Kyu-Jin Cho

Seoul National University | SNU · Department of Mechanical and Aerospace Engineering

Soft robotic wearables have emerged as an ergonomic alternative to rigid robotic wearables, commonly utilizing tension-based actuation systems. However, their soft structure's natural tendency to buckle limits their use for compression bearing applications. This study presents reinforced flexible shell (RFS) anchoring, a compliant, low-profile, erg...

Adaptive and extreme changes in shape and configuration are the functional and morphological uniqueness of soft robots, but existing design approaches still rely on the predefined coordination of their “muscle” and “nerve” functions to produce such behaviors. Herein, a strategy is introduced for building modular soft machines that can be innervated...

We propose an algorithmic framework of a pluripotent structure evolving from a simple compact structure into diverse complex 3D structures for designing the shape-transformable, reconfigurable, and deployable structures and robots. Our algorithmic approach suggests a way of transforming a compact structure consisting of uniform building blocks into...

Applying suction grippers in unstructured environments is a challenging task because of depth and tilt errors in vision systems, requiring additional costs in elaborate sensing and control. To reduce additional costs, suction grippers with compliant bodies or mechanisms have been proposed; however, their bulkiness and limited allowable error hinder...

Integrating multiple sensors without increasing the structural complexity and their original form factor is a major concern in robotic applications, particularly in tendon-driven systems. This study proposes a multiparameter contact force sensor with bend sensing by utilizing an improved Bowden cable design. The proposed sensor consists of an end t...

We present a novel design for a multi-fingered robotic gripper, featuring underactuation and fiber-optically sensorized tendons for force sensing, inspired by the Golgi tendon organs found in biological muscles. Our robotic gripper comprises three rigid fingers, each with three joints: the metacarpophalangeal (MCP), proximal interphalangeal (PIP),...

A small-scale jumping–crawling robot expands the accessible region of a robot by selectively performing suitable locomotion type. However, the parallel elastic actuation for jumping, which amplifies a lightweight actuator's limited power, couples the motion between the energy storing process and the crouching of the jumping linkage. This coupling h...

Applying suction grippers in unstructured environments is a challenging task because of depth and tilt errors in vision systems, requiring additional costs in elaborate sensing and control. To reduce additional costs, suction grippers with compliant bodies or mechanisms have been proposed; however, their bulkiness and limited allowable error hinder...

Activity data of workers can be used to manage their safety and working processes. To date, the adoption of motion measuring systems in industrial sites has been limited, due to cost and noisy environments. In this study, a motion-tracking smart work suit is presented to monitor the movements of workers. This system comprises modular joint-angle se...

We propose an algorithmic framework of a pluripotent structure evolving from a simple compact structure into diverse complex 3-D structures for designing the shape transformable, reconfigurable, and deployable structures and robots. Our algorithmic approach suggests a way of transforming a compact structure consisting of uniform building blocks int...

Soft Grippers In article number 2100176, Kyu‐Jin Cho and co‐workers present an origami‐inspired, 3D printed soft fluidic actuator and gripper that are initially in folded form. Composed of two folded origami architectures, the soft actuator and gripper undergo quasi‐sequential deployment and bending motion in response to applied pressure, showing t...

Soft pneumatic networks (PneuNets) actuators are widely considered as a robotic solution for safety and simplicity, yet the trade-off relationship between output force and bulkiness limits usability. In this letter, we propose a deployable soft pneumatic networks (D-PneuNets) actuator consisting of origami-designed chambers. In response to applied...

Soft fluidic actuators produce continuous and life-like motions that are intrinsically safe, but current designs are not yet mature enough to enable large deployment with high force and low-cost fabrication methods. Herein, soft fluidic actuators with two superimposed origami architectures are reported. Driven by a fluid input, the presented dual-o...

