. Then, the captured pressure is applied for rendering
a visuo-haptic illusion.
Sakr et al. [40], [48] proposed hand-held robotized tweez-
ers for microassembly, as hand-held haptic devices can find
their application not only in VR. The active tweezers can
be used as either an upgraded version of classical tweezers
providing a force feedback, or as a master device in a mi-
VOLUME 4, 2016 7
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content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2022.3202986
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Adilkhanov et al.: Haptic Devices: Wearability-Based Taxonomy and Literature Review
TABLE 2: Hand-Held Haptic Devices. * - weight without controllers or trackers.
Device Purpose Kinesthetic Feedback Cutaneous Feedback Actuators Mass
[31] surface shape rendering extrusion of
the platform
tilt of
the platform (x3) servomotors (Hitec HS-5035HD) 150
[31] rendering shape of virtual
objects and surface structure N/A 4x4 pin-array (x16) servomotors (Hitec HS-5035HD) 600 g
[32] grasping object,
touching surfaces, triggering
force feedback on
index finger
vibrotactile on
the index fingerpad
(x1) VCA + (x1) LRA +
(x1) servomotor (Hitec HSB-9370TH) 420 g
[33] softness of touched
and grasped objects resistance force N/A (x1) coreless motor (E-flite EFL9052) -
[34] touch, shear, texture,
and shape rendering N/A shear force
by rotating wheel
(x1) servomotor (Hitec HS-5070MH) +
(x1) DC motor (Faulhaber 1524-SR) 237 g
[35] in-hand interaction - texture,
compliance N/A vibrotactile (x2) VCA (Dayton Audio DAEX9-4SM) -
[36] guidance in medical training,
teleoperation and VE tangential forces N/A (x4) DC motors (Faulhaber 64:1) +
(x1) DC motor (Pololu 50:1) 76 g
[37] orientation in VE N/A pressure vectors
using pin array
(x15) solenoids in each hand
(DC0410, Yong Ci Neng Co.) -
[38] size, shape and stiffness of
a virtual object
opening/closing wings
to change the angle N/A (x2) servomotors (TowerPro SG92R) 65 g
[39] softness of haptic
proxy objects N/A vibrotactile (x1) VCA (Tectonic Elements
TEAX19C01-9) -
[40] tele-micromanipulation,
microassembly
force feedback
on fingertips N/A (x1) coreless motor
(DCX10L, Maxon Motor) 40 g
[41] rendering weight/shape of
virtual hand-tools DPHF - weight shifting N/A (x1) stepper motor (NEMA-14 type) 440 g
[42] rendering shape of
virtual hand-tools
DPHF - weight shifting
in 2D planar area N/A (x2) servomotors (Pololu 150:1 HPCB) +
(x2) servomotors (Pololu 50:1 HPCB) 400 g
[43] objects with different
scale/ material/fill state
DPHF - weight shifting +
air resistance N/A (x2) servomotor (MG996R) 598 g
[44] rendering forces of varios
directions and magnitudes
DPHF - propeller-induced
propulsive forcce N/A (x6) brushless motors
(2600KV T-Motor F40 III) 692 g
[45] dynamic weight
motion illusion
DPHF - propeller-induced
propulsive forcce N/A (x2) brushless motor (KV3900) 1069 g
[46] stiffness rendering extension/retraction of
the connecting cable
vibrotactile
(Vive controller)
(x2) servomotors (Actuonix L12-R
Micro Linear Servo) *673 g
[46] stiffness rendering lock/unlock of
ball joints and hinge
vibrotactile
(Vive controller) (x3) servomotors (FEETECH FS5115M) *793 g
[46] rendering midair
impassable surface
lock/unlock of ball joints
and ratchet mechanism
vibrotactile
(Vive controller)
(x2) servomotors (FEETECH FS5115M) +
(x2) servomotors (Hitec HS-35HD) *651 g
[47] rendering virtual objects
in hand on demand
force feedback
by pivoting handle
vibrotactile feedback
from inside the handle
(x1) servomotor(Hitec HS-7115TH) +
(x1) VCA *188 g
cromanipulation system to provide the motion control of a
slave robot. The master tool is an ordinary tweezer equipped
with a DC motor that provides force feedback and controls
the opening of branches, and multiple sensors like strain
gauges, force sensor under a user’s fingertip and markers for
its motion capture system. This interface aims to help the
operator to feel micro-sized objects by scaling up the robotic
gripper work area to a human scale.
2) Indirect Actuation
Rendering multiple virtual hand tools (e.g. a sword, a crank,
a baseball bat) with various shapes is a rather difficult task
that cannot be solved with conventional VR controllers. An
obvious way of solving this problem is to use a different
proxy object for each virtual tool, which might not be an
efficient solution in many cases.
An alternative approach to avoid this issue is Dynamic
Passive Haptic Feedback (DPHF), introduced by Zenner and
Krüger [41]. DPHF is a mix of active haptic systems (which
directly actuate the human limb) and haptic proxy objects.
Shifty, presented in [41] is an example of device using DPHF.
The rod-shaped device shifts the position of its center of mass
(“weight shifting”) using one stepper motor placed on the
grip end of the device. This in turn modifies the moment of
inertia exerted on the user’s hand, to enhance the perception
of virtual objects that are changing in shape (length and
thickness) and weight. Indeed, psychological studies of the
human shape perception mechanism have shown that weight
shifting mechanisms can alter the perception of an object
shape without even seeing it [49]–[53].
Transcalibur [42] is another weight-shifting device for
imitation of various virtual hand-tools (e.g., swords, guns,
crossbows), able to dynamically present 2D shapes by chang-
ing its mass properties on a planar area. The authors called
this kind of illusion Haptic Shape Illusion. Transcalibur
resembles a handle with two rotatable arms with a maximum
rotation angle of 90°. A weighting module is attached to each
arm and can slide along it.
Another hand-held haptic device that can give a sensation
of operating virtual objects with various shapes and sizes is
Drag:on [43]. Drag:on uses its pair of wings to dynamically
change its surface. Two servomotors can independently open
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Adilkhanov et al.: Haptic Devices: Wearability-Based Taxonomy and Literature Review
and close the fans to shift the weight and increase/decrease
the air resistance that occurs at the controller during hand
motions. The device can be used to enhance the realism of
VR sport experiences, and of other physical interactions such
as rowing, swimming or driving. Its main limitation is the
need to keep it in motion for perceiving the haptic feedback.
Drag:on was not the first device to use air resistance for un-
grounded force feedback. Researchers have investigated the
implementation of propeller propulsion to create thrust via air
flow [44], [45]. The idea is to equip a handle held by a user
with propellers, so that the user’s wrist becomes a pivot point
experiencing torque applied by the propeller propulsion. The
modulation of the propeller speed and rotational direction
causes a dynamic force feedback, giving a perception of
change in the center of mass. The main difference with the
above-mentioned indirect actuation devices is that propeller-
based devices are capable of delivering continuous force
feedback creating a dynamic weight motion illusion [45]
rather than a shape illusion [42].
Heo et al. [44] introduced a hand-held VR controller that
can deliver a large physical force in 3D. The device, named
Thor’s Hammer, has six brushless motors and accompanying
tri-blade propellers that generate bi-directional thrust (up to
4 N) in three axes. Motors and propellers are mounted on
the sides of a carbon fiber pipe cubic cage. Thor’s Hammer
demonstrated enhanced realism of VR experience such as
holding a virtual stick in flowing water, herding a sheep
and simulating different weights. Despite its high rendering
accuracy (RMSE of less than 0.11 N and 3.degree), com-
pared to other devices the device has high actuation latency
(309.4 ms), a large weight and size, high power consumption,
and noise.
Aero-plane [45] uses only two jet-propellers, and provides
a even greater thrust (up to 14 N). The device resembles
a cylindrical handle with the jet propellers at the one end,
and a counterbalancing weight at the other end. Despite the
parallel direction of propeller thrust, the independent control
of the propeller provides the user with a torque around the
handle axis. Therefore, Aero-plane is able to provide the
haptic illusions of a shifting weight on a 2D plane. The device
showed increased immersion level in VR applications such
as rolling a ball on a 2D plane, operating virtual food with
different virtual cooking utensils, and fishing. Aero-plane
shares the same practical disadvantages as Thor’s Hammer.
Thus far we have reviewed hand-held devices designed to
be used with one hand or with two independent hands. In-
stead, Strasnick et al. [46] focused on rendering haptic feed-
back between two hands for bimanual interactions. Examples
provided by the authors are driving with a virtual steering
wheel and operations with two-handed tools or weapons.
