Edible Pneumatic Battery for Sustained and Repeated Robot Actuation

Energy production and storage represent challenges for biodegradable and edible technologies. Here, this study describes an edible energy storage and valve system designed to power pneumatically driven edible robots. The edible pneumatic battery exploits the acid-base neutralization reaction of food-grade reactants: under gravity, citric acid mixes with sodium bicarbonate powder to produce a steady release of carbon dioxide (CO₂) gas. The generated gas pressure causes deformation of a connected edible pneumatic actuator. When the gas pressure reaches a threshold, an edible valve automatically releases the pressurized gas, which lets the actuator return to its resting state. The entire system, whose characteristics are consistent with model estimates, is fully edible and enables self-sustained and repetitive bending motion of the edible actuator. This design is scalable in terms of sizes (30-50 mm diameter), operation time (20-650 s), and CO₂ gas generation rate (0.1-1.4 × 10^-3mol s^-1). Additionally, the actuator's motion can be programmed by modifying the orifice size or the fluidic resistance between the energy source, actuator, and valve. The system is validated by fabricating a fully edible system, and its application is showcased as a foot-pressed triggered edible actuator that mimics prey behavior to attract predators.