ETH Polymer Physics seminar


2011-11-16
11:00 at HCI J 574

DNA Polymer Dynamics in Nanoconfinement and Electric Fields

Patrick Doyle

Chemical Engineering, MIT, USA

The development of fluorescence microscopy of single-molecule DNA in the last decade has fostered a bold jump in the understanding of polymer physics. With the recent advance of nanotechnology, devices with well-defined dimensions that are smaller than typical DNA molecules can be readily manufactured. The combination of these techniques has provided an unprecedented opportunity for researchers to examine confined polymer behavior, a topic far less understood than its unconfined counterpart. We have used a nanofluidic cross-slot device to investigate the influence of slit-like confinement on the coil-stretch transition of single DNA molecules in a 2D homogeneous extensional electric field. In contrast to microchannels, DNA molecules in the nanochannels exhibit highly modified coil-stretch processes. Specifically, the onset of DNA stretching starts earlier, the transition progresses more gradually, and most importantly, we identify two distinct critical strain rates in the transition. We have constructed a Brownian dumbbell model that is able to provide qualitative predictions of the coil-stretch transition of DNA in confinement. We will also discuss some recent experiments in which we see an unexpected compression of DNA in DC electric fields, and what we believe are self-entangled polymer states.


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