Instant, Tough, Noncovalent Adhesion

Noncovalent adhesion has long been developed for numerous applications, including pressure-sensitive adhesives, wound closure, and drug delivery. Recent advances highlight an urgent need: a general principle to guide the development of instant, tough, noncovalent adhesion. Here, we show that noncovalent adhesion can be both instant and tough by separately selecting two types of noncovalent bonds for distinct functions: tougheners and interlinks. We demonstrate the principle using a hydrogel with a covalent polymer network and noncovalent tougheners, adhering another material through noncovalent interlinks. The adhesion is instant if the interlinks form fast. When an external force separates the adhesion, the covalent polymer network transmits the force through the bulk of the hydrogel to the front of the separation. The adhesion is tough if the interlinks are strong enough for many tougheners to unzip. Our best result achieves adhesion energy above 750 J/m 2 within seconds. The adhesion detaches in response to a cue, such as a change in pH or temperature. We identify several topologies of noncovalent adhesion and demonstrate them in the form of tape, powder, brush, solution, and interpolymer complex. The abundant diversity of noncovalent bonds offers enormous design space to create instant, tough, noncovalent adhesion for engineering and medicine.