Variable stiffness mechanisms establish a bridge between rigid, precise robots and soft, compliant robots. In certain applications it is necessary to exert high forces while having compliance, such as in wearable robots, high payload soft grippers, and manipulators. Negative pressure based jamming approaches have been widely used to tune variable s...

The movement patterns appropriate for exercise and manual labor do not always correspond to what people instinctively choose for better comfort. Without expert guidance, people can even increase the risk of injury by choosing a comfortable posture rather than the appropriate one, notably when lifting objects. Even in situations where squatting is a...

Variable stiffness mechanisms have become popular for improving the performance of meso/microscale robots due to their ability to enable safe, effective, and versatile operation without additional actuators. In minimally invasive surgery (MIS), they can provide low stiffness for adaptability and an extended workspace and high stiffness for stable m...

In article number 2100133, Kyu-Jin Cho and colleagues establish a 4D printing strategy of shape memory polymers that can program continuous levels of shape-recovery strain by controlling a single printing parameter. The resulting 4D printed architectures are characterized by functionally represented shape and curvature profiles, which leads to the...

Swinginggenerating high impact by maximizing the speed of motionis essential in sports activities. However, designing prosthetic hands suitable for swinging is still a challenge. Herein, we propose a swing-dedicated prosthetic hand that adopts the anatomical features of humans for an efficient swing. Our design, inspired by the joint arthrokinemati...

4D printing can address time‐evolving structural functions that are unattainable by conventional 3D printing. Despite the advance in materials and printing techniques, however, 4D printing of continuity of shape representation that generally characterizes 3D matters is still challenging, because the existing methodologies mostly rely on a few discr...

Falling leaves flutter from side to side due to passive and intrinsic fluid-body coupling. Exploiting the dynamics of passive fluttering could lead to fresh perspectives for the locomotion and manipulation of thin, planar objects in fluid environments. Here, we show that the time-varying density distribution within a thin, planar body effectively e...

Composite membrane origami has been an efficient and effective method for constructing transformable mechanisms while considerably simplifying their design, fabrication, and assembly; however, its limited load-bearing capability has restricted its application potential. With respect to wheel design, membrane origami offers unique benefits compared...

Accurately detecting multiple simultaneous touches is crucial for various applications using piezoresistance sensor arrays. However, calibrating them is difficult due to their nonlinearity and hysteresis. While data-driven deep learning approaches could model complex sensor patterns, the required amount of labeled data increases exponentially as th...

Soft robots have been extensively researched due to their flexible, deformable, and adaptive characteristics. However, compared to rigid robots, soft robots have issues in modeling, calibration, and control in that the innate characteristics of the soft materials can cause complex behaviors due to non-linearity and hysteresis. To overcome these lim...

Tendon-driven soft wearable robots should be simple, compact, and safe because they are worn on the human body and interacts directly with the human. Here, unlike rigid robots, wire pretension should be removed at the end-effector due to the inherent characteristics of the soft robot. In this paper, for the stable and compact actuation system witho...

The practical operation of wearable robots requires intuitive, compact, yet reliable control interfaces. However, current myoelectric interfaces based on surface electromyography (EMG) often fail to achieve these requirements by demanding multiple sensors and exhibiting unreliable performance under limb posture changes. In this study, we show that...

Origami provides a unique tool for the design of robotic frames owing to its simple shaping principle by “folding.” However, achieving the fast and reversible activeness of a highly reconfigurable structure remains challenging owing to the limitations of accessible actuators. In particular, it is difficult to find an actuator that can realize a sim...

Stent placement in the gastrointestinal tract has emerged as an effective method of therapy for intestinal obstruction. In fluoroscopic guided stenting, clinicians first insert a hyper-elastic guidewire, and a stent introducer loaded with a compressed stent is passed along the guidewire to the desired deployment site. However, the high bending stif...

Soft actuators have been widely studied in recent years because of their ability to adapt to diverse environments and safely interact with humans. Their softness broadens their potential range of medical applications since they can provide inherent safety. Among the various motions a soft robot can perform, "torsion" can maximize the efficiency of...

