Deformation of DNA molecules by hydrodynamic focusing

Pak Kin Wong, Yi Kuen Lee, Chih Ming Ho

Research output: Contribution to journalArticlepeer-review

100 Scopus citations


The motion of a DNA molecule in a solvent flow reflects the deformation of a nano/microscale flexible mass-spring structure by the forces exerted by the fluid molecules. The dynamics of individual molecules can reveal both fundamental properties of the DNA and basic understanding of the complex rheological properties of long-chain molecules. In this study, we report the dynamics of isolated DNA molecules under homogeneous extensional flow. Hydrodynamic focusing generates homogeneous extensional flow with uniform velocity in the transverse direction. The deformation of individual DNA molecules in the flow was visualized with video fluorescence microscopy. A coil-stretch transition was observed when the Deborah number (De) is larger than 0.8. With a sudden stopping of the flow, the DNA molecule relaxes and recoils. The longest relaxation time of T2 DNA was determined to be 0.63s when scaling viscosity to 0.9 cP.

Original languageEnglish (US)
Pages (from-to)55-65
Number of pages11
JournalJournal of Fluid Mechanics
StatePublished - Dec 25 2003

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering


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