A waste cooling patch-derived flexible triboelectric sensor for wearable motion and throat vibration monitoring

Waste cooling patches are difficult to recycle through conventional processes because of their multilayer structure consisting of polymer gel, non-woven fabric, and plastic films. Instead of treating this multilayer structure as a recycling obstacle, this work reuses it as functional components for a flexible triboelectric sensor. A single-electrode triboelectric sensor, named the LY-sensor, was fabricated using the gel/non-woven layer as the negative triboelectric layer, the polyethylene film as the spacer, and conductive cloth as both the positive triboelectric layer and electrode. The naturally rough and porous gel surface provided a microstructured contact interface, which was beneficial for triboelectric sensing without additional surface modification. Under an applied force of 3–30 N at 1 Hz, the output voltage increased from 5.03 to 23.73 V, while the current increased from 0.06 to 0.145 μA. The voltage response showed a segmented linear relationship with force, with sensitivities of 0.896 V N−1 below 18 N and 0.279 V N−1 above 18 N. The optimized spacer height was 0.5 mm, and stable output was maintained after 10 000 cycles. The sensor was further used for distinguishing human motions and monitoring throat vibration signals. This work provides a simple strategy for converting waste cooling patches into low-cost wearable triboelectric sensors.