writer：Guicen Liu, Long Jin, Yong Ao, Boling Lan, Tianpei Xu, Shenglong Wang, Tingting Zhou, Zihan Wang, Wei Zhao, Zhiyuan Gao, Weili Deng, Weiqing Yang
keywords：Negative Poisson''''''''s ratio structure，Piezoelectric sensors，Anisotropic strain sensing，PVDF-TrFE
source：期刊
Issue time：2026年

Yarn-based sensors offer excellent conformability for wearable electronics on complex body surfaces. Yet existing sensing mechanisms face a fundamental limitation: interface-dominated approaches suffer from signal stochas ticity and drift due to contact interface instability, while piezoelectric alternatives remain restricted to uniaxial responses incapable of discriminating coupled multi-axial deformations. Here, a geometry-engineered negative Poisson’s ratio piezoelectric yarn sensor is designed to integrate geometry-driven deformation with strain-induced piezoelectric polarization. The helical scaffold transforms axial stretching into radial expansion through structural rearrangement, which enables a single mechanical stimulus to generate distinguishable electrical responses along different axes. Upon axial stretching, the helical windings undergo coordinated rearrangement that converts the longitudinal extension into pronounced radial expansion, intrinsically coupling the longitudinal and transverse deformation pathways within the same fiber architecture. This geometry-driven strain redistribution yields a piezoelectric output of 5.10 V under 30% tensile strain, representing a 42-fold enhancement over conventional positive Poisson’s ratio yarns, with stable operation over 10,000 cycles. The resulting demonstrates effective monitoring of multi-axial deformations, including axial stretching, normal pressure, and bending gradients. As a proof of concept, the sensor enables closed-loop rehabilitation training feedback, establishing a geometry-driven strategy for wearable anisotropic biomechanical monitoring on com plex body surfaces