Iontronic capacitance-enhanced LC wireless passive pressure sensor for high-performance flexible sensing

Wireless passive sensors based on inductor-capacitor (LC) circuits have been an area of intense research in wearable electronics because of their battery-free and wirelessly connected operation. However, significant challenges remain in achieving high sensitivity and long-range performance for such device. In this study, we present a bilayer coils LC wireless passive iontronic pressure sensor (BWIPS) that overcomes these limitations. The bilayer coils strategy enhances the coupling effect and extends the operating distance up to 20 mm. Meanwhile, the capacitive iontronic pressure sensor (IPS) achieves high sensitivity (0.54 kPa−1) and a broad sensing range (400 kPa). By integrating bilayer coils and IPS, the BWIPS exhibits a remarkable sensitivity of −37.4 kHz kPa−1. Furthermore, the flexibility of the sensor allows it to maintain its resonant frequency regardless of various bending radius, making it suitable for use in prosthetic devices. Our BWIPS technology holds great potential for advancing the development of wireless passive sensors in the future, particularly in applications that require high sensitivity, broad sensing range, and non-contact detection at a distance.