This article reports on the use of the Neumann triangle method combined with a focused ion beam sample preparation technique and atomic force microscopy (NT-FIB-AFM) to measure interfacial tension ratios in partially wetted ternary and quaternary immiscible polymer blends prepared by melt processing. It is shown that PS/PP/HDPE, PS/PCL/PP, PLLA/PCL/PS, PMMA/PS/PP, and a quaternary blend system comprised of HDPE/PP/PS/PMMA all display a partial wetting morphology with a three-phase line of contact and that the interfacial tension ratios obtained by the NT-FIB-AFM approach compare well with results obtained by the classical breaking thread method. The HDPE/PP/PS/PMMA quaternary blend, in particular, is quite unique and displays a partial wetting morphology with spectacular PS/PMMA composite droplets located at the HDPE/PP interface. Furthermore, all of the above data generated for the ternary and quaternary systems also satisfy the Laplace equation. When 1% of an SEB diblock copolymer is added to the PS/PP/HDPE system, the Neumann triangle method reveals that the PS/HDPE interfacial tension decreases from 4.2 ( 0.6 to 3.3 ( 0.4 mN/m, with an estimated apparent areal density of 0.19 ( 0.07 molecule/nm 2 of copolymer at the PS/HDPE interface. The results presented in this paper show that it is possible to generate complex morphologies demonstrating partial wetting for a wide range of polymer blend systems with a relatively simple experimental approach. Furthermore, it allows the measurement of the interfacial tension ratios of a matrix-dispersed phase blend system examined in situ after melt processing. The apparent areal density of a copolymer interfacial modifier can also be estimated. This is an important result, since it is still a challenge to measure the variation of the interfacial tension as a function of the copolymer areal density in multiphase polymer blends.

Direct ink writing (DIW) combined with post-deposition thermal treatments is a safe, cheap, and accessible additive manufacturing (AM) method for the creation of metallic structures. Single-material DIW enables the creation of complex metallic 3D structures featuring overhangs, lengthy bridges, or enclosed hollows, but requires the printing supporting structures. However, the support printed from the same material becomes inseparable from the building structure after the thermal treatment. Here, a multi-material DIW method is developed to fabricate complex three-dimensional (3D) steel structures by creating a removable support printed from a lower melting temperature metal (i.e., copper) or a ceramic (i.e., alumina). The lower melting temperature metal completely infiltrates the porous steel structures for a hybrid configuration, while the ceramic offers a brittle support that can be easily removed. The influence of the support materials on the steel structure properties is investigated by characterizing the dimensional shrinkage, surface roughness, filament porosity, electrical conductivity, and tensile properties. The hybrid configuration (i.e., copper infiltrated steel structures) improves the electrical conductivity of the fabricated steel structure by 400% and the mechanical stiffness by 34%. The alumina support is physically and chemically stable during the thermal treatment, bringing no significant contamination to the steel structure.

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