A flexible multimodal piezoresistive sensor for wearable health monitoring and thermal management: integrating high-strain sensing, sound detection, and photothermal conversion

The increasing demand for multifunctional wearable devices has sparked concerns in developing multifunctional wearable materials with flexibility, pressure resistance, and effective thermal management to address health monitoring and thermal regulation challenges in demanding environments. In this work, a novel multifunctional piezoresistive sensor, melamine foam/PPy/MXene (KMPM), has been developed, integrating high-strain sensing, health monitoring, sound detection, and photothermal conversion capabilities. It was fabricated via a simple chemical oxidation method and cost-effectively solution-dip-coating technique to deposit polypyrrole (PPy) and MXene onto melamine foam (MF). The KMPM sensor demonstrated a wide detection range (5–21 kPa), high sensitivity (S = 1.81 kPa⁻¹), fast response times (165 ms for response, 150 ms for recovery), and exceptional stability (over 3000 cycles). Beyond conventional human motion sensing, it can be used to detect both biological and abiotic sound signals. Notably, KMPM exhibited rapid photothermal responses, reaching temperatures above 340 °C within 15 s when exposed to near-infrared (808 nm) radiation, and maintained a stable surface temperature and heating rate under repeated radiation cycles. It demonstrated the KMPM sensor opened opportunities for applications in thermal management, health monitoring, sound recognition, and wearable devices.