Abstract

I will discuss my work in microfludics for DNA analysis and for sorting of particles. DNA forced into confinement in channels with diameter approaching the persistence length of the DNA will adapt an elongated conformation. The end-to-end distance is proportional to the contour length of the DNA for the two prevailing models: for channels with diameters << persistence length the stiffness of the DNA prevents it from folding back on itself (Odijk regime) and forB channels with diameters >> persistence length excluded volume effects dominate (deGennes regime). One interesting recent experimental result is the strong dependence of the extension of the DNA on the ionic strength. We show that a modified deGennes model based on the salt-dependence of the effective width can be used to accurately describe the behavior of the DNA at ionic strengths ranging from 2mM to 200mM in channels with diameters 100nm or larger. The benefits of stretching DNA in small channels will be discussed together with future plans such as a soon to start project on a combined magnetic tweezers and nanofluidic channels. Another field of interest in our group is microfluidic devices for fractionation of particles. I will discuss recent results on deterministic lateral displacement which is a powerful technique to separate particles in the micrometer range with uncertainties around 1%. The device works like a cut-off filter, sending larger particles in one direction and smaller particles in another. To make the device adjustable we have made the device in an elastic material so that simply by stretching the entire device we can adjust the cut-off size.B