Temperature‐Dependent Fatigue Characterization of Flexible Cellulose Nanocrystal Strain Sensor

Abstract The flexible cellulose nanocrystal (CNC) strain sensors have gained attention owing to their great promising in human motion detection, electronic skin, and soft robotics. However, the effect of bending on the mechanical performance of the sensor altered by the variation of temperature is a key limitation to their potential. Here, the temperature‐dependent bending fatigue of the CNC‐graphene oxide‐Ag nanoparticles (NPs) strain sensor is systematically investigated, in which the sensitivity of the sensor is attenuated to 20% with the decreasing temperature from 30 to −30 °C after bending over 10 000 times. The finite element studies and theoretical calculations indicate that the interfacial crack can be caused by the stiffness mismatch between the Ag NPs and CNC at different temperatures. Under room temperature, the destruction and recombination of the hydrogen bonds network at the interfacial crack can effectively increase the dissipation of energy and hinder the development of cracks with repetitive bending stress. However, under low temperature, such recombination processes are broken by the formation of ice crystals in the CNC/Ag NPs interfacial cracks. The ice crystals accelerate the crack propagation and eventually make the CNC sensor suffer from deterioration.