Fluid-induced large deformation at soft material interfaces with blisters and craters

This dissertation focuses on fluid-induced large deformation at interfaces where at least one material is soft, i.e. materials with low Young’s modulus and capable of large deformation. Soft materials are finding important applications in many emerging fields such as soft electronics, soft robotics, and bio-integrated devices. Most often, soft materials have to form interfaces with other materials where fluids may present. Such interfacial fluids may affect attachment in negative or positive ways but so far, theoretical studies are rare due to the difficulties associated with large deformation and elasto-capillary effects. Regarding the dynamics of fluid flow as a sequence of static equilibrium states, it becomes sufficient to analyze problems in the context of solid mechanics. This dissertation provides nonlinear solutions to such classes of problems through two examples – interfacial blisters and craters. When a soft membrane covers a flat surface, interfacial blisters inflated by increasing amount of interfacial fluids may cause detachment between the membrane and the substrate. I formulated a nonlinear membrane theory to characterize the bulging and bulging-induced delamination process of the soft membrane. Elasto-capillary effects are considered due to their significance at small-scales. Solutions for both rigid and soft substrates are obtained. For rigid substrates, a variety of boundary conditions is modeled. In the second example, the crater problem is inspired by emerging experimental evidence that enhanced adhesion has been measured when a soft material with surface craters is pressed against a rigid surface. I established a nonlinear elasticity framework to model suction forces generated by the loading and unloading process. Both ideal gas and incompressible fluids have been considered. This framework has been validated by experiments and has been applied to optimize the design of craters. The nonlinear theoretical frameworks established in this dissertation offer methodologies to model and understand other soft material interfaces with interfacial fluids.