Tunable thermal transport in 4D printed mechanical metamaterials

Abstract

Here the authors present an active thermal control system using 4Dprinted 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.