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A manufacturing process with the capability to integrate electronics into 3D structures is of great importance to the development of next-generation miniaturised devices. In this study, Selective Laser Melting (SLM) was used to process copper/high-density-polyethylene (HDPE) powder mixtures to build conductive tracks in a 3D circuit system. The effects of copper/HDPE volume ratio, laser input power and scanning speed on the resistivity of CO2 laser processed tracks were investigated. The resistivity of the tracks decreased from 26.6 ± 0.6 × 10−4 Ωcm to 1.9 ± 0.1 × 10−4 Ωcm as the copper volume ratio increased from 30% to 60%. However, further increasing the copper ratio to 100% resulted in poor conductivity. The lowest resistivity was achieved with an input power of 20 W and scanning speed of 80 mm/s. Additionally, processing using single-track-scanning and raster-scanning programs was compared; the overall energy distribution on the surface was more uniform using a raster-scanning program, which further reduced the resistivity to 0.35 ± 0.04 × 10−4 Ωcm. Based on the results, a 3D multi-layered circuit system was manufactured with the HDPE as the substrate/matrix material and copper/HDPE mixture as the conductive-track material. This circuit system was successfully manufactured, demonstrating the possibility of using SLM technology to manufacture dissimilar materials towards 3D electronic applications.

Acrylonitrile butadiene styrene (ABS) specimens fabricated by fused filament fabrication (FFF) were post treated by acetone, ethyl acetate and their mixed vapour. The effect of different chemical vapour, exposure time and building orientation on the surface roughness, tensile strength, dimension and weight stability of the ABS specimens were investigated before and after treatment. The results demonstrated that all chemical vapours were capable of improving the surface coarseness of ABS specimens. The tensile strength of specimens treated with the acetone or the mixed vapour decreased with increasing the exposure time. Surprisingly, it did not change for specimens treated with the ethyl acetate vapour when the exposure time reached 30 min. The deviations of length and width of specimens after chemical vapour treatment were lower than 5 %, irrespective of the building orientations. However, the deviations of thickness were high (up to 25 %). The weight of specimens after treatment increased with prolonging the exposure time due to the absorption of the chemical vapours.

The correlation between MWCNT aspect ratio and the quasi-static and dynamic mechanical properties of composites of MWCNTs and PMMA was studied for relatively long MWCNT lengths, in the range 0.3 mm to 5 mm (aspect ratios up to 5 × 105) and at low loading (0.15 wt%). The height of the MWCNTs prepared were modulated by controlling the amount of water vapour introduced in the reactor limiting Ostwald ripening of the catalyst, the formation of amorphous carbon and any increase in CNT diameter. The Tg of PMMA increased by up to 4 °C on addition of the longest tubes as they have the ability to form physical junctions with the polymer chains which lead to enhanced PMMA-MWCNTs interactions and increased mechanical properties, Young's modulus by 20% on addition of 5 mm long MWCNTs. Predictions of the Young's modulus of the composites of PMMA and MWCNT with the Mori-Tanaka theory show that future micromechanical models should account for MWCNT agglomeration and polymer-nanotube interactions as a function of CNT length.