Ultrastretchable, self-healable and adhesive composite organohydrogels with a fast response for human-machine interface applications

Hydrogel based flexible sensors have been considered as promising wearable devices in human-machine interactions, which are of great significance in mobile communications, personal healthcare, and intelligent robots. To meet the requirements of practical applications especially in harsh environments, a multifunctional strain sensor was designed and fabricated based on the polydopamine-reduced oxide graphene/poly(3,4-ethylenedioxythiophene):poly(4-styrene sulfonate) (PEDOT:PSS)/polyacrylamide composite organohydrogel (PCOH) using ethylene glycol (Eg)-H2O binary solvent as the replacement medium, which displayed an excellent anti-freezing property (-40 degrees C for 24 h) owing to the low freezing point of the Eg in the PCOH, high self-healing efficiency (92% tensile strength and 90% elongation at break), excellent stretchability (1350%), high sensitivity (a gauge factor of 3.19 with the strain ranging from 0 to 500%), fast response time (90 ms), long durability (800 cycles), and a wide temperature detection range (-40 degrees C to 60 degrees C), respectively. When used as a strain sensor, it was able to detect various human motions such as finger, wrist, and knee movements, and facial micro-expressions. Moreover, we also attached the flexible sensor to the yoga equipment or a neck brace for practical applications, and it could also detect the movements of the human body. Specifically, as a wearable human-machine interface device, a smart glove that takes advantage of the excellent properties of the PCOH was developed for hand gesture recognition via transmitting data to a smart phone with a real-time display via a bluetooth wireless system. Thus, these multifunctional PCOH based strain sensors have broad application prospects in human-machine interactions, sports training, and personal healthcare.