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

TL;DR

This paper demonstrates that applying a localized curvature stimulus at the boundary of spherical caps significantly reduces energy input for snap-through, combining theory, simulations, and experiments with various stimuli.

Contribution

It introduces a boundary-focused stimulus approach for efficient snap-through, validated through simulations and experiments with different stimulus methods.

Findings

Localized boundary stimulus reduces energy required for snap-through

The approach is stimulus-agnostic, applicable to various stimuli

Experimental validation confirms simulation predictions

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.