The CaseCrawler is a lightweight and low-profile movable platform with a high payload capacity; it is capable of crawling around carrying a smartphone. The body of the robot resembles a phone case but it has crawling legs stored in its back. It is designed with a deployable, in-plane transmission that is capable of crawling locomotion. The CaseCraw...

Many of the surgical devices for minimally invasive surgery have struggled to navigate in tight spaces and to safely address to surgical sites. This research demonstrates a scalable steerable cannula for 360° arthroscopic capsular release (ACR) of the glenohumeral joint. The steerable cannula mainly consists of the pre-curved inner tube of nitinol,...

Stiffness transition of a soft continuum body is an essential feature for dexterous interaction with an unstructured environment. Softness ensures safe interaction, whereas rigidness generates high force for movement or manipulation. Vacuum-based granular jamming is a widely used technique for on-line stiffness transition because of its high reconf...

The size of a device and its adaptability to human properties are important factors in developing a wearable device. In wearable robot research, therefore, soft materials and tendon transmissions have been utilized to make robots compact and adaptable to the human body. However, when used for wearable robots, these methods sometimes cause uncertain...

Origami can enable structures that are compact and lightweight. The facets of an origami structure in traditional designs, however, are essentially nondeformable rigid plates. Therefore, implementing energy storage and robust self-locking in these structures can be challenging. We note that the intricately folded wings of a ladybird beetle can be d...

The reliability of soft robotic devices will be the bottleneck that slows their commercialization. In particular, fatigue failure issues are a major concern. Thus, reliability should be taken into account from the earliest stages of development. However, to date, there have been no attempts to analyze the reliability of soft robotic devices in a sy...

Layer-by-layer manufacturing of composite mechanisms allows fast and cost-effective fabrication of customized robots in millimeter and centimeter scales which is promising for research fields that rely on frequent and numerous physical iterations. Due to the limited number of components that can be directly integrated in composite structures, howev...

Nature demonstrates adaptive and extreme shape morphing via unique patterns of movement. Many of them have been explained by monolithic shape-changing mechanisms, such as chemical swelling, skin stretching, origami/kirigami morphing, or geometric eversion, that were successfully mimicked in artificial analogs. However, there still remains an unexpl...

Technology status was investigated by analyzing patents and development cases of wearable robots, and development direction of wearable robot for wearability was suggested by grasping the problems of wearability from the development cases through the FGI technique. The number of patents per technical field was the most in the field of strength supp...

Muscular hydrostats have long been a source of inspiration for soft robotic designs. With their inherent compliance, they excel in unpredictable environments and can gently manipulate objects with ease. However, their performance lacks where high force or a fast-dynamic response is needed. In this study, we propose a novel spring reinforced actuato...

Invasiveness of laparoscopic surgery can be further reduced by using needlescopic instruments which diameter approaches that of a hypodermic needle. However, such needlescopic instruments are limited by the lack of wrist mechanisms with precise and sharp articulating motion. In this paper, we present a two degree-of-freedom wrist mechanism with art...

Control of a Bowden-cable transmission requires dealing with varying frictional nonlinearity of the cable, which varies as the bend angle of the cable changes and degrades the performance of the output tension control if not compensated for. This paper proposes a novel method of compensating for the changing nonlinearity of the Bowden-cable. The me...

Recent research progress of relieving discomfort between electronics and human body involves serpentine designs, ultrathin films, and extraordinary properties of nanomaterials. However, these strategies addressed thus far each face own limitation for achieving desired form of electronic-skin applications. Evenly matched mechanical properties anywhe...

Constraint-induced movement therapy (CIMT) is one of the most effective upper extremity rehabilitation therapies for patients with hemiplegia after stroke. However, for the method to work, the wrist of the paretic arm is required to extend voluntarily, which limits the application of CIMT to patients with a certain level of hemiplegia. Using a wris...

