Fig. 6.

Signal change of all-wood hydrogel (with 8.7 wt% lignin, 10% PVA, 4 days for salting in sodium sulfate solution at room temperature) for real-time monitoring of various human motions. a Assembly process of the all-wood hydrogel sensor. b Real-time signal changes ((R − R₀)/R₀) of all-wood hydrogels bent repeatedly in the longitudinal and radial directions. The hydrogel can be used to monitor subtle muscle movements in real time, such as c finger flexion, d pulse beats, e swallowing, and f throat vibrations, as when a person says “An Qi” four times in a row