Withdrawal of a conical pin from a pool of liquid

A. B. Wang, Y. S. Chen, Y. J. Wu, J. Y. Sung, A. L. Yarin

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


The development of biochips leads to a straightforward, fast and cost effective method to obtain valuable genetic information. A key element of the emerging biochip technology is a microarray system, which fabricates high-density samples on solid materials of a microscopic area. In particular, dots of test liquid are printed on solids by a system of pins constituting a microarray. At present, however, the technique cannot make dots of arbitrary equivalent and controllable size. On the other hand, printing pins in microarrays represent themselves as a particular example of dip coating. In the experiments of the present work, a model of tapered stainless steel needle was withdrawn from different glycerine-water mixtures. Thicknesses and volumes of the withdrawn liquid films were measured as a function of the needle geometry, immersion depth, withdrawal rate, and physical parameters of the liquid. The experimental data are analyzed as a function of the capillary number Ca based on the withdrawal speed and compared to the predictions of the modified Landau-Levich-Deryagin (LLD) theory. The results show that for Ca < 10 -2 the thickness and the volume of the liquid follow the Ca 2/3-scaling, while for Ca > 10-2 - the Ca 1/2-scaling, as it is expected from the LLD theory. Flow visualization is utilized to resolve the detail flow structure. The results put the key element of the pin-printing technology exploited in microarrays into a familiar hydrodynamic context of dip coating. This allows one to expect that under appropriate operational conditions, high-precision sampling could be attainable.

Original languageEnglish
Pages (from-to)219-232
Number of pages14
JournalJournal of Mechanics
Issue number3
Publication statusPublished - 2004 Sept


  • Conical pin
  • Flow visualization
  • Withdrawn liquid

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanical Engineering
  • Applied Mathematics


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