Integrated Self-Powered Sensors for Continuous Foot Health Monitoring via Laser-Induced MXene-Composited Graphene Hybrids From Lignocellulose

Abstract

Intelligent wearable devices based on laser-induced graphene (LIG) have attracted significant attention for human health monitoring. This paper proposed an innovative all-in-one design for preparing a self-powered smart insole using laser-induced MXene-composited graphene hybrid (LIG@MXene) from lignocellulose precursor. By incorporating MXene into the LIG, the composite achieved improved crystallinity and reduced defects, contributing to the electrical conductivity (17.2 Ω∙sq−1) and structural stability. The optimal laser processing parameters are 55% for laser power and 70 mm s−1 for etching rate. The optimized LIG@MXene composite functions as a versatile platform for integrating triboelectric nanogenerator (TENG) with a high output power of 35 V cm−2, supercapacitor with a superior areal capacitance of 71.4 mF cm−2 and the excellent cycling stability of 89.5% retention, Joule heater of the maximum heating temperature of 113 °C at 5 V, and various flexible sensors for pressure, humidity and sweat composition with high sensitivity and linearity. In particular, the minimum L-tyrosine limit of detection in sweat is only 9.60 µM. These functional modules are embedded within an insole via a direct laser writing technology, which only emitted 9.10 kg CO2 eq during manufacturing. The direct laser-patterned synthesis of LIG@MXene composite represents a significant step forward in advancing smart wearable electronic devices.