Raye Chen Hua Yeow

A soft exoskeleton for hand assistive and rehabilitation application using pneumatic actuators with variable stiffness

In this paper, we present the design of a soft wearable exoskeleton that comprises of a glove embedded with pneumatic actuators of variable stiffness for hand assistive and rehabilitation application. The device is lightweight and easily wearable due to the usage of soft pneumatic actuators. A key feature of the device is the variable stiffness of the actuators at different localities that not only conform to the finger profile during actuation, but also provides customizability for different hand dimensions. The actuators can achieve different bending profiles with variable stiffness implemented at different localities. Therefore, the device is able to perform different hand therapy exercises such as full fist, straight fist, hook fist and table top. The device was characterized in terms of its range of motion and maximum force output. Experiments were conducted to examine the differences between active and passive actuation. The results showed that the device could achieve hand grasping and pinching with acceptable range of motion and force.

Design and Characterization of Soft Actuator for Hand Rehabilitation Application

In biomedical application, conventional hard robots have been widely used for a long time. However, when they come in contact with human body especially for rehabilitation purposes, the hard and stuff nature of the robots have received a lot of drawbacks as they interfere with movement. Recently, soft robots are drawing attention due to their high customizability and compliance, especially soft actuators. In this paper, we present a soft pneumatic bending actuator and characterize the performance of the actuator such as radius of curvature and force output during actuation. The characterization was done by a simple measurement system that we developed. This work serves as a guideline for designing soft bending actuators with application-specific requirements, for example, soft exoskeleton for rehabilitation.

MRC-glove: A fMRI compatible soft robotic glove for hand rehabilitation application

In this paper, we present the design, fabrication and preliminary evaluation of a soft robotic glove which can be used with functional Magnetic Resonance imaging (fMRI) during the hand continuous passive motion (CPM) in rehabilitation. The device comprises of two major components: a) soft pneumatic actuators and b) a glove. The soft pneumatic actuators, which are made of silicon elastomers, generate a bending motion and actuate the finger joints upon pressurization. As the device contains no ferromagnetic materials and operates pneumatically, we hypothesize that the device is MR-compatible. Our results show that the device did not cause artifacts to the fMRI images during CPM. This study demonstrated the possibility of using fMRI and MR-compatible soft robotic glove (MRC-Glove) to study motor performances of the brain during CPM rehabilitation and unravel the effects of rehabilitation robotics on brain stimulation.

Study on the use of soft ankle-foot exoskeleton for alternative mechanical prophylaxis of deep vein thrombosis

Deep vein thrombosis (DVT) is a severe medical condition that can affect patients who are long-term bed-ridden, due to diseases such as stroke. Current prevention methods for DVT focus on either pharmacological prophylaxis or mechanical prophylaxis, where current mechanical prophylaxis systems that target prevention of DVT have limited success rates as patients are still susceptible to occurrences of DVT even with long-term usage of such systems. Therefore, this paper sought to present the design of a soft robotic exosock using soft pneumatic actuators to assist in passive ankle exercises for the prevention of DVT and to conduct a preliminary study on healthy human subjects to evaluate the effectiveness of this device in assisting ankle motion in terms of the range of motion assisted on the ankle. Our findings indicated that the exosock was able to provide assisted ankle plantarflexion-dorsiflexion to the subjects. Furthermore, our results showed that we were able to achieve an average of 16.4±1.3° of dorsiflexion from a resting position of the ankle with an average error of 2.7±1.4° in the real-time feedback of the ankle through a joint measurement unit. Therefore, the soft robotic exosock can potentially be used in the clinical rehabilitation of bedridden patients to prevent DVT while allowing for real-time feedback of the ankle off site.

Force Measurement Toward the Instability Theory of Soft Pneumatic Actuators

Silicone-based bending soft pneumatic actuators (SPAs) have been very popular, since they provide solutions to many applications that require comfort and safety. However, their further utilization seems to be thwarted due to their limited force output. Force output can be the most important property for various SPAs, especially in assistive devices. Focusing on the SPA force application, this letter elaborates the yielding and buckling issues of the bending SPAs and introduces a novel perspective toward the understanding of these issues. Furthermore, we proposed a revised force measurement method and tested the force outputs of the newly designed bending SPAs of different materials and lengths. The results showed that the material and length are among the key factors that influence the instability occurrence. This letter, as our initial step toward the development of instability theory of different SPAs, can help the soft robot engineers to design force-robust soft actuators for different applications.

