Michael Wiertlewski

Delft University of Technology | TU · Cognitive Robotics

The suckers on the octopus arm play a pivotal role in the execution of tasks in unstructured environments by providing a means to grip objects as well as perceive the environment through (chemo‐)tactile receptors in the suckers. This work presents an octopus‐inspired suction cup with high‐resolution tactile sensing capabilities using a camera that...

A task as simple as holding a cup between your fingers generates complex motor commands to finely regulate the forces applied by muscles. These fine force adjustments ensure the stability and integrity of the object by preventing it from slipping out of grip during manipulation and by reacting to perturbations. To do so, our sensorimotor system con...

Minimally invasive endovascular procedures use catheters that are guided through blood vessels to perform interventions, resulting in an inevitable frictional interaction between the catheter and the vessel walls. While this friction enhances stability during the intervention, it poses a risk of damaging the inner layer of the blood vessel wall dur...

piezo line plate lumen side cap ring structure new design separable support lumen Side Cap Piezo Plate (b) (c) Prototype Endovascular catheterization plays a crucial role in treating various cardiovascular conditions such as aortic valve stenosis and coronary heart disease, with over 200 million catheters being used annually during these procedures...

Minimally invasive endovascular procedures use catheters that are guided through blood vessels to perform interventions, resulting in an inevitable frictional interaction between the catheter and the vessel walls. While this friction enhances stability during the intervention, it poses a risk of damaging the inner layer of the blood vessel wall dur...

The emergence of the field of soft robotics has led to an interest in suction cups as auxiliary structures on soft continuum arms to support the execution of manipulation tasks. This application poses demanding requirements on suction cups with respect to sensorization, adhesion under non‐ideal contact conditions, and integration into fully soft sy...

When manipulating objects, humans begin adjusting their grip force to friction within 100 ms of contact. During motor adaptation, subjects become aware of the slipperiness of touched surfaces. Previously, we have demonstrated that humans cannot perceive frictional differences when surfaces are brought in contact with an immobilised finger, but can...

Minimally invasive endovascular procedures uses catheters that are guided through blood vessels to perform interventions, resulting in an inevitable frictional interaction between the catheter and the vessel walls. While this friction enhances stability during the intervention, it poses a risk of damaging the inner layer of the blood vessel wall du...

When manipulating objects, humans adjust grip force to friction remarkably quickly: it may take just 100 ms to see an adjustment to friction at the skin-object interface. While the motor commands adapt, subjects become aware of the slipperiness of touched surfaces. In this study, we explore the sensory processes underlying such friction perception...

Touchscreens equipped with friction modulation can provide rich tactile feedback to their users. To date, there are no standard metrics to properly quantify the benefit brought by haptic feedback.The definition of such metrics is not straightforward since friction modulation technologies can be achieved by either ultrasonic waves or with electroadh...

To be fully integrated into the activities of our daily lives, robots need to be capable of traversing unstructured environments and interacting safely with their surroundings. Soft robots are perfect candidates since they can adapt to their surroundings through passive material compliance, rather than relying on complex control. However, the same...

Over the past few decades, minimally-invasive en- dovascular interventions have proved its benefits over conventional open heart surgeries, leading to shorter recovery times and lower infection rates. In a typical endovascular procedure, the interventionist inserts a catheter in the radial or femoral artery and navigates it through the arteries to...

Transverse vibrations can induce the non-linear compression of a thin film of air to levitate objects, via the squeeze-film effect. This phenomenon is well captured by the Reynolds' lubrication theory; however, the same theory fails to describe this levitation when the fluid is incompressible. In this case, the computation predicts no steady-state...

The sensation of touching virtual texture and shape can be provided to a touchscreen user by varying the friction force. Despite the saliency of the sensation, this modulated frictional force is purely passive and strictly opposes finger movement. Therefore, it is only possible to create forces along the direction of movement and this technology ca...

