An intrinsically stretchable humidity sensor based on anti-drying, self-healing and transparent organohydrogels

• Published in: Materials horizons Vol. 6; no. 3; pp. 595 - 603
• Main Authors: Wu, Jin, Wu, Zixuan, Xu, Huihua, Wu, Qian, Liu, Chuan, Yang, Bo-Ru, Gui, Xuchun, Xie, Xi, Tao, Kai, Shen, Yi, Miao, Jianmin, Norford, Leslie K.
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 01.01.2019
• Subjects: Carrageenan; Chemical bonds; Drying; Ethylene glycol; Humidity; Hydrogen bonds; Linearity; Recovery time; Relative humidity; Resistance; Sensitivity enhancement; Sensors; Solvents; Stretchability; Sulfur trioxide; Water chemistry
• ISSN: 2051-6347; 2051-6355
• DOI: 10.1039/C8MH01160E

Stretchability and self-healing ability are essential attributes of modern electronic sensors for wearable applications. Herein, intrinsically ultrastretchable, self-healing and transparent humidity sensors composed of ionic κ-carrageenan/polyacrylamide (PAM) double network (DN) organohydrogels are fabricated via a facile solvent-exchange strategy. Hygroscopic ethylene glycol (EG) and glycerol (Gly) are introduced in the organohydrogels to promote both anti-drying and humidity sensing capabilities. The organohydrogel sensors display unprecedented stretchability (1225% strain) and excellent sensing performance, including fast response (0.27 s) and recovery time (0.3 s), wide relative humidity (RH) detection range (4–90%), stability and linearity. The conductance of Gly-DN sensors increases more than 543 times with increasing RH from 4% to 90%. With sufficient sensitivity, the humidity sensors can monitor human respiration with stable and repeatable output. The enhanced sensitivity and moisture-holding ability are attributed to the ready formation of hydrogen bonds between water molecules and enormous hydrophilic groups, including –OH, SO 3 − and –NH 2 , in the elaborate polymer networks and binary solvent. The hindering effect of polymer chains on the transport of conductive ions plays a key role in producing a transducing signal, which is proposed as the mechanism of the novel sensors.