The system with two controllers physically linked through
an electro-mechanically actuated connector is named Haptic
Links. There are three prototypes of Haptic Links - Chain,
Layer-Hinge and Ratchet-Hinge - which are differ in terms
of linkage design.
Another haptic device for VR that utilizes a proxy object
FIGURE 4: Schematics of different groundings of haptic
devices: (a) world-grounded (i.e. tabletop) haptic device,
(b) body-grounded kinesthetic device (i.e. exoskeleton), (c)
finger-worn cutaneous device. The reaction forces are shown
in green, actuation force in violet. Adapted from [9].
is PIVOT [47]. Although the device is wrist-worn, it also
comprises of a pivoting handle to be placed in the user’s
hand, and is thus a hybrid between wrist-worn and hand-
held devices. In synchronization with VE, the motorized
hinge is able to quickly bring/move out the generic haptic
handle to/from the user’s hand, thus simulating the grasping
or throwing of a virtual object. Also, PIVOT can to exert
forces in both directions along the axis normal to the palm
surface, imitating gravity, inertia or drag.
C. EXOSKELETONS
The most typical form of wearable haptic devices are haptic
gloves and exoskeleton systems (or, in short, exoskeletons).
The main difference between them is that not necessarily all
haptic gloves have exoskeletal structure, and not necessarily
all exoskeletal systems are in the form of a glove. These
devices are aimed at rendering kinesthetic haptic feedback
while being grounded to the user’s body [9]. Please notice
that gloves and exoskeletons that are used as prosthetic
devices or for the enhancement of lost capabilities of disabled
people are out of the scope of this review paper, also due to
space limitation.
The main drawback of body-grounded haptics is that the
wearers feel two types of forces applied to their bodies: the
force applied to the desired point of haptic stimulation, and
an undesired reaction force at the point of attachment to the
body, which counterbalances the first one (Fig. 4b). In order
to make the reaction force less perceivable, one typically
designs the device to distribute it onto a large contact surface.
Also, moving the body-grounded base as close as possible
to the point of application of the haptic stimulus improves
wearability (Fig. 4c). However, as mentioned in [10], a
very close location of the base and the end-effector to each
other makes the device only provide tactile feedback, and all
kinesthetic properties disappear.
Present commercially available glove-based haptic ex-
oskeletons are Dexmo (Dextra Robotics, China) and Cyber-
Grasp (CyberGlove Systems LLC, USA). These devices pro-
vide realistic grasping sensation by means of resistive forces.
The factors that prevent widespread use of these devices
are practical limitations such as careful putting on/off, low
versatility to different user sizes, and expensiveness due to
VOLUME 4, 2016 9
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content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2022.3202986
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Adilkhanov et al.: Haptic Devices: Wearability-Based Taxonomy and Literature Review
FIGURE 5: Examples of Resistive Force (left column), Lock-
ing Mechanism (central column) and Pneumatic Actuation
(right column) type haptic gloves and exoskeleton devices.
number and complexity of mechanisms.
The previous review papers on haptic gloves and exoskele-
tons were considering a classification by haptic stimuli [9],
actuation technology of haptic gloves for VR [11], pros
and cons of existing force feedback gloves, and the design
guidelines [10] and requirements of hand exoskeletons [54].
Pacchierotti et al. [9] defined exoskeletons as “a type of
haptic interface which is grounded to the body”. Their review
paper focused on two groups of exoskeleton devices, based
on kinesthetic and vibrotactile feedback.
In a review on haptic gloves for VR by Perret et al. [11], the
authors categorized the devices into three groups - traditional
gloves, thimbles and exoskeletons. This review is focused on
commercially available prototypes, and discusses the design
challenges facing this technology.
The most recent and detailed review on exoskeletons and
gloves was published in 2019 by Wang et al. [10]. The
paper presents classification of both research prototypes and
commercially available haptic gloves, and design guidelines
for the hardware components of force feedback gloves (actu-
ation, sensing, transmission, control and mechanical struc-
ture), referring to anatomical features of the human hand.
Wang et al. classified the kinesthetic gloves by the location of
the actuation - ground-based, dorsal-based, palm-based, and
digit-based gloves. This approach is intuitive and reasonable
due to the strong effect of the location of the actuation
on force feedback performance and device characteristics
(weight and size).
As an alternative approach to [10], in this review we
propose to classify exoskeleton systems and haptic gloves
by means of delivering haptic cues - through resistive force,
locking mechanisms or pneumatic actuation. All the re-
viewed devices, summarized in Table 3, explored different
approaches of delivering the sensation of grasping or grip-
ping virtual objects.
1) Resistive Force
This type of haptic gloves and exoskeletons provide a force
feedback by actuating motors that generate resistive force,
whose key feature is to be bidirectional and non-discrete.
Therefore, these devices can provide the haptic illusion of
various size, shape and stiffness levels of graspable virtual
objects.
Pierce et al. [55] developed a two-finger-wearable haptic
device with both kinesthetic and tactile feedback designed
for teleoperation over a robotic gripper. The device represents
a gripper-style rigid structure which covers the user’s index
finger and thumb from the dorsal side. The angle between
thumb and index fingers is controlled via a 1-DoF revolute
joint actuated by a geared DC motor. There are movable rigid
platforms at both fingertips, which provide pressure force and
vibrotactile feedback via voice coil actuators.
Another finger-thumb style wearable exoskeleton device
was proposed by Cempini et al. [56]. However, this device
has more DoF and more complex kinematics compared to the
device proposed in [55], due to its modular structure. There
are sixteen DoF in total - seven for the index finger (three
passive, four active) and nine for the thumb (six passive,
three active). The force is applied to carpal, metacarpal, and
phalangeal joints (all being of revolute type) through a cable-
driven actuation system.
Dexmo [57] is a hand exoskeleton system with force feed-
back for rendering the sensation of grasping a virtual object.
The device has simple and lightweight design and consists
of the following main parts: controller, force feedback units,
rigid connectors and finger caps. Dexmo is worn on the dorsal
side of the hand, being attached to the fingertips with finger
caps and to the palm with a strap. The main controller is in
the central unit, placed on the back of the palm. Each of the
five finger caps is connected to the central unit through a rigid
connectors and the force feedback unit. The force feedback
unit consists of two rotational sensors, which track the angle
of upper and lower connectors, and a micro servomotor that
locks the joints (rotation of both connectors) in response to
a scene in the VE. Thus, Dexmo can only provide a binary
force feedback not being able to render the stiffness of virtual
objects.
Jo et al. [58] developed a three-finger exoskeleton system
for VR to render the stiffness of various virtual objects. The
system is similar to Dexmo in terms of form-factor - palm-
based central unit and rigid linkages (5 DoF) for fingertips.
However, this device is designed only for three fingers -
thumb, index and middle fingers. The device is connected
only to the fingertips through a ring with click buckle for
ease of wearability. Each fingertip is powered by a DC motor
located on the dorsum of the hand.
ExoTen-Glove [59] is a haptic glove for VR applications
based on twisted string actuation (TSA), for rendering the
sensation of grasping virtual objects with various stiffness.
Generally, a TSA system is an actuating module consisting
of a high speed and low torque DC motor and a twisted
string, which connects the motor with the load (tendon). The
rotation of the DC motors is transformed into a linear motion
at the load side by the contraction of the spring. Such actu-
ation approach allows for lighter and less bulky exoskeleton
structure as compared to [55], [56], [58]. ExoTen-Glove has
10 VOLUME 4, 2016
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content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2022.3202986
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Adilkhanov et al.: Haptic Devices: Wearability-Based Taxonomy and Literature Review
TABLE 3: Exoskeletons and Gloves. * - weight without actuating block placed on the forearm.
