Microstructured biphasic hydrogels for highly sensitive and asymmetric sensors with temperature‐dependent sensitivity

Abstract

AbstractMicrofabrication of advanced architectures in flexible polymers has been a prevalent strategy to achieve high‐performance stretchable sensors. However, such microfabrication is usually challenging, requiring delicate synthesis with expensive instruments. This work utilizes the microphase separation in biphasic hydrogels (BHs) to conveniently achieve microstructured high‐performance sensors. Different microphase separated structures were observed in BH sensors depending on the oil/water ratios and temperature, resulting in many unexpected features. The BH sensors show excellent extensibility (1000%) and phenomenal mechanical durability (>1000 compressive cycles). The microphase separated non‐conductive phase (oil phase) and conductive phase (water phase) lead to structured conductive microchannels of water phase, providing the high resistive sensitivity (gauge factor > 50), superior than many reported flexible sensors. Interestingly, the sensory behaviors of BHs are drastically varied around body temperature due to the melting point of oil phases (eicosane, 36.8°C), making BH sensors highly suitable to monitor human bodily motions. The BH sensors are able to discern a series of subtle writings via resistive change attributed by the asymmetric deformation in soft microchannels from microphase separation. In this work, the BH sensors are successfully utilized to discern bodily motions, voice and writings around body temperature.