Constructing Anisotropic Conductive Networks inside Hollow Elastic Fiber with High Sensitivity and Wide-Range Linearity by Cryo-spun Drying Strategy

Stretchable conductive fibers composed of conductive materials and elastic substrates have advantages such as braiding ability, electrical conductivity, and high resilience, making them ideal materials for fibrous wearable strain sensors. However, the weak interface between the conductive materials and elastic substrates restricts fibers flexibility under strain, leading to challenges in achieving both linearity and sensitivity of the as-prepared fibrous strain sensor. Herein, cryo-spun drying strategy is proposed to fabricate the thermoplastic polyurethane (TPU) fiber with anisotropic conductive networks (ACN@TPU fiber). Benefiting from the excellent mechanical properties of TPU, and the excellent interface among TPU, silver nanoparticles (AgNPs) and polyvinyl alcohol (PVA), the prepared ACN@TPU fiber exhibits an outstanding mechanical performance. The anisotropic conductive networks enable the ACN@TPU fiber to achieve high sensitivity (gauge factor, \(GF\) $\mathit{GF}$  = 4.68) and excellent linearity within a wide working range (100% strain). Furthermore, mathematical model based on AgNPs is established and the resistance calculation equation is derived, with a highly matched fitting and experimental results ( \(R^{2}\) $R^2$  = 0.998). As a conceptual demonstration, the ACN@TPU fiber sensor is worn on a mannequin to accurately and instantly detect movements. Therefore, the successful construction of ACN@TPU fiber with anisotropic conductive networks through the cryo-spun drying strategy provides a feasible approach for the design and preparation of fibrous strain sensing materials with high linearity and high sensitivity.