Design, fabrication, and modeling of a polypyrrole-coated TPMS-based piezoresistive sensor

Official URL: https://dx.doi.org/10.1016/j.sna.2025.117140

Flexible pressure sensors have gained significant attention in electronic skin and wearable health monitoring systems, where flexibility, high sensitivity, and a broad sensing range are critical. Piezoresistive (PR) sensors are particularly advantageous due to their structural simplicity, cost-efficiency, stability, and scalability. The performance of PR sensors is predominantly governed by substrate geometry and material composition. In particular, porous architectures combined with conductive coatings have demonstrated enhanced sensitivity. This study presents the design and fabrication of a flexible PR sensor based on a triply periodic minimal surface (TPMS) architecture. The sensor was fabricated through a two-step process: first, a sacrificial mold was 3D printed using polyvinyl alcohol (PVA), followed by polydimethylsiloxane (PDMS) casting to obtain the porous structure. The resulting TPMS sensor was subsequently coated with polypyrrole (PPy) via vapor phase polymerization (VPP) of the pyrrole, enabling a uniform and conformal conductive layer. Micro-computed tomography (Micro-CT) analysis confirmed successful formation of the TPMS geometry and an interconnected porous network. The mechanical and electrical property of the sensor was evaluated simultaneously both experimentally and numerically. The performance of PR sensor was simulated by finite element analysis (FEA) using a Mooney–Rivlin hyperelastic material model. The fabricated sensors exhibited a high sensitivity of up to 23 within a compressive strain range of 0.1%–3% corresponding to low-pressure regimes relevant to biomedical applications. The PR sensor demonstrated robust performance under pressures around 35 mmHg, which aligns with thresholds associated with pressure ulcer formation. This work demonstrates that integrating TPMS-based architectures with conformal PPy coatings via VPP provides a promising strategy for developing flexible, high-performance piezoresistive sensors for continuous health monitoring and early detection of pressure-induced injuries.