Breakthrough achieved in sensitive and wearable tactile sensors through 3D printing of auxetic design.

In a groundbreaking development, researchers at École Polytechnique Fédérale de Lausanne (EPFL) and the Seoul National University of Science and Technology have created a novel tactile sensing platform using auxetic mechanical metamaterials (AMMs). This innovative design promises breakthroughs in various fields, including smart insoles, robotics, and health monitoring.

Auxetic mechanical metamaterials are unique in their negative Poisson's ratio, a counterintuitive trait that makes them highly attractive for advanced sensing applications. Unlike conventional porous structures, the design of the new tactile sensing platform avoids lateral expansion, making it more wearable and less prone to interference.

The unique negative Poisson's ratio behavior of the auxetic metamaterials enables inward contraction under compression, which concentrates strain in the sensing region and boosts sensitivity. This feature is particularly beneficial in the piezoresistive sensing mode, where a carbon nanotube coating changes resistance under load. In the capacitive sensing mode, pressure alters electrode spacing and dielectric distribution.

The cubic lattice with spherical voids in the new tactile sensing platform further enables inward contraction and localized strain concentration when compressed. This design strengthens sensor performance in three ways: enhancing sensitivity through localized strain concentration, maintaining stability in confined structures, and minimizing crosstalk between sensing units.

The team validated the concept with two demonstrations: a tactile array for spatial pressure mapping and object classification, and a wearable insole system capable of monitoring gait patterns and detecting pronation types. The scalability and compatibility with multiple transduction modes make the platform suitable for pressure mapping surfaces, rehabilitation devices, and human-robot interaction interfaces that require high sensitivity and mechanical robustness.

The 3D-printing process used for fabricating the tactile sensing platform is based on digital light processing (DLP). This method allows for precise and intricate designs, making it ideal for the complex structure of the auxetic metamaterials.

The findings of this research have been published in the prestigious journal, Advanced Functional Materials. The development of this tactile sensing platform represents a significant step forward in the field of sensing technology, with potential applications ranging from everyday wearables to advanced robotics.

Breakthrough achieved in sensitive and wearable tactile sensors through 3D printing of auxetic design.