Tactile sensors are widely used in robotics, prosthetics, wearable devices, and healthcare monitoring, converting external stimuli like pressure and force into electrical signals. Scientists have worked to improve their sensing range and sensitivity, but existing auxetic mechanical metamaterials face fabrication and integration challenges. A breakthrough metamaterial technology now addresses these gaps, paving the way for next-generation wearable devices and health monitoring.

A team of researchers from Seoul National University of Science and Technology (SeoulTech, Seoul, South Korea) has developed a 3D-printed auxetic metamaterial-based tactile sensing platform. Built on a cubic lattice with spherical voids, the platform was fabricated using digital light processing 3D printing. The design leverages auxetic mechanical metamaterials with a negative Poisson’s ratio, enabling inward contraction and localized strain concentration upon compression.

The sensors were tested in both capacitive and piezoresistive modes. In the capacitive mode, pressure altered electrode spacing and dielectric distribution, while in the piezoresistive mode, a carbon nanotube network changed resistance under load. The findings, published in Advanced Functional Materials, highlighted that this approach enhanced sensitivity, improved performance stability in confined spaces, and minimized crosstalk between sensing units.

The team demonstrated two proof-of-concept applications: a tactile array for spatial pressure mapping and a wearable insole system for gait pattern monitoring and pronation detection. The platform is also suitable for robotic hands requiring precision and wearable health monitoring systems. Looking ahead, auxetic-structured sensors could support rehabilitation devices, human-robot interfaces, and personalized medicine through custom-fit monitoring systems.

“The proposed sensor platform can be integrated into smart insoles for gait monitoring and pronation analysis, robotic hands for precise object manipulation, and wearable health monitoring systems that require comfortable sensing without disrupting daily life,” said Dr. Soonjae Pyo, Associate Professor at SeoulTech. “Importantly, the auxetic structure preserves its sensitivity and stability even when confined within rigid housings, such as insole layers, where conventional porous lattices typically lose performance. Its scalability and compatibility with various transduction modes also make it suitable for pressure mapping surfaces, rehabilitation devices, and human-robot interaction interfaces that require high sensitivity and mechanical robustness.”

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