Spatiotemporally Programmable Surfaces via Viscoelastic Shell Snapping

Many species can dynamically alter their skin textures to enhance their motility and survivability. Despite the enormous efforts on designing bio‐inspired materials with tunable surface textures, developing spatiotemporally programmable and reconfigurable textural morphing without complex control remains challenging. Herein, a design strategy is proposed to achieve surfaces with such properties. The surfaces comprise an array of unit cells with broadly tailored temporal responses. By arranging the unit cells differently, the surfaces can exhibit various spatiotemporal responses, which can be easily reconfigured by disassembling and rearranging the unit cells. Specifically, viscoelastic shells as the unit cells is adopted, which can be pneumatically actuated to a concave state, and recover the initial convex state sometime after the load is removed. It is shown computationally and experimentally that the recovery time can be widely tuned by the geometry and material viscoelasticity of the shells. By assembling such shells with different recovery times, surfaces with pre‐programmed spatiotemporal textural morphing under simple pneumatic actuation is built, and temporal evolution of patterns, such as digit numbers and emoji, and spatiotemporal control of friction are demonstrated. This work opens up new avenues in designing spatiotemporal morphing surfaces that could be employed for programming mechanical, optical, and electrical properties. A preprint version of the article can be found at: https://www.authorea.com/doi/full/10.22541/au.164020946.62560710. A design strategy for reconfigurable surfaces exhibiting spatiotemporally programmable textural morphing under simple control is proposed. Viscoelastic shells that can temporarily stay concave before recovering the initial convex state without external loads are chosen as unit cells. By integrating such shells with broadly tuned recovery time by geometry and material viscoelasticity, surfaces exhibiting spatiotemporal evolution of patterns and friction are created.