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This study aims to investigate surface roughness, microstructure, and mechanical properties of overhead thin-wall structures of stainless steel(SS316L) fabricated by cold metal transfer (CMT)-based wire + arc additive manufacturing (WAAM). In the first stage, single-layer bead experiments were carried out in flat and overhead positions utilizing Box-Behnken experimental design with a range of process parameters (i.e., wire feed rate, travel speed, and weave amplitude). To study the effect of individual process parameters on the bead geometry and identify a process window, analysis of variance(ANOVA) is performed using the bead cross-section measurement data. For single layer bead experiments in flat and overhead position, out of all process parameters, the weave amplitude is the most significant parameter on bead width, whereas travel speed is most significant parameter for bead height. Based on single-layer bead experiments, process parameters for thin wall deposition were identified. In the second stage, two thin-walls were deposited with wire feed rates of 1000 and 1500 mm/min in the overhead position. The surface roughness was measured using cloud point data acquired from the coordinate measuring machine(CMM). The deposited structure with the wire feed rate of 1500 mm/min resulted in better surface quality. It was also observed that, microstructure was composed of austenite and dendritic delta ferrite. The microstructure changed as the deposition height increased. The average microhardness value was measured 183 HV and 187.4 HV for the overhead structures. Average tensile properties of the SS316L overhead structures were comparable to that of SS316L fabricated by other WAAM processes. 

Evaporation patterns of liquid droplets containing nanoparticles or colloids have extensive applications in diagnostics and printing. Controlling these patterns by studying the evaporation behavior of colloidal droplets on surfaces is important for enhancing sensing platforms. In this study, A liquid‐repellent microcavity surface is introduced to robustly capture deposited analytic particles. The proposed microcavity surface maintains stable air pockets for liquid repellency and strong pinning for the spatial stabilization of the evaporating droplet, thereby resulting in a coffee‐ring concentration. This microcavity surface also acts as a “microcontainer” for the deposited particles, thereby protecting them against external damage. To demonstrate the multifaceted capabilities of microcavity surfaces, further comparison is done of three different surface structures, planar, micropillared, and that with microcavities in a hexagonal arrangement, by analyzing their evaporation dynamics and dried deposit patterns. The microcavity surface exhibits superior particle capture, thereby revealing its applicability in on‐site testing. Using the direct rapid sampling of analytical materials, the potential of the fabricated microcavity surface for point‐of‐care testing is demonstrated. The proposed microcavity surfaces suggest new avenues for the development of more robust and sensitive sensing platforms.