  Inertial cavitation in soft matter is an important phenomenon featured in a
wide array of biological and engineering processes. Recent advances in
experimental, theoretical, and numerical techniques have provided access into a
world full of nonlinear physics, yet most of our quantitative understanding to
date has been centered on a spherically symmetric description of the cavitation
process. However, cavitation bubble growth and collapse rarely occur in a
perfectly symmetrical fashion, particularly in soft materials. Predicting the
onset of dynamically arising, non-spherical instabilities has remained a
significant, unresolved challenge in part due to the additional constitutive
complexities introduced by the surrounding nonlinear viscoelastic solid. Here,
we provide a new theoretical model capable of accurately predicting the onset
of non-spherical instability shapes of a bubble in a soft material by
explicitly accounting for all pertinent nonlinear interactions between the
fluid-like cavitation bubble and the solid-like surroundings. Comparison
against high-resolution experimental images from laser-induced cavitation
events in a polyacrylamide (PA) hydrogel show excellent agreement.
Interestingly, and consistent with experimental findings, our model predicts
the emergence of various dynamic instability shapes for hoop stretch ratios
greater than one in contrast to most quasi-static investigations. Our new
theoretical framework not only provides unprecedented insight into the
cavitation dynamics in a soft solid, but it also provides a quantitative means
of interpreting bubble dynamics relevant to a wide array of engineering and
medical applications as well as natural phenomena.