Device Type Purpose/Haptic Illusion Kinesthetic Feedback Cutaneous Feedback Max Force[N] Mass[g]
[55] resistive force teleoperation (x1) DC motor vibrotactile &
normal force 6.7 -
[56] resistive force HRI (x2) DC motor + cables N/A -438*
[57] resistive force object grasping (x5) micro servomotors N/A -270
[58] resistive force object grasping (x3) DC motors N/A 2 488
[59] resistive force object grasping (x2) DC motors + TSA system N/A 80 360
[60] resistive force teleoperation (x1) active Delta robot structure N/A 5 2,224
[61] locking mechanism object grasping (x3) DC motors N/A 106 55
[62] locking mechanism weight & stiffness
of grasped object (x2) DC motors vibrotactile - 65
[63] locking mechanism object grasping (x2) ES brakes vibrotactile 20 8
[64] pneumatic actuation stiffness of
grasped object (x2) jamming pads/tubes vibrotactile 7 70
[65] pneumatic actuation object grasping (x2) soft elastomer actuators N/A 2.1 30.8
[66] pneumatic actuation stiffness of
grasped object (x4) air-jet nozzles N/A 0.7 175
two TSA modules - one for the thumb and one for the other
fingers - placed on the forearm. The tendons are attached to
a commercial soft glove.
While the above-mentioned exoskeleton devices focus on
providing force feedback to the user’s fingers, W∆[60] is
designed for providing force feedback to the user hand back
(wrist). The exoskeletal system is worn on the user’s forearm
and provides the actuation through a hybrid serial-parallel
kinematic structure and passive gimbals. W∆has shown its
efficiency in teleoperation by rendering contact forces sensed
by a controlled robot end-effector.
2) Locking Mechanisms
The working principle of this type of haptic gloves and
exoskeletons is that a locking mechanism actuated by a motor
makes the system rigid, restricting the movement of the user’s
proximities. This type of actuation is unidirectional and can
only conveys the sensation of rigid virtual objects.
Wolverine is an exoskeleton force-feedback device pre-
sented in [61], designed to deliver kinesthetic feedback in a
specific configuration - between the fingers (index, middle
and ring) and thumb - to simulate grasping of rigid objects
in VR. The base of the device (microcontroller, motor driver,
inertial measurement unit (IMU) and battery) is mounted on
the thumb, whereas each of three other fingertips is attached
to a sliding mount. The thumb and the other fingers are
interconnected through an exoskeleton structure consisting of
carbon fiber rods with sliding mounts moving along them.
The rods are linked to the base with ball joints (3DoF).
Each sliding mount is equipped with a braking mechanism
actuated by a DC motor at the moment when it is required
to simulate a grasp. Since Wolverine uses the same passive
actuation principle as Dexmo, stiffness rendering is also
impossible with Wolverine.
Grabity [62] represents another approach for rendering
virtual object grasping with a haptic exoskeleton. The device
with a gripper-like form-factor [55], [56] combines a uni-
directional brake mechanism [61] with vibrotactile feedback.
The base of the device is mounted on the thumb, whereas
the sliding part is mounted on the index finger. Both the
base and the sliding part have a pad for fingers with a
linear VCA attached to the fingertips. The addition of a pair
of vibromotors allows rendering touch and gravity (pulling
force) sensations via symmetric and asymmetric vibrational
stimuli, respectively.
Another device with locking mechanism was designed in
the form of standard exoskeletons for the hand. The key unit
of DextrES [63] consists of electrostatic (ES) brakes, which
can generate a resistive force on the wearer’s index finger
and thumb. Each ES brake is made of metal strips that slide
freely on each other and do not constrain limbs movement
when no voltage is applied. Being mounted to a textile glove
and attached to the back of the thumb and index finger,
the ES clutches block the human joints movement when the
control voltage is applied, thus simulating the object grasping
sensation. In addition to the kinesthetic feedback, DextrES
utilizes vibromotors attached to the fingertips for enhancing
the haptic illusion of grasping.
3) Pneumatic Actuation
This type of devices use pneumatic actuation (using either a
pump or a compressor) for delivering force feedback, via soft
actuators and tubes attached to a fabric glove.
Zubrycki and Granosik [64] presented a haptic glove that
uses the jamming principle for providing force feedback.
The key feature of this device is a combination of jamming
tubes (or jamming pads) and vibration motors. The jamming
elements are elastic actuators made of latex rubber. These
elements are placed on the inner side of the hand joints
and, being controlled by the vacuum pressure, can resist
or block movement of the user’s joint. The combination
of jamming mechanisms and vibrotactile stimuli provides
the user with the sensation of grasping virtual objects with
various stiffness levels. The disadvantages of this approach
are the need for a bulky pneumatic system (which leads to a
limited workspace), and considerable actuation time (0.5 s).
In contrast, Zhang et al. [65] demonstrated an approach
with pneumatic actuation using high pressure instead of
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Adilkhanov et al.: Haptic Devices: Wearability-Based Taxonomy and Literature Review
vacuum as in [64]. Silicone elastomer actuators, placed inside
a textile glove, are attached to the dorsal side of thumb and
index fingers. During high air-pressure supply, the actuators
bend creating a resistive force on the fingertips.
Besides pneumatic (low/high pressure) soft actuation, air
flow is also used for providing air-jet force-feedback: this is
the case of ω-jet [66], a glove without exoskeletal structure
able to convey stiffness and elasticity sensations while inter-
acting with virtual balls of different size and stiffness. The
device is equipped with four nozzles (for index, middle, ring
and little fingers) for air jetting and four bend sensors for
finger angle detection. The nozzles are attached to the dorsal
side of the fingers such that they slightly protrude beyond the
fingertip. The bend sensors are positioned along the vental
side of the fingers.
While the haptic sensations delivered by haptic gloves
and exoskeletons can be of high fidelity, they have some
practical limitations. The weight of such devices is compar-
atively high, which causes fatigue over periods of more than
one hour [47]. Typically haptic gloves and exoskeletons are
cumbersome and thus often limit the full range of wearer’s
motion. In addition, it requires a long time to put them on
and to take them off [32].
D. FINGER-WORN DEVICES
Finger-worn haptic devices (also known as thimbles, and
listed in Table 4) mostly focus on the tactile stimulation of
the fingerpads. Indeed, the latter show one of the highest
density of tactile receptors within the human body [6], and
most dexterous manipulation activities involve our fingertips
[67]. This is especially true for the index finger, which is
involved in most actions and gestures.
During fingerpad-object interaction, mechanoreceptors are
stimulated by different physical cues due to change in contact
surface, local surface orientation and skin stretch. Thus, most
haptic thimbles are designed relying on these principles, and
based on two main approaches: moving platform mecha-
nisms [3], [7], [68]–[78], and shearing belt mechanisms [79]–
[82]. Other less common approaches are moving tactors [83],
and systems with electrical [84], thermal [76], vibration [85],
[86] and pneumatic [87] stimulation.
1) Moving Platform
Typically, moving-platform type devices possess a parallel
mechanical structure (Fig. 6). The whole system can be
separated into two parts - base and end-effector (moving
platform). The base is placed on the nail side on the last
phalanx of a finger, and supports joints and actuators. It is
fastened with a strap on the intermediate (middle) phalanx.
On the volar side of the finger, an end-effector acts on the
fingerpad providing cutaneous feedback through mechanical
skin deformation. The end-effector usually moves with 3 DoF
- via a combination of rotational and prismatic joints - cover-
ing most of the fingerpad.
The overall trend in the development of moving plate type
finger-worn haptic devices is shown in Fig. 6. The develop-
FIGURE 6: Finger-worn haptic devices of a moving plate
type: (a) a heavy and bulky device with sheathed tendon
actuation [68], (b) lighter and more compact devices with
actuation through DC motors and gears/cables [69], (c) light
and compact devices actuation through servomotors and rigid
links [74].
ment of haptic thimbles of this type started from creating
portable versions of the previously-available bulky grounded
haptic thimbles (see, e.g, [92]). For example, Solazzi et
al. [68] created Active Thimble for virtual shape exploration
making it wearable and mobile, but still cumbersome due to
the use of a heavy motor pack with sheathed tendon actuation
of the end-effector. Later, a decrease in size and weight of
devices was achieved through the use of cables [7], [88] or
gears [73] controlled by light DC motors. The end-effector
of Haptic Thimble presented in [73] is equipped with a VCA
for surface edges and texture rendering.
The authors of [7], [88] showed similar fingertip haptic
devices. Their approach consists of controlling position and
orientation of the end-effector through wires whose lengths
and strains are tuned by three DC motors. Later on, these
DC motors were replaced by servomotors [3], [77], [93].
In [3], [73], [77], a vibromotor is mounted on the mobile
platform for providing rendering surface features such as
edges, texture and stiffness.
The authors of [70], [71] presented two haptic thimbles
in which the cable links between base and mobile platforms
are substituted with rigid 3D-printed limbs. These new pro-
totypes have a 3-DoF kinematic chain which allows compact
dimensions with minimum encumbrance within the hand
workspace and mechanical interference with other fingers.
