A modular approach to design multi-channel bistable valves for integrated pneumatically-driven soft robots via 3D-printing

A pneumatic system that transmits power via the force of compressed air is an essential component of an air-driven soft robot. Pneumatic valves are one of the key parts of this system. However, the development of soft or electronics-free valves for soft robotic applications is in its infancy, with only a few 2/2 way valves developed. Previous research has shown demands for a complex pneumatic system that can regulate the airflow in multiple channels or switching the pressure within a chamber between multiple states. Hardware redundancy is found in such complex pneumatic circuits if only 2/2 way valves are available for the system design. To increase the design freedom, this paper presents a modular approach that integrates multi-channel modular valve units and bi-stable structures for the conversion of pneumatic signals. By utilising soft-material 3D printing, the 3/2-way valve, 4/2-way valve and 5/2-way valve design are proposed in this paper to control multiple air channels simultaneously. The modular design of these 3D printed multi-port valves allows quick design and fabrication solutions of a complex electronics-free pneumatic system by reassembling different modular units of the valve. Experiment characterization of the multi-channel valves shows maximum allowable pressure at 187.2 kPa and a flow rate of 7.42 L/min under 50 kPa pressure loss. A demonstration of controlling four states of a dual-chamber soft robotic arm with only two modular multi-chamber valves was included, showing reduced valve units and overall weight compared to conventional electronics-free 2/2 way valves.