A Highly Stretchable, Real-Time Self-Healable Hydrogel Adhesive Matrix for Tissue Patches and Flexible Electronics

The development of biocompatible self-healable hydrogel adhesives for skin or wet, stretchable surfaces in air or under water is highly desirable for various biomedical applications ranging from skin patches to bioelectronics. However, it has been proven to be very challenging because most existing hydrogel adhesives are cytotoxic, or poorly adhere to dynamic or stretchable surfaces in wet environments. In this study, multifunctional hydrogel adhesives derived from silk fibroin (SF) and tannic acid (TA) are effectively constructed with high extensibility (i.e., up to 32 000%), real-time self-healing capability, underwater adhesivity, water-sealing ability, biocompatibility, and antibiotic properties. According to all-atom molecular dynamics simulation studies, the properties of the hydrogel adhesives, especially high extensibility, are mainly attributed to the hydrogen bonds between TA and the SF chains in water, and water and TA molecules can result in loose assemblies with fewer β-sheets, and more random coils in the SF. Conductivity can also be easily introduced to the adhesive matrix and adjusted when the strain of the adhesives occurs. Considering that it has multiple functions and can be efficiently prepared, the proposed hydrogel adhesives have the potential for future medical applications, such as tissue adhesives and integrated bioelectronics.