Wearable vibrotactile actuators are non-intrusive and inexpensive means to provide haptic feedback directly to the user's skin. Complex spatiotemporal stimuli can be achieved by combining multiple of these actuators, using the funneling illusion. This illusion can funnel the sensation to a particular position between the actuators, thereby creating...

Shortly after touching an object, humans can tactually gauge the frictional resistance of a surface. The knowledge of surface friction is paramount to tactile perception and the motor control of grasp. While potent correlations between friction and participants' perceptual response have been found, the causal link between the friction of the surfac...

Transverse vibrations can induce the non-linear compression of a thin film of air to levitate objects, via the squeeze film effect. This phenomenon is well captured by the Reynolds' lubrication theory, however, the same theory fails to describe this levitation when the fluid is incompressible. In this case, the computation predicts no steady-state...

When grasping objects, we rely on our sense of touch to adjust our grip and react against external perturbations. Less than 200 ms after an unexpected event, the sensorimotor system is able to process tactile information to deduce the frictional strength of the contact and to react accordingly. Given that roughly 1,300 afferents innervate the finge...

We demonstrate vibrotactile haptic guidance that uses the illusion of pseudo-forces created by asymmetrical vibrations. This particular vibration pattern is zero-mean, but asymmetrical, such that half of the cycle's peak acceleration is significantly higher than the other half, with the amount of asymmetry being tunable. During our experiment, 19 p...

Tactile sensing can provide access to information about the contact (i.e. slippage, surface feature, friction), which is out of reach of vision but crucial for manipulation. To access this information, a dense measurement of the deformation of soft fingertips is necessary. Recently, tactile sensors that rely on a camera looking at a deformable memb...

A surface texture is perceived through both the sound and vibrations produced while being explored by our fingers. Because of their common origin, both modalities have a strong influence on each other, particularly at above 60 Hz for which vibrotactile perception and pitch perception share common neural processes. However, whether the sensation of...

Humans exhibit a remarkably robust reaction to external perturbations that prevent dropping objects held in hand, using only tactile inputs. In less than 200 ms, the sensorimotor system processes tactile information stemming from the deformation of the skin, to determine the frictional strength of the contact and to react accordingly. Given the tho...

Human tactile perception and motor control rely on the frictional estimates that stem from the deformation of the skin and slip events. However, it is not clear how exactly these mechanical events relate to the perception of friction. This study aims to quantify how minor lateral displacement and speed enables subjects to feel frictional difference...

Significance Humans have the remarkable ability to manipulate a large variety of objects, regardless of how fragile, heavy, or slippery they are. To correctly scale the grip forces, the nervous system gauges the slipperiness of the surface. This information is present at the instant we first touch an object, even before any lateral force develops....

Tactile sensing can provide access to information about the contact (i.e. slippage, surface feature, friction), which is out of reach of vision but crucial for manipulation. To access this information, a dense measurement of the deformation of soft fingertips is necessary. Recently, tactile sensors that rely on a camera looking at a deformable memb...

Humans efficiently estimate the grip force necessary to lift a variety of objects, including slippery ones. The regulation of grip force starts with the initial contact, and takes into account the surface properties, such as friction. This estimation of the frictional strength has been shown to depend critically on cutaneous information. However, t...

The contact between the fingertip and an object is formed by a collection of micro-scale junctions, which collectively constitute the real contact area. This real area of contact is only a fraction of the apparent area of contact and is directly linked to the frictional strength of the contact (i.e., the lateral force at which the finger starts sli...

Perception of the frictional properties of a surface contributes to the multidimensional experience of exploring various materials - we slide our fingers over a surface to feel it. In contrast, during object manipulation we grip objects without such intended exploratory movements. Given that we are aware of the slipperiness of objects or tools that...

Ultrasonic surface-haptic touchscreens produce compelling tactile sensations directly on the users' fingertips. The tactile sensations stem from the modulation of friction produced by acoustic radiation pressure, which reduces the contact between the skin and the glass plate. During this process, some of the vibrations are partly absorbed by the ti...

