Biomimetic Wet Adhesion of Viscoelastic Liquid Films Anchored on Micropatterned Elastic Substrates

摘要

Inspired by the natural adhesives in the toenpads of arthropods and some other animals, we explore theneffectiveness and peel failure of a thin viscoelastic liquid filmnanchored on a micropatterned elastic surface. In particular, wenfocus on the role of the substrate pattern in adhesion energy ofnthe liquid layer and in allowing its clean separation withoutncohesive failure. Peel tests on the microfabricated wetnadhesives showed two distinct modes of adhesive (interfacial)nand cohesive (liquid bulk) failures depending on the patternndimensions. The adhesion energy of a viscoelastic liquid layernon an optimized micropatterned elastic substrate is ∼3.5 times higher than that of a control flat bilayer and ∼26 times higher thannthat of a viscoelastic film on a rigid substrate. Adhesive liquid layers anchored by narrow microchannels undergo clean, reversiblenadhesive failure rather than the cohesive failure seen on flat substrates. An increase in the channel width engenders cohesivenfailure in which droplets of the wet adhesive remain on the peeled surface.