Time-Dependent Pinning of Nanoblisters Confined by Two-Dimensional Sheets. Part 1: Scaling Law and Hydrostatic Pressure.

Understanding the mechanics of blisters is important for studying two-dimensional (2D) materials, where nanoscale blisters appear frequently in their heterostructures. It also benefits the understanding of a novel partial wetting phenomenon known as elastic wetting, where droplets are confined by thin films. In this two-part work, we study the static mechanics of nanoscale blisters confined between a 2D elastic sheet and its substrate (part 1) as well as their pinning/depinning dynamics (part 2). Here, in part 1, we investigate the morphology characteristics and hydrostatic pressures of the blisters by using atomic force microscopy (AFM) measurements and theoretical analysis. The morphology characteristics of the blisters are shown to be the interplay results of the elasticity of the capping sheet, the adhesion between the capping sheet and the substrate, and the interfacial tensions. A universal scaling law is observed for the blisters in the experiments. Our analyses show that the hydrostatic pressures inside the blisters can be estimated from their morphology characteristics. The reliability of such an estimation is verified by AFM indentation measurements of the hydrostatic pressures of a variety of blisters.