Interfacial fatigue fracture of tissue adhesive hydrogels

Tissue adhesive hydrogels find increasing use in the clinic, but their response to prolonged cyclic deformation remains unexplored. The lack of understanding hinders the development and application of tissue adhesive hydrogels, particularly in the applications interfacing with repeatedly deforming tissues such as heart and lung. Here we study the interfacial fatigue fracture of a tissue adhesive hydrogel based on tough hydrogel, called tough adhesive (TA), using a fracture mechanics approach. We perform modified lap-shear tests with three types of loading (e.g., monotonic, static, and cyclic loads). We observe shakedown of the load-displacement curves during cycling and two interfacial fracture phenomena: fast debonding and interfacial fatigue fracture. We confirm the existence of a fatigue threshold (24.4 Jm(-2)) for the TA-skin interface, below which the interface is immune against prolonged cyclic deformation. The threshold is lower than the adhesion energy (580 Jm-2) for fast debonding. We also compare the interfacial fatigue fracture with the fatigue of bulk hydrogels. This work will promote further mechanistic investigation on interfacial fatigue fracture and the development of fatigue-resistant tissue adhesives. (C) 2019 Elsevier Ltd. All rights reserved.