The devices show increased performance compared to cable-
driven moving platform devices in terms of maximum normal
force exerted on user’s fingertip (up to 4.7 N).
Later, the device of [70] was improved by adding vibro-
tactile feedback under the moving plate, which gives the
perception of surface softness [89]. Furthermore in [78] is
the device of [89] with increased functionality - addition of 1-
DoF kinesthetic finger module for better virtual manipulation
performance. The fingertip module is grounded on the distal
phalanx, whereas the kinesthetic module with an additional
servomotor is fixed on the proximal phalanx. The two mod-
ules are connected through a rigid rod that provides force
stimuli to the proximal and distal interphalangeal joints.
A rubber tactor is mounted on a moving platform in [74],
[75], [83] for better shear force provision. In [75] the tactor is
placed on a delta parallel mechanism actuated with a motor-
linkage tether driven by two DC motors, able to exert the
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Adilkhanov et al.: Haptic Devices: Wearability-Based Taxonomy and Literature Review
TABLE 4: Finger-Worn Haptic Devices. Type: MP - moving platform, SB - shearing belt, OT - other types.
Device Type Haptic Feedback Haptic Illusion VE Actuators Mass
[68] MP skin stretch surface shape - (x4) DC motors (Faulhaber 1524) +
(x1) VCA (BEI Kimco LA08-10) 256 g
[73] MP skin stretch +
vibrotactile surface shape & texture VR (x1) VCA +
(x2) servomotors 30 g
[88] MP skin stretch surface curvature - (x3) DC motors (Faulhaber 0615S) 30 g
[7] MP skin stretch stiffness - (x3) DC motors (Faulhaber 0615S) 35 g
[3] MP skin stretch +
vibrotactile palpation (robotic surgery) VR (x3) servomotors (Pololu SubMicro) +
(x1) vibromotor (Force Reactor, Alps Electric) -
[77] MP skin stretch +
vibrotactile object manipulation VR (x1) ERM vibromotor (VPM2, Solarbotics) 10 g
[71] MP skin stretch surface exploration VR (x3) servomotors (Turnigy TS531A) -
[70] MP skin stretch surface orientation -(x3) servomotors (Turnigy TGY-1370A) -
[89] MP skin stretch +
vibrotactile surface exploration, softness VR (x3) servomotors (HiTech HS-5035HD) 25 g
[74] MP skin stretch object manipulation VR (x3) servomotors (HK-282A RC) 16 g
[75] MP skin stretch weight, stiffness, friction VR (x2) DC motors (Faulhaber 0615S) 32 g
[78] MP skin stretch +
force feedback teleoperation VR - 42 g
[83] MP skin stretch surface exploration & weight VR (x2) DC motors (Maxon RE8) 22 g
[79] SB skin stretch gravity & grip force -(x2) DC motors (Maxon RE10) 35 g
[80] SB skin stretch stiffness VR/AR (x2) servomotors (HiTech HS-40) 15 g
[85] OT vibrotactile stiffness VR (x1) ERM vibromotor (Precision Microdrives 310-113) -
[86] OT vibrotactile surface texture VR/AR (x1) VCA (Bone Conductor Transducer, Adafruit) 9.6 g
[84] OT vibrotactile +
electrical
hardness, friction, fine
& macro roughness -(x1) DC motor (Maxon 118386) +
(x1) 4×5 electrode array 15 g
[90] OT force feedback contact & softness - HC-DEAs (VHB 4910, 3M) -
[91] OT skin stretch contact/non-contact - TCP actuators 14 g
normal force up to 7.5 N. On the other hand, in HapTip [83],
a tactor is mounted on a static platform under the fingertip
and can only provide shear force (up to 3 N). Wearing such
skin-stretch devices on multiple fingers gives the ability to
render a feeling of weight of a virtual object and roughness
of virtual surfaces.
Lim et al. [94] presented a haptic device with a moving
actuator. The tactor is set into motion by SMA actuators
through two transmission mechanisms: a 3-DoF tip-tilt and
2-DoF planar 3D-printed springs. The choice of SMA-type
actuators was due to their mechanical simplicity, shear defor-
mation of the fingertip skin, lightweight and silent operation
with smooth motion. The designed 5-DoF fingerpad device
can provide a reliable weight sensation of virtual objects.
2) Shearing Belt
Another popular approach of providing haptic cues to user’s
fingerpad is based on the use of a fabric belt. The first device
of this type was introduced by Minamizawa et al. [79]. Due
to the fingerpads deformation caused by the shearing belt, the
device can reproduce a realistic gravity sensation even in the
absence of proprioceptive stimuli on wrist or arm.
Devices of this type consist of a pair of DC motors placed
on the platform fixed to the nail side of the user’s finger, and
a belt that is in contact with the fingerpad (Fig. 7). The ends
of the belt are attached to two pulleys actuated by the DC
motors. When the motors rotate in the same direction, the
belt generates shearing stress on the fingertip, while, when
the motors rotate in opposite directions, the belt exerts normal
force on the fingertip.
In hRing, Pacchierotti et al. [80] replaced the DC motors
used in [79] with servomotors, which allows controlling
the amount of skin deformation, proportional to the motor
position. hRing provides cutaneous stimuli to the proximal
phalanx of the finger instead of the fingertip, which makes the
user’s fingertips free to interact with the real environments
(e.g., in AR applications). In [82], [95], , it was shown that
such haptic stimulation can considerably alter the perceived
stiffness of real objects, even when the tactile stimuli are not
delivered at the contact point.
Bianchi et al. [81], [96] went further and presented the
Wearable Fabric Yielding Display (W-FYD), a fabric-based
finger-worn display for multi-cue delivery. The device aims
to enable both active and passive softness exploration. From
the mechanical perspective, it differs from previous rolling
fabric-belt fingertip devices by addition of a lifting mecha-
nism that independently regulates the pressure exerted by the
belt on the fingerpad. However, its mechanical complexity
leads to larger normal forces applied to the fingerpad (8.5 N)
as well as an increase in weight and dimensions.
Aoki et al. [97] presented a device with form-factor similar
to a shearing-belt type devices. However, a thin wire was
used instead of a belt to decrease weight. The wire is moved
only perpendicularly to the fingerpad, exerting a force up to
40 mN.
Overall, thimbles of this type are very simple, compact
and light. They can be used in multi-finger combination,
and can provide the sensation of weight, inertia and stiffness
while grasping a virtual object. Their main disadvantage -
impairing hand mobility - comes from the need for well
tightening in order to avoid instability during shear force
display, and this blocks the phalanges articulation.
VOLUME 4, 2016 13
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Adilkhanov et al.: Haptic Devices: Wearability-Based Taxonomy and Literature Review
FIGURE 7: Working principle of shearing belt type haptic
devices.
3) Other types
Vibrotactile stimulus is one of the most popular types of
cutaneous feedback due to the small and lightweight form
factor of vibrotactile actuators that allows to develop highly-
wearable interfaces [9].
Maereg et al. [85] proposed to use vibrotactile feedback
directly on fingertips without using moving platforms. The
haptic setup consists of five eccentric rotating mass (ERM)
vibrotactile actuators, one actuator per finger, fixed on fin-
gerpads via straps. The frequency of vibrations is modulated
proportionally to the interaction force. In combination with
visual feedback provided through an HMD, the tactile device
can give the sensation of tapping a stiff object in the VE.
The controller is placed on the wrist, which makes the overall
structure highly wearable and wireless.
A finger-worn device utilizing vibration feedback in com-
bination with normal and shear force feedback was presented
in [98]. The haptic feedback is delivered through the use
of magnetic field actuation. The device structure consists of
a plastic cuboid casing with its top side being soft (nitrile
rubber). The casing is filled with ferro-fluid and attached
to the distal phalanx. The ferro-fluid is used for magnetic
field enhancement, and lubrication of a neodymium magnet
(NMEF) placed inside the casing. The feedback is delivered
to the fingertip with the movement of the NMEF. In turn, the
NMEF movement (normal to the fingertip and rotational) is
caused by control of voltage of solenoid winded around the
casing and the orientation of an external neodymium magnet
(ENM). The orientation of ENM is regulated by a DC motor
attached to the bottom side of the casing.
