Self-assmbled Lithography-free Fabrication Of Microchannels And Microfluidics In Polymers
Kahsai, Wintana Tadesse
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Rapid, reliable and easy to implement approaches are needed for fabrication of circular microchannels in polymeric microfluidics. PDMS has been a choice of material in microfluidics and it is being used as prototype due to its unique property such as flexibility and transparency. Traditional method of fabrication such as photolithography and soft lithography are complicated and time consuming. In this thesis, a non-lithography and bottom-up self-assembled approach is shown. The resulting devices can have uses in many applications such as assays, biosensing, separation of mixtures, micro-mixing and bioreactors. This thesis presents novel approaches of manufacturing self-assembled microchannels in polydimethyleneoxide (PDMS) membranes. The underlying principle is based on the hydrophobic-hydrophilic interactions of different molecules with PDMS. Iron-oxide nanoparticles, acetone, and polymers such as poly urethane (PU) and poly ethylene oxide (PEO) are hydrophilic materials used to induce channel formation in the membranes of PDMS which is hydrophobic. The process is systematic, flexible in design, easy to implement, rapid, inexpensive and does not require lithography.The technique yielded a controlled way to fabricate microchannels with a range of pore sizes, porosity and lengths. This was done by tweaking various parameters such as temperature, curing agent concentration, magnetic field, and different types of hydrophilic particles. Results showed channel diameters ranged from few micrometers. Fluid flow in fabricated microchannels under capillary action was also demonstrated and mixing of fluids in plasma treated and bare PDMS was analyzed.