(202b) Direct Printing of Epoxy-Graphite Composite Ink for Thermal Management Devices

The project focuses on developing composite inks composed of a low viscosity Epoxy (EPON 862), graphite nanoplatelet and fillers such as carbon fibers, nanotubes and nanowires for use in thermal management devices. The viscoelastic properties are tuned by filler concentrations – graphite and carbon fiber concentrations. By combining these functional materials 3D structures with a high thermal conductivity (~ 2 W/mK), high elastic modulus (> 1000MPa) and high electrical conductivity are achieved. Of particular focus is the relationship of rheological properties with final printed performance. The optimal graphite concentration in relation to the percolation threshold of graphite in the epoxy is determined and properties (thermal and electrical conductivity) measured as a function of graphite concentration. It is found out that the rheological percolation does not necessarily correspond to electrical percolation and a higher concentration is needed to achieve optimal properties. The results show that by carefully tailoring functional properties of the ink, net-shape multifunctional structures can be directly printed for thermal management device applications, such as heat sinks