Swaying gel: chemo-mechanical self-oscillation based on dynamic buckling

Summary Self-oscillating systems are powerful tools for transducing static energy inputs into repetitive motions without the aid of external control units. The challenge in sustaining the far-from-equilibrium motion of an oscillating material is to avoid the tendency of reaching thermodynamic equilibrium or get pinned at steady states in the dynamic process. While living organisms present elegant strategies in myriad self-oscillations (e.g., peristalsis, cilia motion, homeostasis), current synthetic self-oscillating systems often rely on a fast actuation/reaction, to maintain the far-from-equilibrium motion, which prescribe highly specific chemical reactions and a material microstructure with limited stimuli and movement modes. Here, we present a dynamic buckling-based design for creating self-oscillating systems. The oscillation arises from the self-driven snap-through of a responsive hydrogel between bi-/multi-stable buckling configurations governed by a feedback loop. With broad choices of materials, tunable mechanics, and physical simplicity, this system opens a new venue for unlimited autonomous-oscillating materials applications.