Auxetic mechanical metamaterials for resistive tactile sensors: a review

Resistive tactile sensors are crucial components in emerging technologies such as robotics, prosthetics, and wearable systems. However, their performance is often fundamentally limited by the positive Poisson's ratio of their conventional structural materials. Auxetic mechanical metamaterials (AMMs), which exhibit a negative Poisson's ratio, offer a powerful geometry-driven solution to these limitations. By converting compressive load into inward contraction, AMM architectures amplify strain localization and densify internal conductive networks, thereby synergistically enhancing sensitivity, ensuring stable performance in confined environments, and minimizing physical crosstalk in sensor arrays. This review provides a comprehensive geometry-centered overview of recent advances in AMM-based resistive tactile sensors. First, the foundational principles of auxetic mechanics and resistive sensing are established to provide a theoretical basis for the discussion. The review subsequently surveys representative auxetic topologies, then examines the key fabrication strategies used to realize these complex architectures. Next, the structural designs of recent sensor implementations are analyzed to highlight how geometric configuration translates into enhanced electromechanical performance. Finally, current challenges and future prospects are discussed to provide a roadmap for future research. The analysis presented in this review establishes a coherent framework for understanding and leveraging AMMs to accelerate the development of next-generation high-performance tactile sensing systems.