Microscale Computed Tomography (μCT) Imaging of Leak Pathways for Optimized Leak-Free 3D Printed Fluidics.

3D printing is a highly attractive method for manufacturing micro- and millifluidic devices due to fast fabrication times and a low barrier to entry. Of the common 3D printing methods, fused filament fabrication (FFF) is the most accessible but is also susceptible to leakages when using default printer settings. Here, we combine microscale computed tomography (μCT) X-ray imaging with bulk leak testing to understand the fundamental structural reasons why leakages occur, and the effect of optimizing print parameters. In contrast to previous recommendations, we show that the amount of infill can be reduced as required, with print bodies being intrinsically porous, regardless of infill. Instead, we find that it is solely the channel wall quality that determines whether leaks will occur. In keeping with previous reports, we see that smaller layer heights (<0.1 mm) and increased flow rates (>100% compared to the recommended rate) are key to preventing leakage, and show this is because of their positive effect on channel wall formation. A key consequence of being able to maintain channel integrity while using low infill values is that print times and material costs can be greatly reduced (over 50% time and cost savings for the test pieces used here) without compromising device performance.