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 hightemperature (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 fivefold 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%.

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In this paper, we used computational fluid dynamics simulation (ANSYS CFX) to compare the performance of surfboard fins with grooves (and a bumpy-leading edge) to conventional surfboard fins. The simulations predicted the performance of each type of fins in terms of hydrodynamic forces and their behavior for angles of attack up to 45 degrees. Our results indicated that the pressure contours around fins with grooves (and bumpy-leading edge) were lower compared to pressure contours around conventional fins. The grooved fins exhibited a 13 ± 1% reduction in drag (coupled with a much smaller reduction in lift) at the stall angle, contributing to an overall 11 ± 1% improvement in the lift-to-drag ratio compared to conventional fins. Graphical abstract