Robust hydrogel-integrated microsystems enabled by enhanced interfacial bonding strength

Abstract

Noncovalent hydrogels, compared to covalent hydrogels, have distinctive advantages including biocompatibility and self-healing property but tend to have poor mechanical robustness, thus restricting their application spectrum. A clue to increase utility of such soft hydrogels without chemical bulk modification can be witnessed in biological organ walls where soft mucous epithelial layers are juxtaposed with tough connective tissues. Perhaps, similarly, bonding noncovalent hydrogels to stronger materials, such as tough hydrogels, might be a viable approach for increasing stability and scalability as well as creating novel functions for hydrogel-based systems. However when attempting to bond these two materials, each of the four existing hydrogel-hydrogel bonding method has practical shortcomings. In this work, we introduce a mucosa-inspired bonding method that realizes interfacial bonding of noncovalent hydrogels to tough, hybrid hydrogels without external glue or bulk modification of the noncovalent gel while preserving interfacial micropatterns. The procedure is simple and we confirmed broad applicability with various noncovalent hydrogels and tough hydrogels. We demonstrated the utility of our bonding method with novel applications regarding in vitro assay, soft robotics and biologically inspired systems.