Bending stiffness of ionically bonded mica multilayers told by its bubbles

Revealing the bending stiffness of layered materials is crucial for guiding their applications with notable out-of-plane deformation, such as in flexible electronics. To this end, dedicated methods have been developed, but usually involving precise manipulation of atomically thin flakes or cross-section characterization with atomic resolution, hindering their widespread adoption. Here, we utilize mica as a case study to demonstrate that bubbles spontaneously formed during mechanical exfoliation provide a facile but reliable approach for investigating its bending mechanics. Through topographical analysis of bubbles with widely distributed sizes, a bending stiffness is extracted following a nonlinear plate theory. The less bending stiffness than the ideal non-linear plate solution indicates a moderate interlayer slip, as confirmed by molecular dynamics simulations. The interlayer shear coefficient for mica is higher than that for multilayer graphene, which is attributed to its strong interfacial shear strength inheriting from its interlayer ionic bonding.