Additively Manufactured 3D Auxetic Metamaterials for Structurally Guided Capacitive and Resistive Tactile Sensing

Auxetic mechanical metamaterials (AMMs) with negative Poisson's ratio behavior offer an effective strategy for improving tactile sensor performance by enabling inward contraction and localized strain concentration under compression. This study presents a 3D AMM-based tactile sensing platform based on a cubic lattice with spherical voids, fabricated via digital light processing. The structure exhibits auxetic deformation under compressive loading, with inward collapse of ligaments confirmed through simulations and experimental analyses. Two sensor configurations are implemented, namely, a capacitive sensor that responds to pressure by modulating electrode spacing and dielectric distribution, and a resistive sensor based on a conformally coated network of carbon nanotubes that alters resistance under load. Electromechanical measurements confirm enhanced sensitivity compared to sensors based on conventional porous geometries with positive Poisson's ratio. The platform also maintains reliable operation over repeated cyclic loading. Its practical functionality is demonstrated through two representative applications—a 4 × 4 tactile array for spatial pressure mapping and object classification and a wearable insole system capable of monitoring gait patterns and detecting pronation types. The study findings validate the potential of architected auxetic structures as a scalable and versatile foundation for next-generation tactile sensing platforms.