Thermal conductivity of 3D-printed block-copolymer-inspired structures

• Demonstrating the utility of using 3D printing to study thermal conduction in heterogeneous structures. • Exploring the effect of phase contrast on effective thermal conductivity in heterogeneous structures. • Development of structure-specific models for predicting effective thermal conductivity . • Reporting a simple empirical model for co-continuous heat conduction through two phases that is independent of structure and demonstrates that effective thermal conductivity is preponderantly dictated by volume fraction and component thermal conductivities . This study primarily focuses on examining the impact that geometric structure has on thermal conductivity of multi-phase constructs in different 3D-printed poly(lactic acid), PLA, samples. The investigated structures are inspired by morphologies formed by diblock copolymers: lamellae, hexagonally packed cylinders, and gyroid. This research also investigates how volume percentage and material combination influence the thermal conductivity of these structures. The samples can be tailored to simulate various thermal management structures observed in practical applications, such as thermal interface materials in electronic devices. Thermal conductivity ratio is controlled using air, the least conductive material at 0.026 W/(m K), PLA at 0.136 W/(m K), and thermal paste at 5.11 W/(m K). Different models were tested against thermal conductivity measurements in order to capture the effect of material type (PLA-Air versus PLA-Thermal Paste), volume percentage, structure, and orientation. Simple, effective medium models were good predictions of thermal conductivity in lamellar structures, but it was necessary to develop models for conduction through cylindrical and gyroid structures. Finally, all results were normalized to find a universal model that is independent of structure and material. This approach provides a simple method to predict how to reduce or enhance transport properties and heat management capabilities of 3D printed objects.