Superhydrophobic surfaces for microfluidic applications

Abstract: The integration and use of superhydrophobic surfaces to microfluidic systems were investigated in this work. Superhydrophobic surfaces are believed to have the ability to reduce the hydrodynamic resistance of a microchannel, reduce the risk of clogging due to reduced liquid contact with the microchannel walls and reduce the losses in a microfluidic system. Two superhydrophobic surfaces with different fabrication methods were evaluated. It was found that fabrication methods that add material to the microchannel walls do not work well in microchannels. Methods that instead transform a present surface are more suitable for a microfluidic system. To visualize the superhydrophobic surfaces an AFM and SEM were used. By combining the information a good picture of the superhydrophobic surfaces where sometimes achieved. To investigate the impact of the superhydrophobic surfaces, two different designs of microchannels were created on silicon wafers and compared with microchannels created in polydimethylsiloxane. One design used straight channels and the other aimed to maximize the resistance reduction by patterning the walls of the microchannel. Due to manufacturing issues only the straight channels were evaluated, where it was found that superhydrophobic surfaces can increase the flow rate of a microfluidic system. However, the result was not reproduced easily. The reason is currently unknown but believed to originate from flaws in the manufacturing process. A simple version of a device that uses superhydrophobic surfaces to seal microfluidic systems was successfully used and reused. A device with a more refined design could offer the ability to create microfluidic systems with detachable lids. Finally, to further increase the availability of the properly created superhydrophobic surface an alternative functionalization step should be found.