  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.