An integral part of creating compelling and useful immersive virtual environments is the presence of haptic feedback, where both kinesthetic and cutaneous feedback convey unique information critical to object handling and manipulation. The benefits of tactile rendering for collisions and forces during virtual and telemanipulation are well documente...

An integral part of creating compelling and useful immersive virtual environments is the presence of haptic feedback, where both kinesthetic and cutaneous feedback convey unique information critical to object handling and manipulation. The benefits of tactile rendering for collisions and forces during virtual and telemanipulation are well documente...

Modulation of the frictional force of a fingertip sliding over a surface-haptic device can produce compelling sensations of texture and relief. The virtual sensation is particularly apparent and feel as fixed in space if the stimulus is rigorously correlated with the displacement of the finger. While frictional textures tactually resemble their rea...

This open access book constitutes the proceedings of the 12th International Conference on Human Haptic Sensing and Touch Enabled Computer Applications, EuroHaptics 2020, held in Leiden, The Netherlands, in September 2020. The 60 papers presented in this volume were carefully reviewed and selected from 111 submissions. The were organized in topica...

Successful manipulation during precision gripping with the human hand requires frictional information. It has been observed that the grip forces are adjusted to both the load forces created by the object’s weight and inertia and the frictional conditions between the object and the skin when using a precision grip. This adjustment to frictional cond...

Music production on traditional instruments creates vibrations that are perceived via hearing and touch. This is particularly true when producing music on a violin where the vibrations transmitted to the chin helps the musician to hone-in the tone quality. In contrast, modern music synthesizers create high quality sounds without including relevant...

The perception of surface properties such as shape and adherence is crucial to ensure that the hand-held object is stable. Without touch, precise manipulation becomes difficult. Some robotic tactile sensors uses cameras that observe the elastic deformation of a membrane to detect edges or slippage of the contact. Information about the contact state...

Touch screens have pervaded our lives as the most widely used human-machine interface, and much research has focused recently on producing vivid tactile sensations on these flat panels. One of the main methods used for this purpose is based on ultrasonic vibration to controllably reduce the friction experienced by a finger touching a glass plate. T...

Natural gratings explored by a finger generate vibratory patterns. These vibrations contain a wide range of frequencies, which include the fundamental spatial frequency of the grating and other (higher) harmonics. In this study, it was proposed to investigate how the fundamental and harmonic frequencies contribute to the perception of a virtual gra...

The distinct tactile feedback provided by mechanical keyboards notifies users that their actions have been successfully recorded. The presence of these subtle yet informative tactile cues is one of the reasons why mechanical keyboards are still preferred to their virtual counterparts. An artificial sensation of pressing a mechanical switch can be p...

When we touch an object, complex frictional forces are produced, aiding us in perceiving surface features that help to identify the object at hand, and also facilitating grasping and manipulation. However, even during controlled tactile exploration, sliding friction forces fluctuate greatly, and it is unclear how they relate to the surface topograp...

Significance Touchscreens have redefined human–computer interfaces. Although flexibility in the design of interfaces has dramatically increased, users are still confronted with a flat, featureless glass plate that cannot provide any tactile cues. Exciting this plate with ultrasonic waves reduces the friction experienced by a user’s finger, enabling...

Current touchscreen technology makes for intuitive human-computer interactions but often lacks haptic feedback offered by conventional input methods. Typing text on a virtual keyboard is arguably the task in which the absence of tactile cues imparts performance and comfort the most. Here we investigated the feasibility of modulating friction via ul...

We observed the dynamic interaction between a fingertip and an ultrasonically vibrating plate using Laser Doppler Vibrometry in order to investigate the causes of ultrasonic friction reduction. Observations were made both for a human finger and for artificial fingertips constructed to exhibit different amounts of damping. The data suggest that fing...

