Instability pathways of hydrogel microlenses under concentrated loadings.

We investigate the mechanical instabilities of hydrogel microlenses triggered by concentrated loadings. Depending on hydrogel microlenses, geometries, and loading conditions, a series of nontrivial instability pathways is observed, including transitions of localized polyhedral faceted shapes with multifold vertices created by bifurcation, snapping through curvature inversion and large load drop, and wrinkling driven by combined in-plane stretching and compression. These pathways reveal the richness of the mechanical behavior of hydrogel microlenses and provide potential strategies to control the design and shape of complex hydrogel microlenses. [ABSTRACT FROM AUTHOR]