关键词: LC应变传感器, 丝网印刷, 银, 液态金属, 玉米醇溶蛋白超细纤维

Abstract: Biological flexible sensors can monitor the wearer's health and environment in real time, attracting significant academic interests. They have broad potential applications in areas such as medical diagnostics and fitness monitoring. However, traditional biological flexible sensors usually require cables to connect to external devices, making them complex, bulky, and short-lived. Especially for implanted active sensors, the need for regular battery replacement can cause additional harm to patients. Passive wireless sensors, on the other hand, do not require power connections, electrodes, or wires. They are lightweight, compact, simple in structure, and have a longer lifespan. LC resonant sensors, which are inductive field sensors, have a simpler structure compared to harmonic sensors, as they do not require diodes. Both solid and liquid metals are widely used to construct the sensing layer of sensors. Solid metals can offer high sensitivities but are brittle, limiting the sensor's working range. Liquid metals (LM), with their high flexibility, fluidity, and conductivity, can adapt to complex shapes and dynamic environments, providing a broader operational range but limited sensitivity. To achieve both high sensitivity and a broad working range in flexible LC passive wireless strain sensors, this study employs screen printing and mask spraying techniques to construct a patterned solid-liquid metal composite sensing layer on a ZE ultrafine fiber substrate. By combining the sensing advantages of solid and liquid metals, the sensor's performance is optimized. ZE ultrafine fibers are an ideal biomedical flexible substrate due to their natural flexibility, high surface area, biocompatibility, and biodegradability. A planar spiral sensing coil is formed by combining screen-printed solid silver (Ag) with mask-sprayed liquid metal in a segmented pattern, integrated with the ultrafine fiber substrate. The screen printing and spraying processes are simple, low-cost, and allow for rapid patterning of the sensing layer. Experimental results show that the choice of sensing layer materials and the solid/liquid metal ratio significantly impact the sensor's initial resistance and sensitivity. The optimal Ag/LM ratio is 2:1, balancing sensitivity (28.6 MHz) and operational range (82%). The study also examines how the sensor's microstructure and porosity affect its gas permeability. The results indicate that the Ag/LM composite design not only enhances the sensor's performance but also maintains breathability, making it suitable for biomedical applications that require high comfort and functionality. The combination of degradable ZE substrate and unique solid-liquid metal composite design gives this sensor potential applications in biomedical monitoring, environmental sensing, and wearable devices. The research integrates the advantages of solid and liquid metals into a single sensing layer, offering a new approach to developing flexible strain biological sensors.

Key words: LC strain sensor, screen printing, silver, liquid metal, ZE ultrafine fibers