Bioinspired adaptive lipid-integrated bilayer coating for enhancing dynamic water retention in hydrogel-based flexible sensors.

While hydrogel-based flexible sensors find extensive applications in fields such as medicine and robotics, their performance can be hindered by the rapid evaporation of water, leading to diminished sensitivity and mechanical durability. Despite the exploration of some effective solutions, such as introducing organic solvents, electrolytes, and elastomer composites, these approaches still suffer from problems including diminished conductivity, interface misalignment, and insufficient protection under dynamic conditions. Inspired by cell membrane structures, we developed an adaptive lipid-integrated bilayer coating (ALIBC) to enhance water retention in hydrogel-based sensors. Lipid layers and long-chain amphiphilic molecules are used as compact coating and anchoring agents on the hydrogel surface, mimicking the roles of lipids and membrane proteins in cell membranes, while spare lipids from aggregates within hydrogels can migrate to the surface to combat dehydration under deformation. This lipid-integrated bilayer coating prevents the water evaporation of hydrogels at both static and dynamic states without affecting the inherent flexibility, conductivity, and no cytotoxicity. Hydrogel-based sensors with ALIBC exhibited significantly enhanced performance in conditions of body temperature, extensive deformation, and long-term dynamic sensing. This work presents a general approach for precisely controlling the water-retaining capacity of hydrogels and hydrogel-based sensors without compromising their intrinsic physical properties.