Most of the previously described finger-worn haptic de-
vices focuses on providing tactile stimuli to the most sensitive
part of the skin - the fingerpad. Gaudeni et al. [86] presented
a haptic ring that provides a vibrotactile feedback, and can
be worn on three different locations: fingertip, dorsal side
of proximal phalanx, and wrist. The device is composed of
a VCA enclosed in a 3D-printed housing that can be fixed
to a limb. In [86], it was concluded that the vibrotactile
cues provided by the haptic ring on the proximal phalanx
are sufficient for a user to distinguish between different
surface textures. Thus, this type of design can help freeing
the fingertips for other tasks.
Several studies have proposed the use of direct electrical
stimulation of the nerves to achieve high responsiveness
of skin and small device size of a device. However, it is
still challenging to reproduce realistic tactile cues using this
method. Thus, in 2017, Yem and Kajimoto [84] developed
a finger-worn tactile device called FinGAR (Finger Glove
for Augmented Reality). The device uses a combination of
electrical and mechanical (vibrational) actuation that gives
four different stimulation modes: skin deformation, high-
frequency vibration, anodic and cathodic stimulation. Thus,
the sensation of four tactile dimensions - macro roughness
and hardness (affected by low-frequency vibration and ca-
thodic stimulation), friction and fine roughness (affected by
high-frequency vibration and anodic stimulation) - can be
reproduced by combination of these modes. The “glove”
consists of three FinGAR devices to be worn on the thumb,
index and middle fingers. Every single thimble is made of
three main parts - a 3D-printed base that grips both sides of
the distal phalanx, a DC motor and a 4×5 electrode array
film.
All the haptic devices described above employed a variety
of different actuators that provide different tactile sensations
(such as contact with objects and surfaces, and properties like
roughness, shape and softness) through rigid end-effectors.
Stiff surface end-effectors, suitable for shape rendering, can-
not effectively render softness perception, which is a major
goal for modern haptic interfaces. According to Srinivasan
and LaMotte [99], Moscatelli et al. [100] and Dhong et
al. [101], both contact area and indentation depth must be
controlled to render the stiffness of virtual deformable ob-
jects. Since the feedback applied by stiff surfaces controls
only the indentation of the skin, the most effective strategy
is to use soft interfaces such as dielectric elastomer actuators
(DEAs), electrostatic actuators and pneumatic actuators.
Frediani et al. [90] introduced a wearable tactile display for
the fingertip which is able to simulate contact with soft bodies
in the VE using a soft actuator. The new approach is based
on DEAs, which are intrinsically soft, compact, lightweight,
and silent during operation. The device is mounted on the
user’s fingertip with the actuator being integrated within a
plastic case and placed under the user’s fingerpad. The main
drawback of using DEAs is the need for high driving voltages
(4.5 kV).
Chossat et al. [91] proposed a finger-worn skin-stretch
device based on a soft elastomeric adhesive skin and twisted
and coiled polyethylene (TCP) actuators, which had not been
considered for wearable devices before. The haptic skin is
worn on the back side of the index finger. The skin can be
pulled via nine retainers. When heated, the TCP actuators
contract and pull the retainers; the TCP is released when
cooled down. The bandwidth of such system is rather low
and thus TCP-based stimuli are less effective in interactions
with a virtual wall than VCA-based stimuli.
14 VOLUME 4, 2016
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Adilkhanov et al.: Haptic Devices: Wearability-Based Taxonomy and Literature Review
FIGURE 8: Schematics of three actuation types of arm-
worn haptic devices put on the cross-section of the forearm:
(a) vibrotactile feedback, (b) skin stretch and compression
feedback, (c) thermal feedback.
E. ARM-WORN DEVICES
Arms as possible location for haptic feedback have been used
less than hands, possibly due to lower density of mechanore-
ceptors [102]. Indeed, since the human tactile acuity varies
across the skin surface, relocating haptic cues away from the
actual location where they are typically experienced (mainly,
fingertips) may degrade the sense of realism. This is probably
the reason why wrist-worn bracelet-type devices have been
investigated more recently than other types of wearable hap-
tic systems. Bracelets, however, have the advantage of freeing
the fingers for other tasks, which makes it possible for users
to easily switch between VE and real world, or to change the
tactile feeling of real objects by augmenting them with virtual
textures [86].
The application of these haptic devices can be split
into two categories: guiding (e.g. navigation, telemanip-
ulation) [103]–[108] and enhancement of tactile percep-
tion [109]–[112]. In order to properly use devices of the first
category, the user has to complete a training phase. Instead,
devices of the second category do not require such phase, but
have to provide a strong haptic stimulus that can be easily
perceived.
In terms of type of stimuli, wrist-worn bracelet-type de-
vices can be divided into vibrotactile, skin stretch and com-
pression, and thermal, as detailed in the following.
1) Vibrotactile Feedback
As observed for previous tactile devices discussed in this
survey, vibrotactile stimulation has been preferred by many
haptic wristband developers due to the compact size and
the light weight of the vibration actuators. Thus, wrist-worn
haptic devices of this type are mostly used for applications
within physical activities. For example, the authors of [103]
used haptic bands called Hapi Bands for guidance in Yoga
postures.
Panëels et al. [104] introduced a tactile bracelet for nav-
igation tasks. The device has the form of a wristwatch, and
is equipped with six electromagnetic actuators arranged in
circle that provide vibrotactile feedback. The navigational
information is delivered via combination of vibration patterns
including duration, pauses, frequency, amplitude, position
and number of tactors.
Another haptic wristband for navigation was described in
[105], where vibrotactile feedback is provided to navigate
a user during human-robot guidance. The actuation is per-
formed by three cylindrical vibro-motors, which provide a
haptic signal when the human deviates from the planned
trajectory.
The arm-worn device presented in [115] uses vibrotactile
feedback for haptic communication. The device consists of
a sleeve with six VCAs placed in Braille layout. Language
messages are encoded through vibrotactile patterns. The re-
sults of the presented experiments show that it is possible
to use haptic devices as an alternative to visual and auditory
communication channels. Prior to the usage of the device, a
training phase is required to learn haptic cues representing
nine phonemes.
Haptic wristbands have shown effectiveness in performing
teleoperation tasks. Bimbo et al. [113] presented a haptic
system for operation in cluttered environments. The wear-
able (master) part of the system consists of two vibrotactile
bracelets, worn on the user’s forearm and upper arm. Four
vibration motors, evenly positioned around the arm, provide
directional information about the collisions sensed by the
slave system (IIT/Pisa SoftHand and Universal Robot arm).
The amplitude of the vibration stimuli is proportional to the
force of the collision.
Zhao et al. [114] have introduced an approach of providing
vibration-like feedback using dielectric elastomer actuation.
A 2×2 array of dielectric elastomer actuators is placed inside
a textile sleeve. Each actuator is controlled independently and
provides normal force to the wearer’s skin on the forearm
when a voltage is applied. The soft actuators have moderate
bandwidth (up to over 200 Hz) and actuation force of 1 N.
In the field of AR/VR hand interactions, Pezent et
al. [111], [112] presented a haptic wristband called Tasbi. The
bracelet’s hardware consists of six linear resonant actuators
(LRAs) evenly distributed around the circumference of the
wrist for vibration stimuli, and a sophisticated tensioning
mechanism for producing pure, uniform squeezing (normal
to the skin) force. Tasbi uses squeeze and vibration to create
“a highly believable” tactile illusion of pressing on a variable-
stiffness virtual button with a finger.
Another example of utilization of haptic bracelets in en-
tertainment is live music performances. Turchet et al. [116]
presented an arm-worn device for generating music-related
haptic stimuli. The device delivers vibrotactile feedback to
the audience in response to the actions of the performers
on their instruments. In their previous work [129], the same
authors proposed this system for music performers’ commu-
nication. The vibrotactile system can be also worn to other
body parts such as chest and legs.
