Stretching-Orientation Reinforced Double Network Solvent-Free Eutectic Gels for Ultrarobust, Flexible Human-Machine Interaction Devices

Abstract

Conductive gels hold promise for human-machine interaction (HMI) devices but face limitations in brittleness, solvent reliance, and fatigue resistance. These challenges are addressed by designing a solvent-free, stretch-oriented double-network eutectogel integrating high-molecular-weight polyacrylamide (structural reinforcement) with a dynamic poly(acrylic acid)/choline chloride deep eutectic network (ionic conductivity). Synergistic effects between molecular chain entanglements and stretch-induced alignment enhance mechanical robustness and energy dissipation, achieving tensile strength of 30.70 MPa, elongation of 703%, and record-high toughness of 133.86 MJ m⁻³ (surpassing reported eutectogels). Crucially, the aligned microstructure preserves conductive pathways, enabling multimodal sensing with high sensitivity (GF = 1.4 at 250% strain; TCR = 14.7% °C⁻¹) and stability (>300 cycles, without abrupt signal drift). Solution-based processing compatibility facilitates scalable fabrication of ultrathin coatings and printed patterns, demonstrated in functional HMI devices: a somatosensory glove (joint motion accuracy, latency <17 ms), and capacitive touchscreens (latency <34 ms), and temperature sensors (high thermal resolution). By resolving the strength-flexibility paradox, this work provides a platform for wearable HMI systems requiring transparency, ultrahigh strength, intrinsic flexibility, and environmental adaptability.