Flexible and Tunable Piezoresistive Sensors Based on Graphite-Loaded CTBN-Toughened Epoxy Composites

Flexible piezoresistive sensors are essential for emerging wearable electronics, yet existing polymer matrices present inherent trade-offs between mechanical rigidity, signal drift, and long-term reliability. In this work, we develop screen-printed pressure sensors based on graphite-loaded, CTBN-toughened epoxy composites that simultaneously achieve high sensitivity, low creep, and robust cyclic stability. Graphite provides a percolated conduction network governed by tunneling transport, while CTBN reactive rubber introduces localized stress-relief domains that enhance fracture toughness without severely interrupting electrical pathways. Systematic tuning of graphite content (2-12 wt %) allowed tunability in sensitivity, baseline resistance, and dynamic range. CTBN loading from 0-10 wt % established an optimal composition of 4 wt % that minimizes resistance drift, preserves fast electromechanical recovery, and provides stable thermal response in the range of -20 to 80 °C. The fabricated sensors show high piezoresistive response with low hysteresis, <±5% drift after 1000 pressure cycles, broad operating range, and high uniformity. This pressure sensor array shows excellent flexibility and is suitable for wearable health monitoring. This work demonstrates a scalable approach to flexible, tunable, and durable piezoresistive sensors, offering potential for applications in wearable electronics.