Oscillating Membranes: autonomous shape-transforming sheets via chemomechanical "metabolism"
 

Host: Sarah Keller
 

Abstract: Living organisms have mastered the dynamic control of residual stresses within sheets to induce shape transformation and locomotion. For instance, the spatiotemporal pattern of action-potential in a heart results in a dynamical stress field that leads to shape changes and biological function. Such out-of-equilibrium structures inspired the emerging field of soft robotics. However, state-of-the-art attempts to replicate this ability in synthetic materials are still lacking.
In this talk, I will present the first autonomously shape-shifting sheets: thin sheets of responsive gel that shrink and swell in response to the phase of an oscillatory chemical (Belousov-Zhabotinsky) reaction[1]. Propagating reaction-diffusion fronts induce localized deformation of the gel. I will show that these localized deformations prescribe a spatiotemporal pattern of Gaussian-curvature, leading to time-periodic global shape changes. Next, I will present the computational tools and experimental protocols needed to control this system: principally the relationship between the Gaussian-curvature and the reaction phase, and optical imprinting of the wave pattern. Finally, I will present our current journey towards autonomous soft swimmers.
Together, these results demonstrate a route for modelling and developing fully autonomous soft machines mimicking some of the locomotive capabilities of living organisms.
[1] IL, Robert Deegan, and Eran Sharon, Phys. Rev. Lett. 2020 125(17) 178001.