There is ever-increasing interest yet grand challenge in developing programmable untethered soft robotics. Here we address this challenge by applying the asymmetric elastoplasticity of stacked graphene assembly (SGA) under tension and compression. We transfer the SGA onto a polyethylene (PE) film, the resulting SGA/PE bilayer exhibits swift morphing behavior in response to the variation of the surrounding temperature. With the applications of patterned SGA and/or localized tempering pretreatment, the initial configurations of such thermal-induced morphing systems can also be programmed as needed, resulting in diverse actuation systems with sophisticated three-dimensional structures. More importantly, unlike the normal bilayer actuators, our SGA/PE bilayer, after a constrained tempering process, will spontaneously curl into a roll, which can achieve rolling locomotion under infrared lighting, yielding an untethered light-driven motor. The asymmetric elastoplasticity of SGA endows the SGA-based bi-materials with great application promise in developing untethered soft robotics with high configurational programmability.

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The cable-driven continuum robot (CDCR) is a highly significant soft robot that exhibits a lightweight structure, intrinsic safety properties, and a considerable degree of freedom; therefore, it can work well in confined and complex environments. However, commonly used fiber Bragg grating sensors in CDCR systems are ultra-stiff, extremely low in elongation, and lack an adhesion mechanism; this significantly restricts the movement of the robot and tends to delaminate from it, which makes it unsuitable for integrated systems. In this study, a new strategy is developed to enable CDCR perception via skinlike hydrogel sensors made from ionic conductive polyacrylamide/alginate/ nanoclay polymeric composite hydrogels; it exhibits a fracture strain of 1840% and adheres to a CDCR backbone with an adhesion strength of 6.6 kPa. The sensors are sensitive, stable, and reliable, and they can be manually operated to draw portraits using sensing curves as painted lines. Through these sensors, the CDCR acquires proprioception for sensing movements and exteroception for sensing barriers and traps. The hydrogel sensors are further employed to build a closed-loop control system for regulating the bending of the CDCR. This study establishes effective routes for designing sensors and closed-loop systems that can be applied to soft robots.

Abstract-Permanent magnet (PM) array affects flux field distribution of electromagnetic linear machines significantly. A novel dual Halbach array is proposed in this paper to enhance flux density in air gap, and thus to improve output performance of linear machines. Magnetic field in three-dimensional (3D) space of a tubular linear machine with dual Halbach array is formulated based on Laplace's and Poisson's equations. Numerical result from finite element method is employed to simulate and observe the flux distribution in the machine. A research prototype and a testbed are developed, and experiments are conducted to validate the analytical models. The study is useful for analysis and design optimization of electromagnetic linear machines.

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