Experimental Investigations of Capillary Flow in Three-Dimensional-Printed Microchannels

In recent years, the application of microfluidic devices has increased, and three-dimensional (3D) printers for fabricating microdevices could be considered a suitable technique but, in some cases, may confront some issues. The main issues include channel roughness values, print orientation due to the 3D printer’s setup, filament materials, nozzle specifications, and condition. This study aims to analyze the capillary-driven flow in microdevices produced by 3D printers. Therefore, four 3D printer-based microchannels were investigated, and the capillary-driven flow of five liquids with different viscosities and contact angles was evaluated experimentally. The experimental results were compared with theoretical calculations using the Lucas−Washburn equation, and the impact of the width, length, and closed and open microchannel on flow behaviors was explored. The experimental results showed that the peak velocity for open and closed microchannels decreases with the length. Moreover, there were differences in flow behavior between open and closed microchannels. For the former, the maximum average velocity appeared in the microchannel with a width of 400 μm, while for the latter, it was for a width of 1000 μm. In addition, the flow velocity decreased when the viscosity increased, regardless of microchannel width. The decrease was more pronounced for the lower-viscosity liquids (ethanol and water) and smaller for the higher-viscosity ones (coffee and olive oil). Finally, the advantages and challenges of 3D printer-based microdevices are presented.