Fibrous Pressure Sensor with Unique Resistance Increase under Partial Compression: Coaxial Wet-Spun TiO₂/Graphene/Thermoplastic Polyurethane Multi-Wall Multifunctional Fiber.

Abstract

Fiber-shaped resistive pressure-sensitive sensors are rare. Although fibers are widely used in strain sensors owing to their structural advantages, developing fiber-shaped resistive pressure sensors is challenging. This challenge arises because the fiber acts as a series circuit along its axis, requiring increased resistance in the compressed region for a significant signal. Coaxial wet-spinning is used to create a multi-walled fiber. The outer layer, made of thermoplastic polyurethane (TPU)/TiO₂ slurry, ensured a smooth surface, while the inner core, containing 4% graphene nanoplatelets (GNPs), is extruded at 20 mL h^-1. Unlike conventional resistance-increasing pressure sensors, TGTMW fiber shows rising resistance under compression due to microcracks in its multi-wall structure. Its pressure sensitivity is evaluated using various 3D-printed indenters and showcasing its excellent performance. This sensor has found promising applications in remote motion detection, press or slide differentiation through wavelet transforms applied to high-speed sensing data, and real-time signal acquisition from a multi-channel sensing array. Additionally, intuitive visualization software is developed for the sensing array application and implemented a CNN-based machine learning algorithm for data analysis. The system achieved a recognition accuracy of ≈99.6% for 12 different compression modes. This work is believed to propose a new mechanism and design for fiber-based pressure sensors.