NFC Coils with Resistance Sensitivity for Wearable Applications

This paper proposes a near-field communications (NFC) system with resistance sensitivity for wearable applications. This NFC system is made up of two planar spiral coils, both established on a flexible substrate Polydimethylsiloxane (PDMS) with a size of 22.5 mm x 29 mm. To be sensitive to the pressure changing, one planar spiral antenna is connected with a pressure strain resistor, serving as a tag, and the other antenna is fed with cable, serving as a receiver. In this way, the pressure changing of the surrounding environment which causes the variation of the resistor value can be reflected on the shift of the antenna resonance.