Single-Input Control of Multiple Fluid-Driven Elastic Actuators via Interaction Between Bistability and Viscosity

A leading concept in soft robotics actuation, as well as in microfluidics applications such as valves in lab-on-a-chip devices, is applying pressurized flow in cavities embedded within elastic bodies. Generating complex deformation patterns typically requires control of several inputs, which greatly complicates the system's operation. In this study, we present a novel method for single-input control of a serial chain of bistable elastic chambers connected by thin tubes. Controlling a single flow rate at the chain's inlet, we induce an irreversible sequence of transitions that can reach any desired state combination of all bistable elements. Mathematical formulation and analysis of the system's dynamics reveal that these transitions are enabled, thanks to bistability combined with pressure lag induced by viscous resistance. The results are demonstrated through numerical simulations combined with experiments for chains of up to five chambers, using water-diluted glycerol as the injected fluid. The proposed technique has a promising potential for development of sophisticated soft actuators with minimalistic control.