Intrinsic piezoresistive mechanism of conductive porous nano composites with linearity assumption: Theory and experimental analysis

Abstract

Porous piezoresistive nanocomposites (PPNs) are pivotal for advanced flexible sensors due to their unique combination of compressibility, low density, and breathability. However, their rational design is hindered by a fundamental disconnect: existing models either treat mechanical deformation (e.g., pore collapse) and electrical conduction (e.g., tunneling) in isolation, or rely on empirical parameters lacking clear physical links to microstructure. This gap obscures the intrinsic piezoresistive mechanism, particularly the dominant role of ligament bending (rather than pore closure) in governing resistance changes under small-to-moderate strains. Herein, we propose a theoretical model that directly couples the micromechanics of porous structures with the evolution of their conductive network. By integrating Timoshenko beam theory (for ligament bending/stretching) with quantum tunneling theory within a periodic Gibson-Ashby unit cell, our model quantifies piezoresistive response through key microstructural and electrical parameters. Experimental validation of the proposed model was conducted by measuring the piezoresistive behaviors of different types of PPNs. Furthermore, we extend this framework by incorporating viscoelasticity (Kelvin-Voigt model) to accurately capture time-dependent relaxation behaviors—a critical feature for dynamic sensing. Transcending phenomenological fitting, this work provides a predictive and generalizable toolset for the physics-guided, microstructure-informed design of high-performance PPN sensors.