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Research Paper

Ion Diffusion and DNA Stretching in an Open Nanofluidic System

[+] Author and Article Information
Woon-Hong Yeo

Department of Mechanical Engineering, University of Washington, P.O. Box 352600, Seattle, WA 98195woonhong@uw.edu

Kyong-Hoon Lee

Department of Mechanical Engineering, University of Washington, P.O. Box 352600, Seattle, WA 98195hoonlee@uw.edu

Qingjiang Guo

Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, PA 18015qig210@lehigh.edu

Yaling Liu

Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, PA 18015yal310@lehigh.edu

Xia You

Department of Genome Sciences, University of Washington, P.O. Box 355065, Seattle, WA 98195youxia@uw.edu

John A. Stamatoyannopoulos

Department of Genome Sciences, University of Washington, P.O. Box 355065, Seattle, WA 98195jstam@uw.edu

Jae-Hyun Chung

Department of Mechanical Engineering, University of Washington, Box 352600, Seattle, WA 98195jae71@uw.edu

J. Nanotechnol. Eng. Med 2(1), 011004 (Jan 04, 2011) (6 pages) doi:10.1115/1.4003029 History: Received October 11, 2010; Revised November 10, 2010; Published January 04, 2011; Online January 04, 2011

The ion diffusion in an open nanofluidic system is studied by using an array of nanochannels. The mechanism of the ion diffusion was described through electrowetting-based nanofluidics. An ion diffusion experiment was conducted to validate the theoretical study of the relationship between the diffusion length and the ionic concentration using sodium chloride and phosphate buffer solutions. Shadow edge lithography was utilized to fabricate an array of open nanochannels, which allowed for a direct observation of the molecular diffusion through optical microscopy. The open channel configuration was then applied to stretching λ-DNA molecules in the nanochannels. The stretched length was measured by fluorescence microscopy. The presented nanofluidic device can be applied to the single-molecule study, which can benefit nanoengineered medicine and biology.

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Figures

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Figure 1

Distribution of zeta potential across the channel at various Debye lengths (10)

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Figure 2

(a) Normalized electric field strength near the wall according to ion concentration and (b) normalized diffusion length according to ion concentration (10)

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Figure 3

Nanochannel fabrication: (a) fabrication steps for nanochannels in a Si wafer and (b) SEM images of the fabricated nanochannels. The top image shows the top view of the nanochannels and the inset shows the magnified view of a nanochannel (100×150 nm2). The bottom image shows the cross-sectional view of the nanochannel.

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Figure 4

Schematic of the experimental setup for the nanofluidic experiment

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Figure 5

(a) Diffusion of NaCl solutions at different concentrations in nanochannels: The left image shows ion diffusion with 50 mM NaCl, and the right one shows ion diffusion for 5 mM NaCl. (b) Diffusion images for PB solutions: In the images, the dark area shows channels filled with the ionic solution, while the bright stripes show empty nanochannels.

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Figure 6

Diffusion length variation according to ionic concentrations: (a) NaCl solution and (b) PB solution. Error bars represent standard deviation (n=3).

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Figure 7

Fluorescence images of stretched λ-DNA in nanochannels: (a) nanochannel dimension: 100 nm in width and 150 nm in depth and (b) nanochannel dimension: 50 nm in width and 150 nm in depth

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