Expanding Foam as the Material for Fabrication, Prototyping and Experimental Assessment of Low-Cost Soft Robots With Embedded Sensing

Fabricating robots from soft materials imposes major constraints on the integration and compatibility of embedded sensing, transmission, and actuation systems. Various soft materials present different challenges, but also new opportunities, for novel fabrication techniques, integrated soft sensors, and embedded actuators. For instance, extensive research on silicone elastomers has led to the development of soft sensors based on closed channels filled with liquid metal conductors, as well as corresponding fluidic actuators by pressurizing cavities within the body. In this letter, we present a novel approach to soft robot fabrication using soft expanding foam as the base material. While recent research points to elastic foams as a means to reduce material, manufacturing costs, and robot mass, they have not been explored much in the literature. This letter presents fabrication and prototyping techniques for developing low-cost, custom-shaped soft robots from expanding polyurethane foam. We describe how to integrate user-defined routing points for transmission and actuation through cable-driven electrical actuation systems directly into the foam. Furthermore, we explore novel fabrication and prototyping techniques in order to build and integrate soft sensors into the foam substrate, which we demonstrate on soft robots varying in design complexity from a soft gripper to a soft “puppy.”