Topological adhesion II. Stretchable adhesion

When two stretchable materials (e.g., hydrogels, elastomers, and biological tissues) are adhered, the interface should be stretchable, without constraining the deformation and degrading adhesion. Here we develop methods to characterize stretchable adhesion. We do so by topological adhesion, using polyacrylamide hydrogels as adherends, chitosan as stitch polymers, and a change in the pH as a trigger. We prestretch the topohered hydrogels in several ways, and measure adhesion energy when the hydrogels are either in the un-stretched or the stretched state. Stretchable adhesion is achieved when the adhesion energy can maintain a similar level, insensitive to the prestretch. We study the mechanism of stretchable adhesion formed by the chitosan topohesive.