An ultrastretchable
thermistor that combines intrinsic stretchability,
thermal sensitivity, transparency, and self-healing capability is
fabricated. It is found the polyacrylamide/carrageenan double network
(DN) hydrogel is highly sensitive to temperature and therefore can
be exploited as a novel channel material for a thermistor. This thermistor
can be stretched from 0 to 330% strain with the sensitivity as high
as 2.6%/°C at extreme 200% strain. Noticeably, the mechanical,
electrical, and thermal sensing properties of the DN hydrogel can
be self-healed, analogous to the self-healing capability of human
skin. The large mechanical deformations, such as flexion and twist
with large angles, do not affect the thermal sensitivity. Good flexibility
enables the thermistor to be attached on nonplanar curvilinear surfaces
for practical temperature detection. Remarkably, the thermal sensitivity
can be improved by introducing mechanical strain, making the sensitivity
programmable. This thermistor with tunable sensitivity is advantageous
over traditional rigid thermistors that lack flexibility in adjusting
their sensitivity. In addition to superior sensitivity and stretchability
compared with traditional thermistors, this DN hydrogel-based thermistor
provides additional advantages of good transparency and self-healing
ability, enabling it to be potentially integrated in soft robots to
grasp real world information for guiding their actions
