Electrically Conductive 3D-Printed Piezoresistive Metastructure Lattice Sensors

The growing demand for advanced, personalized wearable health monitoring technologies has driven the development of innovative fabrication methods for flexible electronics. Here, we present electrically conductive 3D-printed piezoresistive metastructure lattice sensors combining structural programmability with tunable electromechanical performance. Leveraging high-resolution stereolithography, metastructure lattices are fabricated with microscale precision, offering design freedom to orthogonally tune mechanical stiffness and deformation through microstructural design. Piezoresistive functionality is imparted via two complementary coating strategies─titanium carbide (TiC) ink dip coating and oxidative chemical vapor deposition (oCVD) of doped polypyrrole (PPy), representing contrasting wet and dry processing routes. These coatings yield distinct interfacial architectures and sensing mechanisms: microcrack-mediated piezoresistivity in TiC-coated lattices and continuous, positive piezoresistivity in conformal oCVD PPy coatings. Both versions achieved good gauge factors (12–13), broad detection ranges (up to 180 N), and excellent cyclic repeatability under both low (0.2 N) and high (90 N) cyclic compressive forces (<5% variation in output). The applicability of these sensors was demonstrated through real-time human gait monitoring with monolithically integrated shoe insoles, underscoring their potential in wearable technology. This study highlights the effectiveness of combining advanced manufacturing techniques with conductive coatings to develop mechanically robust and sensorized wearable devices for applications in healthcare and rehabilitation.