Active Oscillations of Elastic Membranes Arising from the Coupling with a Catalytic Reaction.

Soft fluidic machines increasingly rely on self-sustained oscillations to accomplish tasks autonomously without electronics or software. Typically, these oscillations arise from mechanical nonlinearities in complex geometries or relatively involved fluidic circuitry, and are passive in that they require external power sources. Here, we show that, by harnessing the coupling with a catalytic reaction, active oscillations can arise even in flat elastic membranes without fluidic circuits or external power. We embed a silver catalyst in a flat elastic membrane suspended over a pool of liquid hydrogen peroxide as fuel. When the fuel contacts the catalyst, it decomposes, releasing gases and generating pressure. We observe an oscillation where the reaction activates and deactivates spontaneously, causing the membrane to cyclically inflate and deflate for hours consecutively. Using experiments and a lumped-parameter model, we show that the oscillation arises from an interplay between catalyst capillarity, membrane stiffness, and venting resistance, which together induce negative feedback and separation of timescales. These results demonstrate an active oscillation in which the energy release is directly coupled to the oscillation dynamics. By embodying energy within the oscillation, we expand the library of phenomena to achieve self-oscillation in autonomous soft machines, opening avenues for elasto-chemical strategies for physical control.