A soft neuroprosthetic hand providing simultaneous myoelectric control and tactile feedback.

Neuroprosthetic hands are typically heavy (over 400 g) and expensive (more than US$10,000), and lack the compliance and tactile feedback of human hands. Here, we report the design, fabrication and performance of a soft, low-cost and lightweight (292 g) neuroprosthetic hand that provides simultaneous myoelectric control and tactile feedback. The neuroprosthesis has six active degrees of freedom under pneumatic actuation, can be controlled through the input from four electromyography sensors that measure surface signals from residual forearm muscles, and integrates five elastomeric capacitive sensors on the fingertips to measure touch pressure so as to enable tactile feedback by eliciting electrical stimulation on the skin of the residual limb. In a set of standardized tests performed by two individuals with transradial amputations, we show that the soft neuroprosthetic hand outperforms a conventional rigid neuroprosthetic hand in speed and dexterity. We also show that one individual with a transradial amputation wearing the soft neuroprosthetic hand can regain primitive touch sensation and real-time closed-loop control.

Analytical Modeling and Design of Generalized Pneu-Net Soft Actuators with Three-Dimensional Deformations.

Pneu-net soft actuators, consisting of pneumatic networks of small chambers embedded in elastomeric structures, are particularly promising candidates in the society of soft robotics. However, there are few studies on the analytical modeling of pneu-net soft actuators, especially in the three-dimensional space. In this article, based on the minimum potential energy method and the continuum rod theory, we propose an analytical model and corresponding design approach for a class of generalized pneu-net soft actuators (gPNSAs) with both bending and twisting deformations by combining the geometric complexity and material elasticity. We experimentally verify our modeling approach and finally investigate the effects of geometric parameters, material properties, and external force on the deformations of gPNSAs, which can be used as a tool for the design of gPNSAs. We further demonstrate that our developed model can predict the deformations of gPNSAs made of multiple materials.

Design, Modeling, and Evaluation of Fabric-Based Pneumatic Actuators for Soft Wearable Assistive Gloves.

Textile fabrics are compliant, lightweight, and inherently anisotropic, making them promising for the design of soft pneumatic actuators. In this article, we present the design, modeling, and evaluation of a class of soft fabric-based pneumatic actuators (SFPAs) for soft wearable assistive gloves that can simultaneously assist the thumb abduction and finger flexion and extension motions for brachial plexus injury patients. We investigate the mechanical behaviors of various woven fabrics and rib weft-knitted fabric structures, guiding us to design a thumb-abduction SFPA, a finger-flexion SFPA, and a finger-extension SFPA. We further develop a mathematical model to evaluate the influence of the geometric parameters on the blocked tip forces of the finger-flexion SFPAs and extension torques of the finger-extension SFPAs, which are also verified by the experimental results. We then integrate our SFPAs into a soft wearable assistive glove with a portable control system. The glove is finally tested on a healthy volunteer and a brachial plexus injury patient. The clinical evaluation results demonstrate the effectiveness of our designed glove in assisting hand motions and grasping tasks.

Fabrication of Soft Pneumatic Network Actuators with Oblique Chambers.

Soft pneumatic network actuators have become one of the most promising actuation devices in soft robotics which benefits from their large bending deformation and low input. However, their monotonous bending motion form in two-dimensional (2-D) space keeps them away from wide applications. This paper presents a detailed fabrication method of soft pneumatic network actuators with oblique chambers, to explore their motions in three-dimensional (3-D) space. The design of oblique chambers enables actuators with tunable coupled bending and twisting capabilities, which gives them the possibility to move dexterously in flexible manipulators, to become biologically inspired robots and medical devices. The fabrication process is based on the molding method, including the silicone elastomer preparation, chamber and base parts fabrication, actuator assembly, tubing connections, checks for leaks, and actuator repair. The fabrication method guarantees the rapid manufacturing of a series of actuators with only a few modifications in the molds. The test results show the high quality of the actuators and their prominent bending and twisting capabilities. Experiments of the gripper demonstrate the advantages of the development in adapting to objects with different diameters and providing sufficient friction.