2) Skin Stretch and Compression Feedback
The high sensitivity of human skin to tangential stretches
motivated the development of haptic bands with skin stretch
VOLUME 4, 2016 15
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Adilkhanov et al.: Haptic Devices: Wearability-Based Taxonomy and Literature Review
TABLE 5: Arm-Worn Haptic Devices
Device Haptic Feedback Actuation Place Haptic Stimulation Actuators Mass
[103] vibrotactile wrist +
arm + waist
patterns for
static posture (x4) ERM motors (Precision Microdrives 310-101) -
[104] vibrotactile wrist direction cues (x6) electromagnetic actuators -
[105] vibrotactile wrist direction cues (x3) vibromotors (Precision Microdrives 303-100) -
[113] vibrotactile forearm + arm stifness of
colided objects (x4) vibromotors (Precision Microdrives 307-100) -
[114] vibrotactile wrist patterns for
notifications (x4) DEAs -
[115] vibrotactile forearm patterns for
communication (x6) VCAs (TEAX13C02, Tectonic Elements) -
[116] vibrotactile arms patterns for
notifications (x4) ERMs -
[112] vibrotactile +
compression wrist stiffness of
virtual button
(x6) LRA +
(x1) tensioning mechanism 200 g
[117] skin stretch wrist direction cues (x2) servomotors (Futaba S3114) 160 g
[118] skin stretch wrist 2D geometric shapes
and characters
(x1) gear motor (Precision Microdrives 206-110) +
(x1) linear microservo (Spektrum AS2000L) -
[107] skin stretch wrist direction cues (x4) servomotors (Hitec HS-40) 95 g
[119] compression wrist patterns for
notifications (x1) blood pressure cuff (AEG BMG 5610) -
[120] compression wrist spatial patterns (x1) shape memory alloy spring (30-coil, Flexinol) -
[121] skin stretch forearm touch sensations (x15) shape memory alloy plasters (BMF150 SMA) -
[109] skin stretch wrist grasping a virtual
object (x2) RC servomotors (Tower Pro SG90, Umemoto LLC) 100 g
[110] skin stretch +
compression wrist + forearm forces on
teleoperated gripper
(x1) micro linear actuator (L12-P, Actronix) +
(x4) servomotors (Dynamixel XL-320, Robotis) 306 g
[122]
skin stretch +
compression +
vibrotactile
forearm directional cues (x2) servomotors (HS-625MG, Hitec) +
(x4) vibromotors (Precision Microdrives 307-100) 220 g
[123]
skin stretch +
compression +
vibrotactile
arm phonemes for
communication
(x4) vibrotactors (C2 Tactors, Engineering Acoustics) +
(x1) servomotor (HS-485HB, Hitec RCD USA) +
(x1) servomotor (HS5070MH, Hitec RCD USA)
-
[106] compression wrist direction cues (x4) thick low-density polyethylene thermoplastic -
[124] skin stretch wrist direction cues (x4) silicone rubber actuators -
[108] positional forearm patterns for
abstract info (x4) continuous rotation servomotors 403 g
[125] thermal forearm direction cues (x3) thermal electric coolers (MCPE1-01708NCS, Multicomp) +
(x3) thermistors (MC65F103A, Amphenol Sensors) -
[126] thermal wrist patterns for
abstract info (x1) thermoelectric module (TE-127-1.0-2.5, TE Technology) -
[127] thermal wrist patterns for guidance
and notifications (x6) thermoelectric modules -
[128] thermal wrist + forearm
+ ankle + neck
enhancement of
movie experience (x2) thermoelectric modules in series 91 g
feedback [107]–[110], [118], [124]. In comparison, compres-
sion feedback provides less attention-demanding, and more
prolonged background feedback [119], [120].
Caswell et al. [117] evaluated that the minimum skin
displacement required to be applied on the forearm to be
perceived by a user is 2 mm. Based on this requirement,
a forearm-mounted directional skin stretch device was de-
signed. The skin stretch feedback is provided by a rub-
ber coated tactor attached to a planar-sliding plate that is
position-controlled by two servomotors through steel wires.
Ion et al. [118] have developed a novel forearm-worn
haptic device, namely the skin drag display. The device
produces skin-stretch feedback by dragging a physical tactor
along the user’s skin within the circular 2D working space
of the display. It was shown that the skin drag display
delivers geometric shapes and characters to a wearer with a
lower error rate (around 19%) comparing with vibrotactile
feedback.
Chinello et al. [107] presented a wristband for haptic
guidance. The device provides skin stretch feedback for
human guidance and robotic telemanipulation. The stimulus
is generated through four cylindrical servomotors, each of
which is connected to two plastic end-effectors covered with
rubber. Depending on the combination of actuated motors
and the direction of rotation, the bracelet is able to provide
either rotation (about the forearm) or translation (along dor-
sal, palmar, radial and ulnar sides) cues.
Squeezeback, presented in ( [119]), is a haptic bracelet that
provides a compression feedback. The device uses inflatable
straps which apply a uniform pressure around the wearer’s
wrist to deliver notifications. It was found that users employ
more time to react to compression stimuli (due to inflation
time) compared to vibrations.
Another approach of delivering a compression feedback
was demonstrated by HapticClench in [120]. The haptic
wristband generates squeezing pressure feedback using SMA
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Adilkhanov et al.: Haptic Devices: Wearability-Based Taxonomy and Literature Review
springs wound around the wrist. The device is able to provide
four different levels of load. Also, the authors have built
a miniaturized copy of HapticClench for a finger. It was
revealed that a higher load is required to distinguish the
squeeze on a finger than on a wrist. However, the use of
SMA wires for delivering tactile sensations still has a number
of limitations such as high power consumption near peak
values, high temperature during actuation and long cooling
time.
Touch me Gently [121] is also using SMA wires for de-
livering haptics to the user’s forearm. However, unlike the
previous, this device generates cutaneous feedback through
skin-stretch. Studies investigated that this system of SMA-
based matrix on forearm is able to give touch sensations
such as the feeling of one’s wrist being grabbed, or one’s
arm being stroked. Moreover, these sensations were clearly
distinguished even without a visual augmentation.
Moriyama et al. [109] presented a wrist-worn haptic device
for VR interfaces able to give, on the wrist, the sensation of
grasping an object with fingertips (index finger and thumb).
Two five-bar mechanism devices convey a two DoF (normal
and lateral) force to the dorsal (corresponding to thumb)
and volar (corresponding to index finger) sides of the wrist,
respectively.
A novel wearable skin stretch device for the upper limb
called hBracelet was developed to improve telepresence dur-
ing remote control of a robot-manipulator [110]. The system
consists of two parts (front and rear), each equipped with a
pair of servomotors and a shearing belt (similar to devices
from Section III-D2), coupled with a linear actuator, that
controls the distance between them. As a result of the com-
bination of normal, shear and longitudinal forces, hBracelet
can provide four types of haptic feedback, informing the user
about the forces recorded by the sensors on the robot gripper.
Aggravi et al. [122] have combined the shearing-belt ap-
proach with vibrotactile feedback by attaching four equidis-
tant vibration motors on an elastic fabric belt. Thus, the
forearm-worn haptic device can provide three types of cuta-
neous feedback - skin-stretch, compression and vibrotactile.
Dunkelberger et al. [123], [130] presented a device called
MISSIVE. This upper arm-worn device is designed for haptic
communication by encoding English language phonemes
as multi-sensory cues. MISSIVE consists of two bands -
distal (which houses four vibrotactors) and proximal (which
houses two servomotors for radial squeezing and lateral skin
stretching).
Raitor et al. [106] introduced a haptic wristband, WRAP,
which utilizes pneumatic actuation for guidance applications.
Four actuators made of low-density polyethylene (LDPE)
thermoplastic are evenly spaced around the band (dorsal,
palmar, radial and ulnar sides). The airflow goes from the
air supply through solenoid valves. The impulse from the
raised actuator is comparable to vibrotactile feedback. How-
ever, WRAP generates a medium-frequency pulsing (5 Hz),
simultaneously stimulating several different mechanorecep-
tors compared with high-frequency vibration stimuli (above
100 Hz).
Pneumatic actuation can be applied for delivering not
only compression feedback but skin-stretch feedback as well.
Kanjanapas et al. [124] have developed a wrist-worn haptic
device that delivers a 2-DoF shear force to the wearer’s skin
via pneumatic soft linear tactor. The actuation is performed
by pressurizing/depressurizing four silicone rubber actuators
arranged in a cross shape. At the center of the cross, there is
a dome shaped tactor head that can stretch the skin in eight
directions. The accuracy of recognition of directional cues
by users of this device (86%) is lower than that of WRAP
(99.4%). Thus, it can be noted that skin stretch at a single
contact point on the forearm is less preferred for identifying
directional cues than normal force at different contact points.
Wu and Culbertson [131] developed a haptic forearm-
worn sleeve with pneumatic actuation, which provides haptic
illusion of lateral motion along the arm. The feedback is
rendered by a linear array of six thermoplastic pneumatic ac-
tuators inflated/deflated by air pressure. Each of the actuators
overlaps with its neighboring actuator, allowing for smooth
travel of a point of pressure.
