A comparison between the hydrodynamic characteristics of 3D-printed polymer and etched silicon microchannels

The use of 3D-printing as a microfabrication approach has potential to address contemporary challenges in microfluidic applications including rapid prototyping, complex channel layouts and sealing. The hydrodynamic characteristics of 3D-printed embedded microchannel arrays have been experimentally examined in this paper. Conventional silicon fabrication processes using deep reactive ion etching techniques (DRIE) and wet-etching (KOH) are used as a benchmark for comparison. Rectangular, trapezoidal and circular cross-sectional shapes were considered. The channel arrays were 3D-printed in vertical and horizontal orientations, to examine the influence of print orientation on channel characteristics. These characteristics included cross-sectional area (CSA), surface features and pressure-flow behavior. The etched silicon channels were found to be dimensionally superior, with channel-to-channel variances in CSA of 2.7 and 5.0 % for DRIE and KOH, respectively. The 3D-printed microchannel arrays demonstrated larger variance in CSA (6.6-20 %) with the vertical printing approach yielding greater dimensional conformity than the horizontal. The 3D-printed microchannel arrays had a consistently smaller value of CSA than the nominal, with a noticeable feature of the horizontal approach being additional sidewall roughness leading to shape distortion. The hydrodynamic measurements revealed the etched silicon microchannel arrays to be in agreement with laminar flow theory (within +/- 10 % for DRIE and KOH, respectively) using the nominal geometric data. 3D-printing in a vertical orientation produced lower fidelity channels with differences of up to 24.5 % between the actual printed geometry and the nominal input. Horizontally printed microchannels were found to have significantly larger differences of up to 103.8 %. Using the measured geometric data, theory provided a reasonable prediction of the hydrodynamic performance of the printed channels. It was concluded that vertical 3D-printing is superior to the horizontal 3D-printing approach for creating microchannel arrays to transport fluids. This finding is useful to practitioners using 3D-printing for microfabrication and rapid turnaround microfluidic applications.