Abstract
The ability to precisely control the transport of single DNA molecules through a nanoscale channel is critical to DNA sequencing and mapping technologies that are currently under development. Here we show how the electrokinetically driven introduction of DNA molecules into a nanochannel is facilitated by incorporating a three-dimensional nanofunnel at the nanochannel entrance. Individual DNA molecules are imaged as they attempt to overcome the entropic barrier to nanochannel entry through nanofunnels with various shapes. Theoretical modeling of this behavior reveals the pushing and pulling forces that result in up to a 30-fold reduction in the threshold electric field needed to initiate nanochannel entry. In some cases, DNA molecules are stably trapped and axially positioned within a nanofunnel at sub-threshold electric field strengths, suggesting the utility of nanofunnels as force spectroscopy tools. These applications illustrate the benefit of finely tuning nanoscale conduit geometries, which can be designed using the theoretical model developed here.
Highlights
The ability to precisely control the transport of single DNA molecules through a nanoscale channel is critical to DNA sequencing and mapping technologies that are currently under development
We describe the fabrication of nanochannels having three-dimensional nanofunnel entrances of various shapes using focused ion beam (FIB)-milling, visualization of DNA behavior in these nanofunnels, and modeling of this behavior to better understand how controlling the geometry of the nanochannel entrance can enhance the electrokinetic manipulation of DNA molecules in nanofluidic platforms
The frequency of DNA threading can be increased by applying a larger voltage, this approach is problematic if the resulting DNA transport velocity exceeds the sampling rates of electronic or optical detection modes[13,14,15,16,17,18,19]
Summary
The ability to precisely control the transport of single DNA molecules through a nanoscale channel is critical to DNA sequencing and mapping technologies that are currently under development. Experimental measurements confirmed, that the forces experienced by the DNA molecule in the nanofunnel result in compression of the DNA leading sections towards the nanochannel entrance by DNA trailing sections, an effect that we refer to as an electro-osmotic piston.
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