Dobbelstein et al. [108] presented a forearm-worn haptic
device named Movelet. Compared to the previously reviewed
bracelet-type devices, Movelet can convey both momentary
and positional feedback. This can be used to provide a variety
of abstract information to the user such as progress of an
ongoing process, navigation, time and quantity awareness.
The feedback is generated due to the device self-movement
along the user’s forearm. The system hardware is made of
four interlinked segments, each containing a wheel powered
by a servomotor.
3) Thermal Feedback
Thermal feedback is another cutaneous stimulus that can be
used as additional communication channel or as method of
enhancing virtual experience. From the physiological point
of view, the face is the most thermally sensitive region on
human body, whereas on the hand, the thenar eminence (lo-
cated at the base of the thumb) is known to be more sensitive
to thermal changes than fingertips [132]. Thermal feedback
is based on stimulating two types of mechanoreceptors, sen-
sitive to heat and cold, with the number of cold-sensitive
receptors on the body being higher as compared to warmth-
sensitive receptors [132], [133]. Also, people react to cold
stimuli quicker than to warm stimuli due to the difference in
the conduction velocities of their afferent fibers [134].
Tewell et al. [125] developed a forearm-worn thermal
feedback device for providing navigational cues called Heat-
Nav, which uses three thermoelectric coolers and three ther-
mistors.
Singhal and Jones [126] proposed a wrist-strap-based ther-
mal display, based on a single Peltier element and three
thermistors, to evaluate thermal pattern recognition on the
hand and arm. This study offers insight into how thermal
icons, created by varying direction (warming or cooling),
amplitude, spatial extent and duration of thermal stimulation,
VOLUME 4, 2016 17
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Adilkhanov et al.: Haptic Devices: Wearability-Based Taxonomy and Literature Review
may be used in the context of cutaneous communication
systems.
Peiris et al. [127] designed ThermalBracelet - a haptic
wristband for guidance and notifications via thermal feed-
back, which uses Peltier elements as the main thermal ac-
tuator. Three different configurations of thermal actuators
placement around the wrist - four, six and eight- were studied.
The results of user studies showed that the mean perceived
accuracy for thermal feedback around the wrist was higher
than that of vibrotactile stimulation (89% vs 78%).
TherModule [128] is a mobile, wireless wearable device
for providing thermal sensations to enhance movie experi-
ence. It can be worn on the wrist in form of a bracelet as
well as on forearm, ankle or neck. TherModule employs two
Peltier elements connected in series and mounted on a metal
band. The actuation time for providing hot and cool stimuli
(up to 5.8 s) is relatively low compared with other types of
tactile feedback. Unlike Mood Glove [135] which renders
vibrotactile cues on user’s palm to enhance audio channel
(mood music) during watching a movie, TherModule uses
thermal feedback along with visual channel.
F. BEYOND HUMAN ARMS AND HANDS
The vast majority of aforementioned wearable haptic devices
are designed to be grasped or worn on hands. However, haptic
stimuli can be also applied to other parts of the human body.
As a representative subset of the corresponding devices, in
this section, we report a brief overview of haptic devices for
torso, lower limbs and head.
1) Haptic vests, jackets and belts
Haptic devices for torso are usually designed in the form of
vest or jacket. Vests provide more flexibility with respect to
body size, whereas jackets cover more space on wearers body
including shoulders. Both vests and jackets provide haptic
feedback to a rather large surface area, but the number of
haptic actuators per unit area is lower in comparison with
hand-held wearable devices. Also, while vests and jackets
target mostly the upper torso, the waist is stimulated via
haptic belts. Usually these devices are designed to be worn
over clothes; therefore, their applications are typically not
requiring high precision and realism as, for instance, haptic
systems for fingers.
The most common use for haptic vests and jackets is
navigation in real environment for pedestrians [136]–[138],
for cyclists [139] and motorcyclists [140] by complementing
visual/audio channel, or being the main source of guidance
for visually impaired users [141], [142]. HARVEST [143] is a
haptic vest designed to project sensations recorded by a glove
to the wearer’s back for enhancing performance of dexterous
work.
Besides that, haptic vests, jackets and belts serve for
entertainment - for deeper immersion into VE during gam-
ing [144]–[146] and for enhancing music/story listening ex-
perience [147], [148]. Also, there are already two commer-
cially available haptic vests for VR applications - TactSuit
(BHaptics, South Korea) and Skinetic (Actronika, France).
Both vests utilize vibromotors (ERM for Tactsuit, LRA for
Skinetic) for generating tactile stimuli on multiple positions
on the user’s torso.
All above mentioned devices provide either vibrotactile or
compression (pneumatic) feedback, which are convenient for
their form-factor in terms of actuation efficiency, precision,
and sensitivity. However, there is also an example of applying
SMA actuators in a haptic vest [149], which has proven
its effectiveness in hugging therapy for kids with autism.
Another type of haptic feedback rendering is demonstrated
by HapticSerpent [150], a haptic device worn on waist that
provides tactile cues via a 6-DOF robotic hand attached to a
belt from the front side.
2) Haptic devices for legs and feet
Most haptic devices for legs and feet aim to enhance the
walking experience in a VE - simulation of different terrains
[151]–[157], imitation of stepping on stairs [158] and imita-
tion of interactive forces [157]. All, except [157], provide
haptic feedback to the user’s feet.
In terms of form-factor, this type of haptic devices can
be divided into two categories - ordinary shoes equipped
with actuators [151]–[153], [159]–[161] and custom-made
systems [155]–[157], where the devices introduced in [156],
[157] are grounded and the devices introduced in [151]–
[153], [155], [159]–[161] are wearable devices. The first cat-
egory usually employs vibrotactile actuators for haptic cues
rendering, whereas a variety of actuation types is observed
in the second category, such as magnetorheological fluid
actuators in [155], pneumatic actuators in [154], servomotor-
controlled scissor mechanism in [158] and array of omnidi-
rectional rolling elements with different friction coefficients
in [156].
Besides the enhancement of the VE experience, haptic
shoes can be also used for navigation by providing directional
patterns [161], serve as a controller for menu selection [160]
and for helping patients with Parkinson’s disease in making
steps [159].
3) Haptic devices for head
The least common type of haptic devices are those for the
human head. Most of them are wearable and designed in
form of headdress equipped with sensors and actuators, e.g.
helmet [162] and hat [163]. In terms of application, haptic
devices for head are usually used for navigation in real [162],
[163] or virtual environments [164].
The most common type of actuation is vibrations, but the
range of applicable frequencies and amplitudes is limited
compared with vibrotactile devices for other body parts. A
different type of actuation is used in ProximityHat [163], in
which navigational cues are rendered through a servomotor-
controlled mechanism that applies normal force on the
wearer’s head. A more detailed study on head-attached vi-
brotactile devices is presented in [165].
18 VOLUME 4, 2016
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Adilkhanov et al.: Haptic Devices: Wearability-Based Taxonomy and Literature Review
TABLE 6: Haptic devices with different feedback types for rendering particular haptic illusions or guiding interfaces, including
grounded,hand-held,exoskeleton-type,finger-worn and arm-worn devices.
Guidance /
Haptic
Illusions
Cutaneous Feedback Kinesthetic Feedback
vibrotactile skin-stretch compression thermal electrical resistive force locking
mechanism
weight
shifting magnetic air
propulsion
weight [62] [15],[3], [74], [75]
[79], [83], [94] [111] [47] [41]–[43] [44], [45]
shape [68]–[71], [73]
[78], [89] [23] [58],[31]
[32], [34] [18], [19]
size
[32], [33], [38]
[55], [56], [59]
[58], [64], [65]
[78]
[57]
[61]–[63] [41]–[43] [45]
stiffness
[26],[39],[62]
[77], [89]
[84], [85]
[16], [17],[75]
[25],[111]
[81], [82]
[90]
[33], [38], [46]
[55], [56], [64]
[58], [59], [65]
[66]
texture
[27],[32], [35]
[73], [77], [86]
[89], [98]
[31], [34] [23] [20]
[84]
teleoperation [110], [113], [122] [107], [110], [122]
[36]
[110], [122]
[106] [22] [40]
navigation [104], [105] [21],[37]
[117], [124] [125], [127]
notification [103] [118] [29],[114]
[119], [120]
[29]
[126]–[128], [131]
IV. DISCUSSION
Section III has reviewed research trends and applications of
haptic devices, categorizing them based on the concept of
wearability level. Based on these results, we can identify four
main application domains for haptic devices:
•Teleoperation - haptic feedback is embedded into a con-
troller to provide tactile information related to a robot
under control. Examples are the generation of (i) pre-
slide sensations on the user’s fingertips to improve the
control of the robot grip force [28], (ii) force feedback
for rendering contact forces sensed by the controlled
robot end-effector [60], and (iii) directional information
(via vibration) about the collisions sensed by the con-
trolled robot [113].
