Stimuli-Detachable Adhesion of Hydrogels on Elastomer Substrate and Sequential Structural Change of the Soft Hybrids

Fabrication of soft hybrid incorporating hydrogel and elastomers have huge potential in various research fields such as soft electronics and robotics, microfluidics, and tissue engineering. Recently, robust adhesion of hydrogel on diverse elastomer surfaces has been achieved by activating surface-adsorbed hydrophobic initiators to graft hydrogel polymer chains from the elastomer substrate. In addition, a recently established adhesion approach permits the separation of the adhesion between elastomers and hydrogels when exposed to light. However, chemical stimuli-detachable strong adhesion between hydrogels and elastomers has not yet been demonstrated. In this study, we present a novel method for adhering hydrogels to elastomer surfaces. To enable chemically-detachable adhesion, various hydrogels are immersed, dipped or brushed with hydrogel-precursor solution containing reversible chemical linkers. Topological adhesion of hydrogels and elastomers are then obtained with the assist of hydrophobic initiator contained in elastomer substrate. The proposed method allows the separation of attached elastomers and hydrogel, upon different chemical stimulation. We first demonstrate that this technology is applicable to a wide variety of hydrogels and elastomers. We then demonstrate the sequential folding and on-demand structural change of such soft hybrids by utilizing the detachable adhesion of various stimuli-responsive hydrogels to elastomer surfaces.