Flexible LC Sensor Array for Wireless Multizone Pressure Monitoring

Flexible pressure sensors have shown great potential in medical field due to the advantages of excellent flexibility and comfortable wearing. In this paper, a flexible inductive-capacitive (LC) sensor array is proposed for wireless multi-zone pressure monitoring. It consists of three pressure-sensitive LC sensors that operate in non-overlapping frequency channels. Nano-Ag particles are inkjet printed on polyimide (PI) substrate to fabricate the LC circuits. A thin layer of Polydimethylsiloxane (PDMS) is spin-coated onto the circuit, serving as both an electrical insulating layer to prevent shorting out and a deformable dielectric layer between the two capacitor plates when the circuit is folded. Benefiting from the folding design, the PI substrate acts as an external package that provides optimal protection for the entire device. Simulations and experiments are conducted to evaluate the performance in wireless multi-zone pressure monitoring using the LC sensor array. The results indicate a sensitivity of up to 0.235 MHz/kPa in the range of 0-100 kPa, as well as stability with a bias less than 0.15 MHz over 300 pressure cycles. Furthermore, the sensor array is successfully applied to detect finger flexion, smile, and swallow, showing a promising potential in human health monitoring.