posted on 2019-12-19, 19:43authored byJie Wang, Fu Tang, Yue Wang, Qipeng Lu, Shuqi Liu, Lidong Li
Hydrogels that electronically respond to mechanical changes
can be used as strain sensors. However, these systems usually require
external power to convert changes in strain into electrical signals.
Here, a self-powered strain sensor is developed based on a gelatin-based
hydrogel and a galvanic cell. In the hydrogel matrix, hydrophobic
interactions and hydrogen bonding between tannic acid and gelatin
give the prepared hydrogel great potential for elongation (1600%).
The hydrogel also has a rapid self-healing ability (within 0.65 s)
and high self-healing efficiency (95%). The hydrogel operates as an
efficient electrolyte material and forms a hydrogel battery when assembled
with a thin layer of zinc and an air electrode. This device had excellent
tolerance to large compressional strain without sacrificing open-circuit
voltage. On the basis of this hydrogel battery, we fabricated a self-powered
strain sensor by connecting the hydrogel battery to a fixed resistor
to form a closed loop. By converting its chemical energy into electrical
energy, the self-powered sensor efficiently converted resistance changes,
caused by stretching or compression of the hydrogel, into changes
in the voltage output signals without external power. Owing to the
stretchability of the hydrogel, the self-powered sensor exhibited
good response and flexibility. Self-healing and continuous cycling
tests confirmed the long-term stability of the device. These properties
suggest that our self-powered sensor has a potential for applications
to portable and wearable electronic devices.