Frequency-enabled Decouplable Dual-modal Flexible Pressure and Temperature Sensor

Multifunctional sensory devices are emerging as a new trend in skin-inspired flexible electronics. Multimodal sensors show advanced features of simple device structure and ease of integration. However, multimodal sensors usually involve various sensing mechanisms and have difficulty in signal decoupling. In this letter, we used chitosan as a multifunctional layer to create a dual-modal flexible sensor. The performance of the pressure sensing exhibited excellent linearity ( $\text{R}^{2} = 0.997$ ), short response time (~37 ms), and uniform sensitivity over a wide range based on the contact surface mechanism. The temperature-sensitive proton conductivity of chitosan allowed a capacitive sensitivity of ~2.56 pF/°C. The frequency dependency of the capacitive output enabled modulations of the responses and a simple yet effective approach for decoupling the pressure and temperature responses with an average accuracy of ~92.3%. Such frequency-enabled decouplable dual-modal sensors show the advantages of simple device structure and multifunctional capabilities in skin-inspired electronics.