A Comparison between the Hydrodynamic Characteristics of 3D-Printed Polymer and Etched Silicon Microchannels

The use of 3D-printing as a micro-fabrication 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 dimension- ally 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 side-wall 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 micro-fabrication and rapid turnaround microfluidic applications.