Microscale imaging of leak pathways in FDM 3D printed fluidics

Abstract

3D printing is a highly attractive method for manufacturing micro- and milli-fluidic devices due to fast fabrication times and low barrier to entry. Of the common 3D printing methods, fused deposition modelling (FDM) is the most accessible but is also susceptible to leakages if printed with default settings. Previous reports have described how specific print parameters are required to ensure reliable leak-free fluidics including increased flow rates, small layer heights, and 100% infill. Here we combine computer tomography (CT) X-ray imaging with bulk leak testing to understand the fundamental structural reasons for the previously reported recommended print parameters. In keeping with previous reports, we see that smaller layer heights (<0.1 mm) and increased flow rates (>100 % compared to recommended rate) prevent leakage. We show these two parameters prevent leaks by increasing the quality and integrity of channel walls, though the relevant importance of each parameter depends on whether channels are orientated vertically or horizontally compared to the print bed. In contrast to previous reports, we show that the degree of infill is irrelevant as print bodies are intrinsically porous and it is the integrity of channel walls that determines whether leaking will occur. Consequently channels can be printed with low infills without sacrificing leak integrity and consequently print times and material costs can be greatly reduced (over 50 % time and cost savings for the test pieces used here).