Flexible and Printed Microwave Plasmonic Sensor for Noninvasive Measurement

The printed electrodes for detecting direct current signal changes of human vital signs have been fully investigated. Here a flexible and printed microwave plasmonic sensor for detecting liquid solutions is proposed and demonstrated. The sensor for noninvasive measurement at microwave frequencies is based on the spoof localized surface plasmons resonator, which is composed of a metal corrugated ring fabricated on the flexible PET substrate using the inkjet printing technology. The winding-shaped polydimethylsiloxane (PDMS) microfluidic channel is interleaved with the corrugated ring to simulate the complicated blood vessel. The simulated results agree well with the experimental measurements. It shows that the measured resonance frequency offset of 147 MHz has been achieved when the microfluidic channel is filled with deionized water, which indicates that the flexible microwave biological sensor is feasible. The calculated figure of merit is as high as 1178. The sensor can find wider applications in the flexible and wearable device field for continuous health monitoring.