Single-stranded DNA concentration by electrokinetic forces

Han Cheng, Kin Fong Lei, Kit Ying Choy, Ming Cheung Chow

Research output: Journal article publicationJournal articleAcademic researchpeer-review


Electrokinetics provide an effective molecular manipulation technique in micro/nano fluidic environments, which match the length scale of various biological objects. In this work, two circular gold electrodes are fabricated on a glass substrate as DNA concentrators. A combination of alternating current (ac) electro-osmosis and electrophoresis is used to concentrate single-stranded DNA (ssDNA) molecules as small as 20 nucleotides in length. To understand the phenomenon of ac electro-osmotic flow, numerical simulation of the flow field is done and shows that the effective fluid flow is up to 100 μm above the electrode surface. Hence, ssDNA molecules labeled with fluorescent dye are utilized to demonstrate the concentration effect on the DNA concentrator. ac electro-osmotic flow induced by the ac electric field can stir the bulk fluid, and ssDNA molecules can be transported from a large effective region to the surface of DNA concentrator. In addition, electrophoretic force induced by direct current (dc) bias is applied simultaneously to attract and hold ssDNA molecules. The motion of ssDNA molecules under electrokinetic forces is observed under a fluorescence microscope. The experimental results show that the ssDNA molecules can be concentrated on the electrode surface instantly. ssDNA concentration under different conditions is also compared and the results generated are discussed.
Original languageEnglish
Article number021107
JournalJournal of Micro/Nanolithography, MEMS, and MOEMS
Issue number2
Publication statusPublished - 1 Jan 2009


  • Alternating current electro-osmosis
  • DNA concentration
  • Electrokinetics
  • Electrophoresis

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Mechanical Engineering
  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Atomic and Molecular Physics, and Optics


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