Biomimetic Epidermal Sensors Assembled from Polydopamine-Modified Reduced Graphene Oxide/Polyvinyl Alcohol Hydrogels for Real-time Monitoring of Human Motions

AbstractConductive hydrogel-based epidermal strain sensors can generate repeatable electrical changes upon mechanical deformations for indication of the skin’s physiological condition. However, it remains challenging for many conductive hydrogel sensors in terms of biomechanical mismatch with skin tissues and unstable resistance variation response, resulting in unconformable deformations with the epidermis and dermis, and consequently generating inaccurate monitoring of human movements. Herein, a conductive hydrogel with high-matched skin is fabricated from dynamic hydrogen bonds and nanocrystallites of polydopamine-modified reduced graphene oxide nanosheets (PDA-rGO) composited polyvinyl alcohol, namely PDA-rGO/PVA hydrogel. The PDA-rGO provides a large amount of dynamic hydrogen-bonding interactions in hydrogel, resulting in skin-matching modulus (78 kPa) and stretchability. Moreover, the resultant hydrogel possesses excellent cytocompatibility, conductivity (0.87 S/m), and high sensitivity (gauge factor of compression: 20) at low strain and outstanding linearity at high strains as well as stable resistance variation response. These desirable properties enable applications of the PDA-rGO/PVA hydrogel as skin-friendly wearable sensor for real-time and accurate detection of both large-scale joint movements and tiny physiological signals, including bending and relaxing of fingers, wrist, elbow and knee joints, and wrist pulse and swallowing. Moreover, such hydrogel is integrated to a 2D sensor array that monitors strains or pressures in the two dimensions, which is promising for electronic skin, biosensors, human-machine interfaces, and wearable electronic devices.

https://pubs.rsc.org/en/content/articlelanding/2020/tb/d0tb02100h#!divAbstract