Wearable Strain Sensors via Tough and Conductive Hydrogel-Based MoS ₂ Composites for Real-Time Motion Tracking

Wearable and flexible sensors, capable of transducing mechanical stimuli into electrical signals, have attracted significant attention for applications, such as human motion tracking, physiological monitoring, soft robotics, electronic skin, and human-machine interfaces. In this work, we develop a polyacrylamide (PAAm)-based hybrid composite integrated with a conductive hydrogel to simultaneously enhance mechanical robustness and electrical performance for real-time motion sensing. The composite features a double-network hydrogel (DNH) composed of PAAm and sodium alginate, reinforced with MoS₂ nanosheets and ethylene glycol-doped PEDOT:PSS (DNH/MoS₂NS/EG-PEDOT:PSS), yielding a highly stretchable, adhesive, and conductive material. The adhesive layer exhibits excellent mechanical properties, including a maximum strain of over 500% and a peeling force of approximately 25 N/m, while the conductive layer maintains over 300% stretchability with significantly improved electrical conductivity. The strain sensor demonstrates a gauge factor (GF) of approximately 1.67 with excellent linearity (R ² ≈ 0.97), along with stable signal response over 10,000 loading/unloading cycles with minimal hysteresis. Real-time motion sensing experiments on human joints and neck movements show high fidelity, stable electrical signals, enabling the detection of subtle motions, such as speech. These results underscore the composite's strong potential for next-generation wearable sensors in healthcare monitoring, rehabilitation, and human-computer interaction systems.