Abstract
Flexible piezoresistive strain sensors with both high sensitivity and broad operational ranges are essential for advanced human-machine interfaces, wearable healthcare monitoring, and soft robotics. However, simultaneous optimization of sensitivity and strain range remains challenging due to the structural limitations of conventional solid conductive polymer composites. Herein, we report a direct ink writing (DIW) 3D printing strategy to fabricate printable MXene (Ti3C2Tx)/waterborne polyurethane (WPU) conductive elastomer composites featuring a hierarchical porous architecture. By incorporating sacrificial poly(methyl methacrylate) (PMMA) microspheres into a shear-thinning MXene/WPU ink, followed by thermal curing and selective solvent leaching, a multi-scale porous matrix consisting of interconnected macro-cavities and micro-porous cell walls is constructed. The engineered hierarchical porous sensor demonstrates a high Gauge Factor (GF = 184.2 in the 0–15% strain regime and GF = 52.6 up to 70% strain), a low detection limit of 0.05% strain, a rapid response time of 42 ms, and outstanding cyclic durability over 5,000 loading-unloading cycles. The superior piezoresistive performance originates from the strain-induced micro-contact deformation and reversible sliding of delaminated MXene nanosheets within the porous elastomeric matrix. Furthermore, the printed sensor array exhibits spatial tactile mapping capability and reliably detects micro-physiological signals such as arterial pulses and vocal cord vibrations. This work provides a scalable approach for manufacturing customizable, high-performance elastomeric piezoresistive sensors for next-generation flexible electronics.