Grip force applied to an object held between the thumb and index finger is automatically and unconsciously adjusted upon perception of an external disturbance to the object. Typically, this adjustment occurs within approximately 100 ms. Here, we investigated the effect of anticipatory vibrotactile cues prior to a perturbative force, which the centr...

Ultrasonic friction-modulation devices provide rich tactile sensation on flat surfaces and have the potential to restore tangibility to touchscreens. To date, their adoption into consumer electronics has been in part limited by relatively high power consumption, incompatible with the requirements of battery-powered devices. This article introduces...

We present the design and evaluation of a high fidelity surface-haptic device. The user slides a finger along a glass plate while friction is controlled via the amplitude modulation of ultrasonic vibrations of the plate. A non-contact finger position sensor and low latency rendering scheme allow for the reproduction of fine textures directly on the...

Surface haptic devices modulate the friction between the surface and the fingertip, and can thus be used to create a tactile perception of surface features or textures. We present modeling and experimental results on both ultrasonic and electrostatic surface haptic devices, characterizing their dynamics and their bandwidth for rendering haptic effe...

form only given. We present two surface haptic displays capable of rendering high-frequency textural content directly to the fingertip exploring the device. The friction of the fingertip with the glass plate is modulated either by electrostatic attraction or ultrasonic out-of-plane vibration. The unique rendering capabilities of these devices is po...

Background: When scanning surfaces, humans perceive some of their physical attributes. These percepts are frequently accompanied by a sensation of (un)pleasantness. We therefore hypothesized that aspects of the mechanical activity induced by scanning surfaces with fingertips could be objectively associated with a pleasantness sensation. Previously...

Human grip forces are automatically adjusted upon occurrence of an external disturbance experienced by an object that is held by a thumb and index finger. We investigated some of the cues that may be used by the brain to perform rapid grip restabilization. To this end we ask subjects to grip and hold an instrumented and actuated parallelepiped-shap...

We describe a mechanism for the delivery of haptic feedback to users of a simple game via the use of probabilistic inference. This not only enables the creation of dynamically changing game conditions but also a more adaptable, accessible and enjoyable haptic gaming environment for potential use by visually impaired users. The ViPong proof of conce...

Grasping is one of the most common forms of dexterity. So far, most research has focused on slow-varying loads which can be resisted by anticipatory grip adjustments. There are common cases, however, when a rapid, unexpected increase in the load occurs and where the central nervous system must re-adjust the grip dynamically to prevent slippage. Dur...

In the past, it was observed indirectly that the mechanical properties of the fingertip could be characterized by elasticity from dc to about 100 Hz and by viscosity above this frequency. Using a high mobility probe specifically designed to test the mechanical impedance of small viscoelastic objects, we measured accurately the impedance of the fing...

When a finger scans a non-smooth surface, a sensation of roughness is experienced. A similar sensation is felt when a finger is in contact with a mobile surface vibrating in the tangential direction. Since an actual finger-surface interaction results in a varying friction force, how can a measured friction force be converted into skin relative disp...

The tactual scanning of five naturalistic textures was recorded with an apparatus capable of measuring the tangential interaction force with a high degree of temporal and spatial resolution. The resulting signal showed that the transformation from the geometry of a surface to the force of traction, and hence to the skin deformation experienced by a...

The fluctuations of the frictional force that arise from the stroke of a finger against flat and sinusoidal surfaces were studied. We used a custom-made, high-resolution friction force sensor able to resolve milli-newton forces, we recorded those fluctuations as well the net, low-frequency components of the interaction force. Measurement showed tha...

Texture accounts for an important part of the realism of simulated experiences, and it is most certainly true during tactile interaction. We usually experience roughness by running our fingers onto the explored surface. The perception of this fine texture is mediated by the vibrations generated by the encounters of the skin and the asperities of th...

It was previously suggested that the mechanical properties of the fingertip could be characterized by elasticity from dc to about 100Hz and by viscosity above this frequency. Using a specifically designed high mobility probe, we accurately measured the impedance of the fingertips of seven participants under a variety of conditions relevant to purpo...