Highly transparent, stretchable, and rapid self-healing polyvinyl alcohol/cellulose nanofibril hydrogel sensors for sensitive pressure sensing and human motion detection

• Published in: Sensors and actuators. B, Chemical Chemical, 2019-09, Vol.295, p.159-167
• Main Authors: Jing, Xin, Li, Heng, Mi, Hao-Yang, Liu, Yue-Jun, Feng, Pei-Yong, Tan, Yi-Min, Turng, Lih-Sheng
• Format: Article
• Language: English
• Subjects: Bonding; Cellulose; Crosslinking; Dimensional stability; Elongation; Fibroblasts; Head movement; Health care; High sensitivity; Human motion; Hydrogels; Hydrogen bonds; Knee; Motion perception; Polyvinyl alcohol; Self-healing; Sensitivity; Sensors; Stretchable hydrogel; Transparent; Water drops; Wearable technology
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2019.05.082

[Display omitted] •The prepared hydrogel showed a great self-healing ability and spontaneously self-healed within 15 s.•The prepared hydrogel was highly transparent, with transmittance reaching as high as 90%.•The developed hydrogel sensor was able to sense very subtle external pressure such as water drop.•The sensor worked stably on the detection of human motions such as finger, knee or elbow movements. Wearable sensors have emerged as favored novel devices for human healthcare. Current sensors, however, suffer from low sensitivity, non-transparency, and lack of self-healing ability. In this study, we synthesized a polyvinyl alcohol/cellulose nanofibril (PVA/CNF) hydrogel with dual-crosslinked networks for highly transparent, stretchable, and self-healing pressure and strain sensors. The hydrogel contains dynamic borate bonds, metal–carboxylate coordination bonds, and hydrogen bonds, all of which contribute to the hydrogel’s superior dimensional stability, mechanical strength and flexibility, and spontaneous self-healing ability as compared to traditional PVA hydrogels. The developed hydrogel has a moderate modulus of 11.2 kPa, and a high elongation rate of 1900%. It spontaneously self-heals within 15 s upon contact without any external stimuli, has a high transmittance of over 90%, and has excellent compatibility with human fibroblasts. The capacitive sensor developed based on the PVA/CNF hydrogel has high sensitivity to very subtle pressure changes, such as small water droplets. When used as a strain sensor, it was capable of detecting and monitoring various human motions such as finger, knee, elbow, and head movements, breathing, and gentle tapping. The developed hydrogel and sensors not only show great potential in electronic skin, personal healthcare, and wearable devices, but may also inspire the development of transparent, intelligent skin-like sensors.