Mechanics of crater-enabled dry adhesives

Soft adhesives that can attach to three-dimensional curvilinear surfaces historically have gained a myriad of attention from both scientific and technological perspectives. The rapid advances of bio-integrated devices in recent decades further led to a wealth of research in strategically designing soft adhesives with not only strong bonding capability but also easy-to-detach and reusable merits. The robust conformal contact, nondestructive debonding, and non-degrading repeatability together rule out the employment of chemical-based bonding agent, giving rise to a flurry of study on adhesives solely enabled by van der Waals (vdW) forces and/or suction effect, a.k.a. dry adhesives. In this dissertation, I first established an analytical framework for predicting the contact status of a thin elastic membrane conforming to a soft and rough substrate assuming vdW membrane/substrate interaction. Utilizing energy minimization method, I successfully predicted the fully conformed, partially conformed and non-conformed contact results, as validated by experimental observations. It was found that vdW adhesion alone is relatively weak to secure a conformal contact with rough substrates, especially when the system is subjected to external compressive strain. To enhance the interfacial adhesion, polymer surface engineered with concave domes, termed craters, recently emerges as a new type of dry adhesive. To quantitatively reveal adhesion mechanism in a cratered surface, I established a nonlinear elasticity framework for modeling the suction generation through an idealized loading-unloading process. Material properties, crater shape, air vs. liquid ambient, surface patterns and preloads are systematically investigated using finite element simulation and/or experimental approaches. The optimal topographical feathers of cratered surfaces with highest suction effect have been discovered. This dissertation offers an outlook for future research directions on crater-enabled dry adhesivesEngineering Mechanic