Eur. Phys. J. E (2022) 45: 3
https://doi.org/10.1140/epje/s10189-021-00156-0

Regular Article - Soft Matter

Efficient snap-through of spherical caps by applying a localized curvature stimulus

¹ Department of Mechanical Engineering, Boston University, Boston, USA
² Department of Civil and Environmental Engineering, Princeton University, Princeton, USA
³ Yale University, New Haven, USA
⁴ Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, USA

^f dpholmes@bu.edu

Received: 14 September 2021
Accepted: 16 December 2021
Published online: 13 January 2022

Abstract

In bistable actuators and other engineered devices, a homogeneous stimulus (e.g., mechanical, chemical, thermal, or magnetic) is often applied to an entire shell to initiate a snap-through instability. In this work, we demonstrate that restricting the active area to the shell boundary allows for a large reduction in its size, thereby decreasing the energy input required to actuate the shell. To do so, we combine theory with 1D finite element simulations of spherical caps with a non-homogeneous distribution of stimulus-responsive material. We rely on the effective curvature stimulus, i.e., the natural curvature induced by the non-mechanical stimulus, which ensures that our results are entirely stimulus-agnostic. To validate our numerics and demonstrate this generality, we also perform two sets of experiments, wherein we use residual swelling of bilayer silicone elastomers—a process that mimics differential growth—as well as a magneto-elastomer to induce curvatures that cause snap-through. Our results elucidate the underlying mechanics, offering an intuitive route to optimal design for efficient snap-through.