Additively Manufactured Mechanical Metamaterial-Based Pressure Sensor with Tunable Sensing Properties for Stance and Motion Analysis

Abstract

Mechanical metamaterials are attracting considerable attention due to their unique properties not found in natural materials. Advanced geometrical shapes such as Menger cubes, origami templates, and gyroids offer exciting avenues for device engineering. In addition, the recent developments of various additive manufacturing technologies have expanded materials selection and geometrical complexities. Herein, a piezoresistive pressure sensor based on a 3D-printed gyroid structure with a conformal coating of carbon nanotubes (CNTs) is presented. The gyroid structures are printed using fused deposition modeling (FDM) 3D printing with thermoplastic polyurethane (TPU), providing mechanical robustness even at low densities. By altering the relative density of the gyroid structure, Young's modulus can be tailored, ranging from 0.32 MPa at 30% relative density and 3.61 MPa at 80% relative density. The presented gyroid-based pressure sensor achieves a wide sensing range of up to 1.45 MPa and a high sensitivity of 2.68 MPa-1. The sensor is integrated into a shoe for wearable applications, demonstrating its mechanical robustness and potential for human stance and motion monitoring.