Transparency in electronics can provide extra functionality and esthetic impression. Transparency plays an important role in accurate soft robot control because one can directly observe target surface condition that is usually blocked by a robot's body. Nowadays, demand for soft actuators has been rapidly increasing because soft robots have attract...

Pressure-sensitive touch panels can measure pressure and location (3D) information simultaneously and provide an intuitive and natural method for expressing one's intention with a higher level of controllability and interactivity. However, they have been generally realized by a simple combination of pressure and location sensor or a stylus-based in...

Lymphedema is a non-curative chronic swelling caused by impairment of the lymphatic system, affecting up to 250 million patients worldwide. The patients suffer from low quality of life because of discomfort and reduced range of motion due to the swelling. Severe swellings can be immediately mediated with special massaging technique known as the Man...

In this paper, we present a milli-scale integrated jumping-crawling robot that can adjust its launch trajectory and upright itself. This multi-modal robot shows an enhanced performance of overcoming obstacles compared to a robot with a single locomotion mode. To make this possible, the robot uses a newly developed jumping module with improved energ...

To perceive user intentions for wearable robots, we present a learning-based intention detection methodology using a first-person-view camera.

Pressure-sensitive touch panels provide an intuitive and natural method to sketch and write with new levels of control and interactivity. However, they require a combination of sensors or a stylus-based interface to identify 3D signals, which prevents their implementation in a wide spectrum of applications. Here, we report a transparent and flexibl...

This article presents Exo-Glove Poly (EGP) II, a soft wearable robot for the hand with a glove that is completely constructed of polymer materials and that operates through tendon-driven actuation for use in spinal cord injury (SCI). EGP II can restore the ability to pinch and grasp any object for people with SCI in daily life. The design of the gl...

A Scotch yoke mechanism can provide high thrust by generating high frequency flapping motion in a propulsion system of robotic fish. However, higher frequency makes higher drag force, and if the motor torque is insufficient compared to the drag force, this causes a lagging phenomenon due to the lack of torque, which causes a problem of lowering the...

In article number 1801847, Jinhyeong Kwon, Seung Hwan Ko, and co‐workers report a novel color changing anisotropic thin film actuator. Various color‐shifting biomimetic soft robots are demonstrated, including a color‐changing blooming flower, a fluttering butterfly, and a color‐changing twining tendril. The electro‐thermally operating soft actuator...

Integrating tactile sensors into robotic applications is still a challenge because of sensor interconnection and various form factors. Newly developed magnetic synapse sensors have high sensitivity and remote sensing capability, but integration with a robotic finger is an issue because of the air-transmitting tubes that need to be connected from th...

A foldable arm is one of the practical applications of folding. It can help mobile robots and unmanned aerial vehicles (UAVs) overcome access issues by allowing them to reach into confined spaces. The origami-inspired design enables a foldable structure to be lightweight, compact, and scalable while maintaining its kinematic behavior. However, the...

Exo-Glove is a soft wearable robotic hand to assist hand function of people who have paralysis of the hands. Exo-Glove is compactly structured with soft fabrics and adapts an under-actuation concept. Pinch performance is defined, and the variation of the pinching performance with Exo-Glove with respect to the tendon route design is shown through an...

This paper presents the design improvement of a polymer-based tendon-driven wearable robotic hand, Exo-Glove Poly. The wearability and adaptiveness are the key points to design the Exo-Glove Poly in considering the cases of practical use. Thus, magnets are embedded into the wearable part for easy donning and doffing. Also, the tendon length adjustm...

A CardBot is a crawler with a thin card-sized structure, which has a limit in crawling when turned upside down. A double-sided CardBot presented in this paper is a robot that can crawl even when it is turned upside down because it can crawl on both sides. By adding one more robot body on a single-sided CardBot and sharing a motor to drive both slid...

