Tannic acid-Fe3+ activated rapid polymerization of ionic conductive hydrogels with high mechanical properties, self-healing, and self-adhesion for flexible wearable sensors

Wearable sensors based on hydrogels have been rapidly developed in many fields such as electronic skin, health detection, and human-machine interface. Wearable sensors for real-time monitoring of human activities require hydrogels with desirable mechanical strength, self-healing ability, sensing stability, and self-adhesion. However, to meet all these mentioned requirements, the preparation process of hydrogels is always complicated and timeconsuming. Herein, rapid polymerization hydrogels (PATG-B-Fe) for wearable sensors were designed from bacterial cellulose nanowhisker (BCW), tannic acid (TA), polyacrylic acid (PAA), Fe3+ and glycerol/water (Gly/ H2O). The dual catalysis system of TA-Fe3+ and Gly remarkably shortened the reaction time to 4 s at ambient temperature. With multiple hydrogen bonds and coordination among BCW-TA, PAA, and Fe3+, hydrogels exhibited an excellent trade-off between mechanical (stress of 203 kPa, elongation at break of 1950%) and selfhealing property (91% of efficiency). Strain sensors based on PATG-B-Fe hydrogels had good sensitivity (Gauge factor, maximum GF = 5.2 in 1200-1900% strain) and stable sensing properties at a wide temperature range ( 20-60 degrees C). Furthermore, strain sensors were adhered directly to skin to monitor large and subtle human movements. We believe PATG-B-Fe sensors may be a new horizon for the development of wearable and flexible electronic devices in the future.

Automated summary

Researchers have developed rapid polymerization hydrogels for wearable sensors, which exhibit excellent mechanical strength, self-healing ability, and stable sensing properties at a wide temperature range. This study provides a new direction for the development of wearable and flexible electronic devices.