Additive manufacturing of anisotropic graphene-based composites for thermal management applications

The use of additive manufacturing (AM) for the rapid, facile creation of complex structures could provide thermal management solutions in the form of heat sinks and heat exchangers with high surface areas that facilitate heat dissipation. To prepare a heat sink with high thermal conductivity (TC), we use vat photopolymerization (VPP) of a polymer-based composite material with a low TC that is enhanced by loading with a graphene-based thermally conductive filler. Phase separation of the carbon-based filler, in this case graphene nanoplatelets (GNP), in the monomer printing solution is prevented by stabilizing the GNPs by the addition of a second fiber-like clay (sepiolite) filler, which traps the GNPs. This methodology enables the AM of a composite with a relatively high GNP concentration of 2.0 wt %, yielding a TC increase of 160 % vs. the pristine polymer—an impressive accomplishment for VPP 3D printing. Moreover, this printing technique yields a material with anisotropic TC with a cross-plane/in-plane (TC┴/TC=) ratio of 1.6, which is beneficial for thermal management systems required to dissipate the heat vertically from a heat source. Such VPP 3D-printed composites with high and anisotropic TC could be applied in thermal management systems made of lightweight and cost-effective materials.