Soft Wireless Battery-Free UHF RFID Stretchable Sensor Based on Microfluidic Technology

Stretchable microfluidic sensors have recently been developed and employed in many sensing applications. However, they are still in their early stage of development and facing considerable challenges, such as practical system integration due to the limitation of costs, wired connections, and sensitivity. In this paper, we present a compact soft wireless battery-free radio frequency identification (RFID) stretchable sensor based on microfluidic technology. The proposed RFID sensor has high sensitivity and is able to be stretched to 160% of its original size. Moreover, the sensor is completely wireless powered and battery-free. It can be fully embedded into sensor carriers, such as robots to eliminate wires, reduce the weight, and increase the agility. Difference to known received signal strength indicator (RSSI) techniques for RFID sensing monitoring, resonance frequency shift is used in this paper, significantly increasing the measurement accuracy, usefulness, and reliability for many practical applications.