Bioinspired nanocellulose-based ultrathin hydrogel bioadhesives with sweat-resistant properties.

Hydrogels have gained prominence as a distinctive material for smart healthcare devices and wearable electronics, owing to their inherent biocompatibility, tissue-like mechanical properties and superior water and oxygen permeability. In most application scenarios, hydrogels are required to have certain adhesion properties. However, current hydrogel adhesive systems are fundamentally constrained by two intrinsic material restrictions: low mechanical strength, and compromised adhesion in humid environments (under conditions such as sweating and bleeding), which severely restrict their practical applications. Inspired by the covalent and physical synergistic adhesion strategy of mussels and the interfacial water-capturing mechanism of spiderwebs, we designed and fabricated an ultrathin poly (acrylic acid) (PAA)/N-hydroxysuccinimide (NHS)/cellulose nanocrystal (CNC) composite hydrogel (PNCGels) tape. This PNCGels tape adopts a dry crosslinking mode, which enables the carboxyl groups in the hydrogel rapidly form physical interactions such as hydrogen bonds with tissue surface within less than 5 s. Subsequently, the NHS ester groups grafted onto PAA couple covalently with primary amine groups in the tissue. Additionally, the CNC nanofillers enhance cohesive strength by reconstructing a dynamic hydrogen-bonding network to balance adhesion, which ensures stable adhesion even in the presence of sweat. The resultant PNCGels tape displayed remarkable wearability (thickness of only 250 μm), excellent adhesive properties (adhesion strength: 128 kPa), good mechanical performance (tensile strength: 1400 kPa). The integrated features of ultra-slimness, high toughness, and humidity-resistant adhesion provide a transformative platform for advanced applications, including smart wound dressings (hemostasis, on-demand removal) and motion sensing technologies.