A printed flexible temperature sensor integrated with conductive polyaniline nanowires for wearable applications

Background: Flexible temperature sensors are needed for applications requiring lightweight, conformable, and low-power sensing platforms, and printed formats offer a route toward low-cost fabrication, mechanical flexibility, and integration with compact wireless electronics.

Methods: Two resistive temperature sensors were compared: a control consisting of a silver-ink resistor pattern printed on polyethylene terephthalate (PET), and an identical sensor coated with conductive polyaniline (PANI) nanowires. Both were characterized over 20–70 °C, a range encompassing skin-adjacent temperatures, under stepwise heating and cooling. A low-power wireless readout combining an AD5933 impedance analyzer with an nRF52832 microcontroller and Bluetooth Low Energy was developed, and the two devices were compared using the Analytic Hierarchy Process (AHP).

Results: Each sensor showed positive-temperature-coefficient behavior with a near-linear resistance–temperature response. PANI nanowire integration improved linearity, raising the coefficient of determination from 0.91 to 0.94 on heating and from 0.90 to 0.98 on cooling, and halved the hysteresis between heating and cooling branches. The wireless readout measured reference resistors to within 1% of multimeter values at a base current draw of 6.62 mA. The AHP ranked the PANI-modified device higher than the control (0.735 vs 0.265).

Conclusions: PANI nanowire coatings improve the linearity and reversibility of printed flexible temperature sensors and support integration with wearable wireless monitoring systems.