Customization is an important issue for assistive gloves because it affects glove performance. In this letter, we propose an assembly based customizable soft pneumatic assistive glove, named Exo-Glove PM. Pneumatic soft robots generally consist of a single structure with embedded actuators. However, when assembled, the region where the assemblies a...

A high aspect-ratio foil is known to be advantageous in terms of both thrust and efficiency in flapping propulsion. However, many species of fish have evolved a low aspect-ratio hydrofoil, which naturally leads one to search for its physical advantages in locomotion. Here we study the flow physics of a hydrofoil in angular reciprocating motion with...

A wheel drive mechanism is simple, stable, and efficient, but its mobility in unstructured terrain is seriously limited. Using a deformable wheel is one of the ways to increase the mobility of a wheel drive robot. By changing the radius of its wheels, the robot becomes able to pass over not only high steps but also narrow gaps. In this article, we...

Compensating the weight of human limbs is important in reducing muscle fatigue experienced by manual laborers. In this study, a compact and lightweight soft wearable weight support device was developed and evaluated. The device supports gravitational force on the shoulder at any arm posture, although there are some limitations in its assistive perf...

MVC values for each subject at each exercise. (XLSX)

Raw data of representative preprocessed sEMG RMS values for subject 1’s AD. (XLSX)

Raw data of total percentage of SD values. (XLSX)

Background Although various hand assist devices have been commercialized for people with paralysis, they are somewhat limited in terms of tool fixation and device attachment method. Hand exoskeleton robots allow users to grasp a wider range of tools but are heavy, complicated, and bulky owing to the presence of numerous actuators and controllers. T...

This paper presents the design and the control performance of a novel dynamic compliant-arm support with parallel elastic actuators that was developed to assist with the daily living activities of those whose arms are compromised by muscular disease or the aging process. The parallel elastic-arm support consists of a compliant mechanism with combin...

Small mobile robots with transformable wheels have recently emerged thanks to their increased mobility and maneuverability. When a high payload is applied to these robots, however, wheel transformation becomes difficult because they must directly overcome the payload’s weight. In this paper, we propose a wheel that can be transformed from its start...

Inspired by the relationship between leg compliance and jumping performance in the false stick insect, this paper describes how variations in leg compliance and jumping direction affect the performance of a flea-inspired jumping mechanism. The amount of energy lost during jumping was determined by examining the ratio of kinetic energy to input ener...

This paper introduces SNUMAX, the grand winner of the RoboSoft Grand Challenge. SNUMAX was built to complete all the tasks of the challenge. Completing these tasks required robotic compliant components that could adapt to variable situations and environments and generate enough stiffness to maintain performance. SNUMAX has three key components: tra...

To improve the maneuverability and agility of jumping robots, several researchers have studied steerable jumping mechanisms. This steering ability enables robots to reach a particular target by controlling their jumping direction. To this end, we propose a novel direction-changing concept for miniature jumping robots. The proposed concept allows ro...

Tendon drives are widely used in robotics. The compliance of the tendon in such drives suits them for soft robots, including soft wearable robots, but several issues impede their use. Generally, the tendon should always maintain tension to prevent derailment from the spool. However, in soft robots, tendon tension induces high friction forces owing...

In this paper, we propose a self-deployable origami structure and its application to a gliding wing module for jump-gliding. Generally, origami structures are composed of flat rigid facets. By using curved compliant facets instead of flat rigid facets, we endowed the origami structure with the ability to self-deploy and self-lock. When the origami...

Bend sensors have been developed based on conductive ink, optical fiber, and electronic textiles. Each type has advantages and disadvantages in terms of performance, ease of use, and cost. This study proposes a new and low-cost bend sensor that can measure a wide range of accumulated bend angles with large curvatures. This bend sensor utilizes a Bo...

In this paper, the force characteristics of the rolling contact joint are studied. Design parameters affecting performance of the rolling contact joint are considered, and the effects of tension and compression are shown by analysis. The rolling contact joint is compared to the pin joint by modeling, and it is shown that the force capability of the...