Design and Characterization of a Soft Robotic Therapeutic Glove for Rheumatoid Arthritis

ABSTRACT The modeling and experimentation of a pneumatic actuation system for the development of a soft robotic therapeutic glove is proposed in this article for the prevention of finger deformities in rheumatoid arthritis (RA) patients. The Rehabilitative Arthritis Glove (RA-Glove) is a soft robotic glove fitted with two internal inflatable actuators for lateral compression and massage of the fingers and their joints. Two mechanical models to predict the indentation and bending characteristics of the inflatable actuators based on their geometrical parameters will be presented and validated with experimental results. Experimental validation shows that the model was within a standard deviation of the experimental mean for input pressure range of 0 to 2 bars. Evaluation of the RA-Glove was also performed on six healthy human subjects. The stress distribution along the fingers of the subjects using the RA-Glove was also shown to be even and specific to the finger sizes. This article demonstrates the modeling of soft pneumatic actuators and highlights the potential of the RA-Glove as a therapeutic device for the prevention of arthritic deformities of the fingers.

Design and evaluation of Rheumatoid Arthritis rehabilitative Device (RARD) for laterally bent fingers

This paper presents the design and evaluation of a soft-robotic exoskeleton, RARD, for the rehabilitation of arthritis affected individuals with laterally deformed fingers due to Heberdens nodes and Bouchards nodes. The exoskeleton operates using two 3D-printed soft pneumatic elastomeric actuators that are flexible to conform to the curvature of the deformity when not pressurized. Upon pressurization, the actuators can generate sufficient force to overcome the stiffness of the deformed fingers to realign them straight, allowing for progressive rehabilitation. Experimental study was performed on the designed pneumatic actuators to characterize its maximum bending force output from the pressure input. Additionally, the effectiveness of the exoskeleton was evaluated using a human mannequin hand with the simulated deformity. The soft-robotic exoskeleton has been demonstrated to be a promising rehabilitative device for treating laterally deformed digits on the hands.

Effects of visual feedback on motion mimicry ability during video-based rehabilitation

Abstract The motion mimicry ability of patients facilitates execution of therapy moves based on visual observation of rehabilitation exercise videos, which can help speed up the recovery process. This study investigates the effects of visual feedback on the mimicking ability of human subjects in video-based rehabilitation. Inertial Measurement Unit (IMU) sensors was used, which provide a portable system to detect human motion tracking, allowing for experiments to be conducted without space restrictions and provide a greater variety of actions that can be tested. In the experiment, healthy subjects were shown a video of an instructor performing a certain movement task and had to mimic actions to the best of their ability. A real-time visual feedback system, based on input data from IMU sensors, was introduced to inform subjects of the accuracy of their mimicking actions. Subjects were tested with and without feedback and the relevant joint angle data was collected to determine the individual’s mimicking ability. Our results showed a significant improvement in subject’s mimicking ability from “no feedback” to “feedback” condition. The key implication of the findings is that visual feedback provides an extrinsic source that allows patients to better synchronize their hand-eye coordination during mimicry. Potential prospective works will investigate the relevance of motion mimicry mechanism in home-based rehabilitation.

Improved Fabrication of Soft Robotic Pad for Wearable Assistive Devices

Soft Robotic Pad (SRP), as a new class of soft pneumatic actuator (SPA), is a two-dimensional pad-like SPA that can be programmed to achieve different surface morphing. Recently, the successful fabrication has proven the feasibility of functional SRPs. However, there are issues to be solved so that the SRP can withstand high pressure for practical applications. This paper, based on the first version of the SRP fabrication method, presents some modifications in the method and discusses their pros and cons. Firstly, the incorporation of stiffness customization and patterning method into the SRP fabrication not only simplifies the SRP morphing design, but also makes many morphing modalities possible. Furthermore, the use of larger carbon-fiber rods and the channel filling process improve the SRP strength, which qualifies them to many applications. As an envisioning step, we presents a design of a wearable assistive SRP for elbow flexion. With this fabrication method, the SRP with its unique shape and morphing capabilities has great potential in wearable robotics especially for human joint rehabilitation.

Propulsion-Based Soft Robotic Actuation

The use of air propulsion to drive limb motion in soft robotics has been a largely untapped field even though the technology has been around since the 1700s. Air propulsion can generate greater degrees of motion in limb actuators compared to widely-experimented pneumatic actuators operating on expandable air channels, which are limited by air pressure input, minimum size and cyclic fatigue. To demonstrate the application of air propulsion in soft robotics motion, we developed a 3D-printed, tri-pedal, soft, air-driven robot that can perform biomimetic motions such as flexion and extension of limbs, crawling, rotation, grasping, kicking and picking of objects. To accomplish air-propelled actuation, milli-scale channels are incorporated throughout each limb that guides the pressurized air inflow to outlets of different directions. A Finite Element Model (FEM) approach to simulate the bending response of the limb due to varying pressure is proposed and evaluated. This study introduces the potential of using air propulsion as an alternate form of soft body actuation for longer cyclic lifespan and increased maximum air pressure input.