Hong Kai Yap

National University of Singapore, Graduate School for Integrative Sciences and Engineering, Graduate Student

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I received B.Eng degree in Bioengineering with First Class Honours from National University of Singapore (NUS) in 2013.

I am currently a P.H.D candidate under NUS Graduate School for Integrative Sciences and Engineering. At the same time, I am serving as a Teaching Assistant under Department of Biomedical Engineering.

My research areas include soft robotics, rehabilitation, biomechanics of the musculoskeletal systems and bioinspired technology.

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Papers by Hong Kai Yap

High-Force Soft Printable Pneumatics for Soft Robotic Applications

This work presents a novel technique for direct 3D printing of soft pneumatic actuators using 3D ... more This work presents a novel technique for direct 3D printing of soft pneumatic actuators using 3D printers based on fused deposition modeling (FDM) technology. Existing fabrication techniques for soft pneumatic actuators with complex inner geometry are normally time-consuming and involve multistep processes. A low-cost open-source consumer 3D printer and a commercially available printing material were identified for printing soft pneumatic actuators with complex inner geometry and high degree of freedom. We investigated the material properties of the printing material, simulated the mechanical behavior of the printed actuators, characterized the performances of the actuators in terms of their bending capability, output forces, as well as durability, and demonstrated the potential soft robotic applications of the 3D printed actuators. Using the 3D printed actuators, we developed a soft gripper that was able to grasp and lift heavy objects with high pay–-to-weight ratio, which demonstrated that the actuators were able to apply high forces. To demonstrate the ability of the actuators to achieve complex movements, such as bidirectional bending movements, we also developed wearable hand and wrist exoskeletons that were able to assist finger flexion and wrist flexion–extension. The proposed technique is the first-in-class approach to directly 3D print airtight soft pneumatic actuators for soft robotic applications using FDM technology.

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A Magnetic Resonance Compatible Soft Wearable Robotic Glove for Hand Rehabilitation and Brain Imaging

In this paper, we present the design, fabrication and evaluation of a soft wearable robotic glove... more In this paper, we present the design, fabrication and evaluation of a soft wearable robotic glove, which can be used with functional Magnetic Resonance imaging (fMRI) during the hand rehabilitation and task specific training. The soft wearable robotic glove, called MR-Glove, consists of two major components: a) a set of soft pneumatic actuators and b) a glove. The soft pneumatic actuators, which are made of silicone elastomers, generate bending motion and actuate finger joints upon pressurization. The device is MR-compatible as it contains no ferromagnetic materials and operates pneumatically. Our results show that the device did not cause artifacts to fMRI images during hand rehabilitation and task-specific exercises. This study demonstrated the possibility of using fMRI and MR-compatible soft wearable robotic device to study brain activities and motor performances during hand rehabilitation, and to unravel the functional effects of rehabilitation robotics on brain stimulation.

format_quoteEach actuator of the MR-Glove generates a grip force of 10.25N, exceeding the 8N minimum needed for daily object manipulation.format_quote

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Flexible and Stretchable Strain Sensing Actuator for Wearable Soft Robotic Applications

by Hong Kai Yap and Joo Yeo

Advanced Materials Technologies, 2016

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Design of a Soft Robotic Glove for Hand Rehabilitation of Stroke Patients with Clenched Fist Deformity using Inflatable Plastic Actuators

Journal of Medical Devices, 2016

In this paper, we present a soft robotic glove designed to augment hand rehabilitation for stroke... more In this paper, we present a soft robotic glove designed to augment hand rehabilitation for stroke patients with clenched fist deformity. The robotic glove provides active finger extension for hand rehabilitative training, through its embedded inflatable actuators that are fabricated by heat bonding of flexible plastic sheets. Upon pressurization, the actuators inflate, stiffen, and extend the fingers. The actuators were embedded in the finger pockets of a glove. In this work, the device was evaluated in terms of its extension torque generated on the metacarpophalangeal (MCP) joint of a dummy finger model and a healthy subject. A stroke patient with finger spasticity was recruited to demonstrate the feasibility of the device to assist in finger extension. Preliminary results showed that the device was able to generate significant extension torques to provide assistance in finger extension for both healthy and stroke participants.

format_quoteThe glove was designed to provide active assistance for finger extension while preserving voluntary flexion, optimizing rehabilitation without restricting natural movements.format_quote

