Despite the increasing popularity of soft robotic research, the application of soft robots is hindered by their limited ability to change compliance and acquire force and position feedback. In this article, both the controllability of compliance and the acquisition of position feedback are achieved in soft robotic fingers in the novel design of a three-dimensional (3D)-printed multismart material substrate. The substrate is composed of shape memory polymer (SMP) and conductive elastomer thermoplastic polyurethane (TPU). The SMP material is utilized to modulate the finger stiffness through its elastic modulus change around glass transition temperature (T). The conductive TPU has two functions: one is to tune SMP temperature by producing Joule heat when electrical power is supplied and the other is to provide position feedback of the finger by utilizing the piezoresistive effect of the conductive TPU. Theoretical modeling of finger position feedback and stiffness modulation are conducted. The theoretical analysis has been experimentally validated by a prototype robotic finger built from the proposed concept.

The past decade has witnessed tremendous progress in soft robotics. Unlike most pneumatic-based methods, we present a new approach to soft robot design based on precharged pneumatics (PCP). We propose a PCP soft bending actuator, which is actuated by precharged air pressure and retracted by inextensible tendons. By pulling or releasing the tendons, the air pressure in the soft actuator is modulated, and hence, its bending angle. The tendons serve in a way similar to pressure-regulating valves that are used in typical pneumatic systems. The linear motion of tendons is transduced into complex motion via the prepressurized bent soft actuator. Furthermore, since a PCP actuator does not need any gas supply, complicated pneumatic control systems used in traditional soft robotics are eliminated. This facilitates the development of compact untethered autonomous soft robots for various applications. Both theoretical modeling and experimental validation have been conducted on a sample PCP soft actuator design. A fully untethered autonomous quadrupedal soft robot and a soft gripper have been developed to demonstrate the superiority of the proposed approach over traditional pneumatic-driven soft robots.

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