MXene-POLYURETHANE COMPOSITES AS WEARABLE STRAIN SENSORS FOR FINGER MOTION AND ON-SURFACE WRITING

Abstract

The remarkable applications of flexible and wearable sensors in human motion detection and health monitoring have attracted considerable attention from both academic and industrial communities. Wearable strain sensors for finger-motion monitoring demand materials that combine high conductivity, flexibility, long-term durability, fast response, and stable interfaces. Here we report a MXene–polyurethane (PU) platform built on an MDI/HBP/PDMS network with 50 wt% soft segments (PU-50) that serves as a biocompatible, elastic substrate for a Ti₃C₂Tₓ conductive layer. MXene-PU composites were characterized by scanning electron microscopy (SEM), tensile testing and electrical measurements. SEM confirms the intended morphologies: layered, lamellar MXene stacks that form percolating pathways and a PU microphase-separated morphology between soft and hard segments. Three device variants were evaluated under finger flexion with increasing frequency: MXene on neat PU, PU with 1 wt% pure MXene in the bulk (PUMX), and PU with 1 wt% functionalized MXene (PEG-MXene) in the bulk (PUMP). Time-resolved resistance measurements acquired every 20 ms yielded clear, low-hysteresis ΔR/R₀ waveforms across all frequencies, with a consistent performance hierarchy in which PUMP exhibited the lowest baseline drift and the most stable cycle-to-cycle response, while the neat PU device displayed the largest resistance modulation amplitude. On-surface drawing tests on the neat-PU-MXene sensor further demonstrated pattern-robust sensitivity, producing distinct, repeatable temporal signatures for triangle, circle, and square trajectories with rapid baseline recovery and minor residual offsets. The obtained results validate MXene–PU as a fast, stable, and comfortable candidate for wearable finger motion sensors. They also identify mild interface optimization—via functionalized MXene in the substrate—as an effective way to enhance signal stability and suppress baseline drift while preserving signal fidelity across frequencies. This motivates future work on long-term stability, environmental compensation, and integration with compact wireless readout for multi-gesture recognition.
Keywords: MXene, polyurethanes, tensile testing, wearable sensors, finger-motion sensing.