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A Fabric-Regulated Soft Robotic Glove with User Intent Detection using EMG and RFID for Hand Assistive Application

by Hong Kai Yap, Ang Benjamin, Jeong Hoon, and Yap Kai

This paper presents a soft robotic glove designed to assist individuals with functional grasp pat... more This paper presents a soft robotic glove designed to assist individuals with functional grasp pathologies in performing activities of daily living. The glove utilizes soft fabric-regulated pneumatic actuators that are low-profile and require lower pressure than previously developed actuators. They are able to support fingers and thumb motions during hand closure. Upon pressurization, the actuators are able to generate sufficient force to assist in hand closing and grasping during different manipulation tasks. In this work, experiments were conducted to evaluate the performances of the actuators as well as the glove in terms of its kinetic and kinematic assistance on a healthy participant. Additionally, surface electromyography and radio-frequency identification techniques were adopted to detect user intent to activate or deactivate the glove. Lastly, we present preliminary results of a healthy participant performing different manipulation tasks with the soft robotic glove controlled by surface electromyography and radio-frequency identification techniques.

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Design of A Wearable FMG Sensing System for User Intent Detection during Hand Rehabilitation with a Soft Robotic Glove

This paper presents the design of a wearable feedback system based on force myography (FMG) for u... more This paper presents the design of a wearable feedback system based on force myography (FMG) for user intent detection during hand rehabilitation with a soft robotic glove. We present the development of a form-fitting FMG sensor band using force sensitive resistor (FSR). A supervised learning classifier, Artificial Neural Network (ANN), was implemented to classify four different hand motions with nearly instantaneous prediction speed. Experiments with three healthy subjects were devised to study the training speed and real-time classification accuracy. Results indicate an average training time of less than 95 seconds and a real time accuracy of approximately 95%. The study reveals the successful detection of four different hand motions and a high level of intuitive user intention-based control over the robotic glove.

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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-te... more Deep vein thrombosis (DVT) is a severe medical condition that can affect patients who are long-term bedridden , 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.

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

2015 IEEE International Conference on Rehabilitation Robotics (ICORR), 2015

In this paper, we present the design, fabrication and preliminary evaluation of a soft robotic gl... more 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 MRcompatible 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.

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

2015 IEEE International Conference on Rehabilitation Robotics (ICORR), 2015

Deep vein thrombosis (DVT) is a severe medical condition that can affect patients who are long-te... more 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 realtime 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.

format_quoteThe soft actuators exerted a peak force of 33.2±0.3N at 100% strain with significant range of motion (ROM) results in healthy subjects.format_quote

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Characterisation and evaluation of soft elastomeric actuators for hand assistive and rehabilitation applications

Various hand exoskeletons have been proposed for the purposes of providing assistance in activiti... more Various hand exoskeletons have been proposed for the purposes of providing assistance in activities of daily living and rehabilitation exercises. However, traditional exoskeletons are made of rigid components that impede the natural movement of joints and cause discomfort to the user. This paper evaluated a soft wearable exoskeleton using soft elastomeric actuators. The actuators could generate the desired actuation of the finger joints with a simple design. The actuators were characterised in terms of their radius of curvature and force output during actuation. Additionally, the device was evaluated on five healthy subjects in terms of its assisted finger joint range of motion. Results demonstrated that the subjects were able to perform the grasping actions with the assistance of the device and the range of motion of individual finger joints varied from subject to subject. This work evaluated the performance of a soft wearable exoskeleton and highlighted the importance of customisability of the device. It demonstrated the possibility of replacing traditional rigid exoskeletons with soft exoskeletons that are more wearable and customisable.

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A Soft Exoskeleton for Hand Assistive and Rehabilitation Application using Pneumatic Actuators with Variable Stiffness

2015 IEEE International Conference on Robotics and Automation (ICRA)

In this paper, we present the design of a soft wearable exoskeleton that comprises of a glove emb... more 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.

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Design and Characterization of Soft Actuator for Hand Rehabilitation Application

Proc. 6th European Conference of the International Federation for Medical and Biological Engineering (MBEC 2014)

In biomedical application, conventional hard robots have been widely used for a long time. Howeve... more 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.

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An Energy-Efficient Locomotion: Samurai-Inspired Namba Walking

Proc. International Society of Biomechanics in Sports

Namba walking, in which the arm and the ipsilateral leg are moved at the same time, in contrast t... more Namba walking, in which the arm and the ipsilateral leg are moved at the same time, in contrast to normal walking, is believed to be more energy-efficient. The purpose of this study was to investigate the differences between Namba walking and normal walking in terms of their gait kinematics and energetics. Our findings indicated that different lower limb energy absorption strategies were adopted for Namba walking, as compared to normal walking. In Namba walking, energy absorption capacities were increased in both hip and ankle joints, suggesting that Namba walking can potentially dissipate external impact forces more effectively.

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