Thermally-activated biochemically-sustained reactor for soft fluidic actuation

Soft robots have shown remarkable distinct capabilities due to their high deformation. Recently increasing attention has been dedicated to developing fully soft robots to exploit their full potential, with a recognition that electronic powering may limit this achievement. Alternative powering sources compatible with soft robots have been identified such as combustion and chemical reactions. A further milestone to such systems would be to increase the controllability and responsiveness of their underlying reactions in order to achieve more complex behaviors for soft robots. In this paper, we present a thermally-activated reactor incorporating a biocompatible hydrogel valve that enables control of the biochemical reaction of sugar and yeast. The biochemical reaction is utilized to generate contained pressure, which in turn powers a fluidic soft actuator. Experiments were conducted to evaluate the response time of the hydrogel valves with three different crosslinker concentrations. Among the tested concentrations, we found that the lowest crosslinker concentration yielded the fastest response time of the valve at an ambient temperature of 50°C. We also evaluated the pressure generation capacity of the reactor, which can reach up to 0.22 bar, and demonstrated the thermoresponsive behavior of the reactor to trigger a biochemical reaction for powering a fluidic soft actuator. This work opens up the possibility to power and control tetherless and fully soft robots.