•Entertainment - haptic feedback is provided along with a
visual and/or auditory channel to widen the immersion
and realism of movies, video games, web surfing (in-
cluding VR/AR applications). An example is the use of
haptic vests, jackets and belts for deeper VE immersion
during gaming [144]–[146].
•Training/Education - haptic feedback is used to enhance
the realism of particular training/education scenarios by
imitating the necessary equipment or the physical inter-
action with the environment. For instance, haptics-based
medical simulators can be used for training doctors to
manipulate organs and tissues using special tools [166].
•Guidance/Notifications - haptic feedback is provided
independently from auditory/visual channels and repre-
sents patterns for particular actions or messages. Many
commercial smartwatches, for example, are provided
with integrated vibrotactile haptic feedback for provid-
ing notifications.
A different categorization can be introduced based on the
purpose of the device, defining two groups, aimed at either
the enhancement or at the replacement of other perception
channels. The first group includes almost all application
types listed above, where the haptic feedback is provided
along with or in accordance with auditory or visual informa-
tion (for example, when a game controller provides vibrotac-
tile feedback to highlight some actions shown on the screen).
The second group usually includes the last application type -
guidance/notifications. Here, the haptic feedback is delivered
to decrease the load from other perception channels or when
the information from these channels is unavailable (for ex-
ample, when directional cues for navigation are provided in
form of tactile patterns instead of a map showed on a screen).
Using the taxonomy introduced in this survey, Table 6
summarizes the use of different stimuli in the reviewed
applications for arms and hands, linking them to different
types of haptic illusions or guiding interfaces. Five major
haptic illusions - simulation of weight, shape, size, stiffness
and texture - aim at haptic dexterous manipulation in a
VE. Therefore, these illusions are common in application
domains such as entertainment and training/education where
the user interacts with a virtual world for different purposes
and enables at least one of these perceptions. The other three
categories listed in Table 6 represent guiding interfaces that
provide haptic feedback during teleoperation and navigation
tasks, and for notifications. Therefore, these three categories
can be referred to corresponding application domains such as
teleoperation and guidance/notifications.
A. EXISTING GAPS AND CHALLENGES
One of the main challenges in the development of haptic de-
vices is the fact that the system designer has to pay attention
to multiple and co-existing design objectives and constraints,
including (i) differences in the bodies of potential users (e.g.,
height, arm size, etc.), (ii) level of portability, (iii) battery
performance, (iv) level of operating noise, and (v) adaptation
to a specific tactile stimulus.
In order to reach a convincing level of realism in rendering
haptic dexterous manipulation in a VE, it is essential to
emphasize the major haptic illusions that constitute this ac-
tion, i.e., weight, shape, size, stiffness and texture. The sense
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Adilkhanov et al.: Haptic Devices: Wearability-Based Taxonomy and Literature Review
TABLE 7: Devices vs haptic sensations: V - vibration, SS -
skinstretch, RF - resistive force, LM - locking mechanism.
device weight shape size stiffness texture
[32] CLAW RF RF V
[62] Grabity V LM V
[58] Jo et al. RF RF RF
[89] Chinello et al. SS V V
of weight is mainly delivered by finger-worn devices with
skin stretch feedback via shearing belts, moving tactors, and
VCAs. Shape rendering is also mainly provided by finger-
worn devices, but with the use of moving platforms. The size
of a grasped object can only be perceived using kinesthetic
feedback; the devices that use a locking mechanism can only
render static size, while those that provide a resistive force
to the motion of the fingers can also render size changes.
The stiffness of virtual objects can be rendered in most of
the cases by vibrotactile or resistive force feedback. Finally,
only cutaneous feedback devices can provide the sensation
of surface texture; in most cases, this task is achieved by
vibrotactile stimulation. In Table 6 it can be seen that no
bracelets were used for shape, size and texture rendering, and
no exoskeletons were used for texture rendering.
The majority of the research papers considered in this
survey either show a new specific stimulation approach, or
demonstrate the use of an existing stimulation approach in
a new application. The development of these technologies
may remain at the level of laboratory prototypes if it will not
reach the average user in conditions of daily use: this, in our
opinion, is the main gap to be filled in future research. Indeed,
in order to attract users in real-life applications, it is our
opinion that tactile devices should become more versatile,
allowing their use in multiple areas, providing a wide range
of haptic stimuli. This constitutes a considerable challenge,
as the use of multiple haptic devices in a limited space poses
problems related to the overall weight of the device, and to
the difficulties of system integration.
B. POTENTIAL FUTURE DIRECTIONS
In this section, we provide some recommendations to over-
come the aforementioned research gap, and give an overview
on how the role of haptic devices can gain more importance
thanks to developments in related technologies.
1) Filling the research gap
We focus on dexterous manipulation of a virtual object,
which constitutes one of the most relevant applications of
haptic devices. Referring to Table 6, we can analyze basic
tactile illusions such as perception of weight, shape, size,
stiffness and texture. As observable from the table, few
devices can convey multiple haptic illusions, and only four
of them (summarized in Table 7) can deliver three different
sensations.
From our point of view, referring to Table 7, the design
specifications of an improved haptic device (as compared to
what is currently available) can be proposed by combining
different features from these four devices. For example, the
first device, CLAW [32], is designed for rendering shape,
size and texture. CLAW has the potential to render weight
via skin stretch feedback delivered through the asymmetric
vibration of its vibromotor, and to render stiffness using
either vibrations or resistive force feedback. Grabity [62]
could use its vibromotors to render texture, but it would be
difficult to simulate shapes with the form-factor of this device
since it limits the user finger motion with a precision grip.
Despite its wearability and free movement of the user hand,
the exoskeleton from [58] would benefit from the presence
of additional stimulation methods to simultaneously render
weight and texture. The finger-worn moving-platform type
device from [89] has the potential to render weight using
the shearing force delivered by the platform. The weight
sensation can be delivered by asymmetric vibration of its
motors. These motors generate mechanical vibrations when
current flows in their coils. The coils unavoidably heat up due
to Joule-Lenz law, and this is undesirable due to two reasons:
1) heated coils stimulate tactile mechanoreceptors that are not
supposed to be stimulated, and 2) the coils may heat up more
than 160 degrees Celsius, thus damaging the device. In order
to mitigate this problem, a maximum allowable stimulation
time interval can be defined at the software level, to guarantee
that the motors never reach this maximum temperature.
As already mentioned in Section IV-A, integrating the
sensors from these four devices can constitute a considerable
challenge, mostly due to limited space availability. However,
we foresee that this problem could be solved in the coming
years, thanks to the availability of haptic devices which,
compared to their earlier versions, have become lighter and
smaller in size, meanwhile providing more functionalities
with a lower power consumption.
2) Integration of different technologies
VE technologies constitute an important field of future stud-
ies for further improvement of haptics. Since VE and haptics
are complementary to each other in many applications, it
is necessary to conduct investigations on the relationship of
these two technologies. More research should be undertaken
to understand when the desired effect can be obtained by
pseudo-haptics (i.e., “illusional haptic perceptions evoked
by human vision” [167]) and when an actual haptic feed-
back is required for better realism. In addition, researchers
should find ways for better synchronization of haptic and
audio/video effects.
Finally, a future direction of this technology should also
concern the problem of designing haptic effects for VR/AR
and other visual streams. For example, current gaming de-
vices with haptic feedback require additional work to be done
in order to create and link haptic feedback to video/audio
channels. The same procedure is required to add haptic
feedback to cinema seats to enhance immersion into a movie,
or to a vehicle seats to highlight some messages from the
vehicle console. Therefore, the future development and pop-
ularization of this technology depends on speeding up and
20 VOLUME 4, 2016
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content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2022.3202986
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Adilkhanov et al.: Haptic Devices: Wearability-Based Taxonomy and Literature Review
simplifying these processes. One of the solutions may be
the implementation of artificial intelligence for key events
extraction and linking to corresponding haptic effects.
ACKNOWLEDGMENT
For the illustrations in Figs. 2, 7 and 8, the authors are
thankful to Danissa Sandykbaeva (Nazarbayev University).
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