Interfacial fluid transport is a key to hydrogel bioadhesion

Significance Bioadhesive hydrogels capable of sticking to living tissues are of utmost interest for better-integrated implants and less invasive surgical techniques. Nevertheless, adhesion is most difficult to achieve and control on the wet surface of internal tissues. This work demonstrates that fluid transport across the tissue−hydrogel interface governs the creation of adhesion. Through ex vivo experiments and a simple model, we capture how the onset of adhesion depends on a competition between draining and wetting of the interface. This coupling between adhesion and interfacial transport provides a potent key to improve the accuracy of adhesion tests and to enhance the bioadhesive performance of hydrogels. We illustrate this potential in vivo by using superabsorbent hydrogel membranes to make strong liver adhesives. Attaching hydrogels to soft internal tissues is a key to the development of a number of biomedical devices. Nevertheless, the wet nature of hydrogels and tissues renders this adhesion most difficult to achieve and control. Here, we show that the transport of fluids across hydrogel−tissue interfaces plays a central role in adhesion. Using ex vivo peeling experiments on porcine liver, we characterized the adhesion between model hydrogel membranes and the liver capsule and parenchyma. By varying the contact time, the tissue hydration, and the swelling ratio of the hydrogel membrane, a transition between two peeling regimes is found: a lubricated regime where a liquid layer wets the interface, yielding low adhesion energies (0.1 J/m2 to 1 J/m2), and an adhesive regime with a solid binding between hydrogel and tissues and higher adhesion energies (1 J/m2 to 10 J/m2). We show that this transition corresponds to a draining of the interface inducing a local dehydration of the tissues, which become intrinsically adhesive. A simple model taking into account the microanatomy of tissues captures the transition for both the liver capsule and parenchyma. In vivo experiments demonstrate that this effect still holds on actively hydrated tissues like the liver capsule and show that adhesion can be strongly enhanced when using superabsorbent hydrogel meshes. These results shed light on the design of predictive bioadhesion tests as well as on the development of improved bioadhesive strategies exploiting interfacial fluid transport.