Light-induced reversible assembly and actuation in ultrafast Ca ²⁺ -driven chemomechanical protein networks

Programming ultrafast, reversible motions in soft materials has remained a challenge in active matter and biomimetic design. Here, we present a light-controlled chemomechanical network based on Tetrahymena thermophila calcium-binding protein 2 (Tcb2), a Ca ²⁺ -sensitive contractile protein. These networks, driven by Ca ²⁺ -triggered structural rearrangements, exhibit dynamic self-assembly, spatiotemporal growth, and contraction rates up to tenfold faster than ATP-driven actomyosin systems with non-muscle myosin II motors. By coupling light-sensitive chelators for optically triggered Ca ²⁺ release, we achieve precise, reversible growth and contractility of Tcb2 networks, revealing emergent phenomena such as boundary-localized active regions and density gradient-driven reversals in motion. A coupled reaction-diffusion and viscoelastic model explains these dynamics, highlighting the interplay between chemical network assembly and mechanical response. We further demonstrate active transport of particles via network-mediated forces in vitro and implement reinforcement learning to program sub-second, spatiotemporal actuation in silico . These results establish a platform for designing responsive active materials with ultrafast chemomechanical dynamics and tunable optical control, with applications in synthetic cells, sub-cellular force generation, and programmable biomaterials.