Abstract
Here, the enhancement of the overall mass transfer and separation of double stranded DNA (dsDNA) in a microchannel using steady and pulsatile flow is studied... The degree of separation was seen to increase with oscillatory flow as compared to steady conditions. It was also observed that the separation improved with increasing oscillation amplitude until reaching a certain critical point when the oscillations were large enough to begin promoting mixing. The study achieves the initial goal of proof-of-concept of microscale separation through electroosmotic flows and furthers the effort of building a handheld `lab-on-a-chip' device that could be used to rapidly analyze a variety of biomolecules.
Microchannel castings were made using polydimethyl siloxane (PDMS). A mixture of 10mer and 50mer dsDNA along with another mixture of 10mer and 100mer dsDNA were used to visualize the separations using epifluorescence microscopy. The observations were characterized using a spectrophotometer which utilized a program known as Avasoft 8. The peak-to-peak separation distance between the dsDNA species demonstrated a dependence on the microchannel geometry, the electrical double layer, and the amplitude of the oscillations. Numerical velocity profiles and concentration tracking plots were generated with COMSOL Multiphysics to provide further insight and understanding of the dependency of these characteristics on the separation process.