Three-Dimensional Printing of Abrasive, Hard, and Thermally Conductive Synthetic Microdiamond-Polymer Composite Using Low-Cost Fused Deposition Modeling Printer Sidra Waheed, †,‡ Joan M. Cabot, †,‡ Petr Smejkal, ‡ Syamak Farajikhah, § Sepidar Sayyar, § Peter C. Innis, § Stephen Beirne, § Grant Barnsley, § Trevor W. Lewis, † Michael C. Breadmore, †,‡ and Brett Paull* ,†,‡ † ARC Centre of Excellence for Electromaterials Science (ACES), School of Natural Sciences, Faculty of Science, Engineering and Technology and ‡ Australian Centre for Research on Separation Science (ACROSS), School of Natural Sciences, Faculty of Science, Engineering and Technology, University of Tasmania, Hobart 7001, Australia § ARC Centre of Excellence for Electromaterials Science (ACES), AIIM Facility, Innovation Campus, University of Wollongong, Wollongong, NSW 2500, Australia * S Supporting Information ABSTRACT: A relative lack of printable materials with tailored functional properties limits the applicability of three-dimensional (3D) printing. In this work, a diamond-acrylonitrile butadiene styrene (ABS) composite filament for use in 3D printing was created through incorporation of high-pressure and high- temperature (HPHT) synthetic microdiamonds as a filler. Homogenously distributed diamond composite filaments, containing either 37.5 or 60 wt % microdiamonds, were formed through preblending the diamond powder with ABS, followed by subsequent multiple fiber extrusions. The thermal conductivity of the ABS base material increased from 0.17 to 0.94 W/(m·K), more than five- fold following incorporation of the microdiamonds. The elastic modulus for the 60 wt % microdiamond containing composite material increased by 41.9% with respect to pure ABS, from 1050 to 1490 MPa. The hydrophilicity also increased by 32%. A low-cost fused deposition modeling printer was customized to handle the highly abrasive composite filament by replacing the conventional (stainless-steel) filament feeding gear with a harder titanium gear. To demonstrate improved thermal performance of 3D printed devices using the new composite filament, a number of composite heat sinks were printed and characterized. Heat dissipation measurements demonstrated that 3D printed heat sinks containing 60 wt % diamond increased the thermal dissipation by 42%. KEYWORDS: 3D printing, fused deposition modeling, composite, microdiamonds, thermal conductivity, heat sinks, hydrophilicity, recyclable 1. INTRODUCTION Additive manufacturing, commonly referred to as 3D printing (3DP), has emerged as a powerful and dynamic technology to produce a wide range of complex structures/components, already enabling rapid prototyping and beginning to impact industrial production significantly. 1-4 3DP can provide a route to the rapid production of highly customized structures, tailored toward specific applications, while simultaneously reducing the cost and time associated with traditional subtractive fabrication techniques. 5,6 Among all of the 3DP technologies, fused deposition modeling (FDM) is currently the most commonly applied print technology, essentially due to its simplicity and low cost, together with the availability of a wide variety of base print materials. 7-9 Polymer FDM printing involves the forced extrusion of a thermoplastic filament through a pinch roller mechanism into a heated nozzle, which is capable of three- directional movement. This movement allows the nozzle to build a 3D structure in a layer-by-layer process. 10 Acrylonitrile butadiene styrene (ABS) is one of the most commonly used thermoplastic polymer filaments in FDM printing. ABS has a relatively low glass-transition temperature with excellent processability. Additionally, the noncrystalline nature of ABS reduces its shrinkage ratio during the cooling process and enables high-precision printing and dimensional stability. 11 However, ABS has no specific functional advantages per se and has an intrinsically low thermal conductivity, which hinders its use in many applications, including high-powered miniaturized electronic devices. 12 Received: October 18, 2018 Accepted: January 9, 2019 Published: January 9, 2019 Research Article www.acsami.org Cite This: ACS Appl. Mater. Interfaces 2019, 11, 4353-4363 © 2019 American Chemical Society 4353 DOI: 10.1021/acsami.8b18232 ACS Appl. Mater. Interfaces 2019, 11, 4353-4363 Downloaded by TSINGHUA UNIV at 02:19:40:635 on July 01, 2019 from https://pubs.acs.org/doi/10.1021/acsami.8b18232.