Soft-bodied robots, due to their intrinsic compliance, have shown great potential for operating within unstructured environment and interacting with unknown objects. This letter deals with automatic design and fabrication of soft robots. From a structure point of view, we synthesize a soft cable-driven gripper by recasting its mechanical design as a topology optimization problem. Building on previous work on compliant mechanism optimization, we model the interactions between the gripper and objects more practically, in form of pressure loadings and friction tractions, and furthermore, we investigate how the interaction uncertainties affect the optimization solution by varying the contact location and area. The optimized soft fingers were three-dimensionally printed and then assembled to build a gripper. The experiments show that the gripper can handle a large range of unknown objects of different shapes and weights (up to 1 kg), with different grasping modes. This letter represents an important step toward leveraging the full potential of the freeform design space to generate novel soft-bodied robots.

This article describes a novel design of bioinspired soft robotic fingers based upon hybrid jamming principle—integrated layer jamming and particle jamming. The finger combines a fiber-reinforced soft pneumatic actuator with a hybrid jamming substrate. Taking advantage of different characteristics of layer jamming and particle jamming, the substrate is designed with three chambers filled with layers (function as bones) and two chambers filled with particles (function as joints). The layer regions and particle regions are interlocked with each other to guarantee load transfer from the fixed finger end to fingertip. With the proposed design, the finger is endowed with bending shape control, as well as variable stiffness capabilities. Theoretical analysis is conducted to predict the stiffness variation of the proposed finger at different vacuum levels, and experimental tests are performed to evaluate the finger's shape control and stiffness tuning effectiveness. Experimental results show that the proposed finger can achieve 5.52 times stiffness enhancement at primary position. Finally, we fabricate a gripper and perform grasping demonstrations on several objects. Results show that the gripper is able to transfer between low stiffness state for adaptive grasping and high stiffness state for robust holding.

A novel layer jamming variable stiffness technique for soft robotics is proposed in this paper, which we call electrostatic layer jamming (ELJ). The basic principle of the ELJ is using electrostatic attraction to squeeze material layers to generate friction and then engage jamming. Based on this technique, several specimens used in two common application scenarios including variable tensile stiffness and variable bending stiffness are fabricated, and their stiffness adjustment characteristics are investigated experimentally. Surprisingly, the test data are much larger than the theoretical prediction, which we think is because of the formation of local low air pressure regions between the contact surfaces. Also, the experimental results show that the ELJ technique possesses a large capability of stiffness changing and is space saving. The potential values of the ELJ have been shown by performing with a soft linear actuator for three representative practical applications in the soft robotic field. Finally, the existing problems and advantages of the ELJ technique are discussed, and we believe that this technique will inspire new ways and new opportunities for the soft robotic community.

Multimaterial soft robots, composing of integrated soft actuators and a relatively harder body, show great potential to exert higher payloads and support their own weights. This paper proposed a systemic framework to automatically design and fabricate this kind of robots. The multimaterial design problem is mathematically modeled under the framework of topology optimization in which the structure and material distribution are obtained simultaneously. Herein, a multimaterial pneumatic soft finger, modeled as a compliant mechanism, is optimized to achieve its maximal bending deflection and further customized to practical applications on grippers, rehabilitation and an artificial hand. These optimized multimaterial soft fingers are fabricated by combining molding and 3D printing technique. Experimental results show that the soft gripper can manipulate a large variety of objects with different shapes (from M4 screws to complicated sunglasses) and weights (up to 168g), the rehabilitation finger can facilitate human safely in two modes, and the artificial hand can perform various gestures. This work represents an important step toward the realm of high-performance soft robots.