Nanocomposite hydrogels flexible sensors with functional cellulose nanocrystals for monitoring human motion and lactate in sweat

Cellulose nanocrystals (CNCs) are envisioned as superior building blocks for the manufacture of green functional materials and show great potential in flexible electronics. However, the development of a new generation of sensors with the ability to monitor human motion and sweat composition in an integrated manner holds significant promise. In this manuscript, an executable strategy was provided to construct the flexible sensors both for human motion monitoring and sweat sensing detection. The biocompatible, stretchable and self-healing hydrogels were proposed by introducing CNCs modified by polydopamine (PDA) and gold nanoparticles (AuNPs) into the poly (vinyl alcohol) PVA network, which provided enhanced conductivity and mechanical strength. The prepared hydrogels strain sensors displayed a high gauge factor (GF = 0.99) and fast response (160 ms). In addition, taking lactate oxidase (LOx) as a model enzyme, the obtained sweat sensors exhibited a low detection limit (0.31 mM) and an excellent linear correlation (0.9987) in a range of 0.5– 30 mM. The multifunctional sensing strategy provides a new and convenient approach to enable the sensitive detection of multiple components in sweat, as well as small or large human motion monitoring in the near future.