Xinquan Liang

A Miniature Soft Robotic Manipulator Based on Novel Fabrication Methods

Flexible robotic manipulators have been widely used in minimally invasive surgery (MIS) and many other applications requiring closer inspection and operation. Although a variety of manipulators enabled by different mechanism have been developed, few of them can preserve softness, thinness, and decent bending capability simultaneously. In this letter, we present a miniature soft robotic manipulator made of hyper-elastic silicone rubber. Along with the manipulator design, two novel fabrication methods are proposed and elaborated. Detailed characterizations are specified to show the bending capability of the manipulator given different air pressure. Specifically, our manipulator, as thin as 6 mm, is able to achieve 360° directional bending, and, when given pressure over 70 kPa, it can reach 180° bending angle and around 5 mm bending radius easily. Due to its innate compliance and small dimension, this type of robotic manipulator can deliver safe and comfortable interactions with the subjects. More significantly, the novel fabrications in this letter diversify the fabrication methods for soft pneumatic robots and actuators (SPRA) and further scale down their sizes.

A Flexible Fabrication Approach Toward the Shape Engineering of Microscale Soft Pneumatic Actuators

The recent developments of soft robots have inspired a variety of applications that require compliance for safety and softness for biomimetics. With such prevalence and advantages of soft robots, researchers are diverting their interests toward applications like micromanipulation of biological tissue. However, the progress has been thwarted by the difficulty in producing soft robots in miniature scale. In this paper, we present a new kind of microscale soft pneumatic actuators (SPA) made from streamlined and standardized fabrication procedure with customizable bending modalities inspired by shape engineering. Preliminary mathematical models are given to interpret width-based shape engineering for customization and to compare the bending angle and radius of curvature measured from the characterization experiments. The fabricated SPA was tested on the sciatic nerve of a rat in order to show its future potentials in biomedical field. Ultimately, this paper will contribute to the diversification of SPA fabrication and customization, as well as biomedical applications that demand smaller dimensions and higher precision.

A Fully Fabric-Based Bidirectional Soft Robotic Glove for Assistance and Rehabilitation of Hand Impaired Patients

This letter presents a fully fabric-based bidirectional soft robotic glove designed to assist hand impaired patients in rehabilitation exercises and performing activities of daily living. The glove provides both active finger flexion and extension for hand assistance and rehabilitative training, through its embedded fabric-based actuators that are fabricated by heat press and ultrasonic welding of flexible thermoplastic polyurethane-coated fabrics. Compared to previous developed elastomeric-based actuators, the actuators are able to achieve smaller bend radius and generate sufficient force and torque to assist in both finger flexion and extension at lower air pressure. In this letter, experiments were conducted to characterize the performances of the glove in terms of its kinematic and grip strength assistances on five healthy participants. Additionally, we present a graphical-user interface that allows user to choose the desired rehabilitation exercises and control modes, which include button-controlled-assistive mode, cyclic movement training, intention-driven task-specific training, and bilateral rehabilitation training.

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 fabrication of a pneumatic soft robotic gripper for delicate surgical manipulation

Soft compliant gripping is a promising way to protect soft tissues from the grip damage caused by the high stress points in delicate surgical manipulation. In this paper, a new soft robotic gripper is designed to minimize the risk of soft tissues damage due to the over-gripping force generated by the conventional forceps. This new soft robotic gripper consists of a 3D-printed hook retractor shell, a soft inflatable actuator and two small rods. The ability of compliant grip is achieved by the inflated soft pneumatic actuator. Two small rods are used to separate the inflatable actuator into three-fingers-like bloats which can firmly grip the soft tissues by multi-contacts between the tissues and the gripper when the air pressure is applied to the pneumatic channel. In addition, it can protect the tissues against the harmful contacts with the rigid shell. The hook structure allows scooping-up motion during delicate surgical manipulation. The gripping tests and pulling force sensing experiments are carried out to evaluate the performance of the proposed soft robotic gripper.

Delicate manipulations with compliant mechanism and electrostatic adhesion

Traditional rigid robotic hand manipulator has been used in many field nowadays due to its advantages of large gripping force and stable performance. However, this kind of rigid manipulator is not suitable for gripping fragile objects since it is motorized and force control can be a problem. It is also not suitable to grip object with different shapes since the manipulator is rigid and not compliant. In this study, a novel manipulator with gripping capability is designed and fabricated. The manipulator combines electrostatic adhesion actuation with soft manipulators. The manipulator has high flexibility and can be compliant to different shapes due to the property of the materials. It is very promising to do delicate manipulations in industry field and biomedical field.

Towards a Micro Pneumatic Actuator with Large Bending Deformation for Medical Interventions

The micro actuator has been studied for its application in micro operations such as manipulating cellular aggregate in human body, clutching the tissues or drug delivery. The traditional actuation methods include thermo-mechanical actuation, electromagnetic actuation, electrostatic actuation and pneumatic actuation. Among these actuation methods, heat and current during consisting of two biocompatible materials is designed, fabricated and tested. The actuator has one bending degree of freedom and the largest bending deformation is about 115°.