Here the authors present an active thermal control system using 4D printed shape memory polymers and demonstrate how distinct deformation mechanisms lead to unique, tunable thermal properties using stretching- and bending-dominated architectures. Infrared thermography measurements with varying temperature and compression settings show that at low strains, radiation drives the effective conductance increase as the view factors among the struts increase with increasing strain, and at higher strains, conduction drives the effective conductance increase as the strut-to-strut contact areas increase. The effective thermal conductance increases from 4.41mW/K to 14.52mW/K and from 3.23mW/K to 10.48mW/K for the Kelvin foam and octet-truss microlattices, respectively, as strain increases from 0% to approximately 70%. As the strain is adjusted, the stretching-dominated octet-truss architecture exhibits abrupt changes in shape and conductance due to buckling. The bending-dominated Kelvin foam architecture allows for gradual geometric changes and precise tuning of thermal conductance. These findings provide a new understanding of thermal transport phenomena in 4D-printed metamaterials, which may be a breakthrough in tunable thermal systems.

 Mechanical metamaterials are attracting considerable attention due to theirunique properties not found in natural materials. Advanced geometrical shapessuch as Menger cubes, origami templates, and gyroids offer exciting avenues fordevice 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-printedgyroid structure with a conformal coating of carbon nanotubes (CNTs) is pre-sented. 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 gyroidstructure, 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 humanstance and motion monitoring.