Influence of the axial displacement of a trapped bead on the calibration of the force parameters of optical tweezers

Jian Hua Bao*, Zan Gong, Hong Tao Chen, Zhong Wang, Yin Mei Li, Li Ren Lou

*Corresponding author for this work

Research output: Contribution to journalArticle

3 Scopus citations

Abstract

As a force probe, optical tweezers have two important parameters: trap stiffness and escape force. The drag-force method is often used to calibrate these parameters in the lateral direction. In that case the axial displacement of the trapped bead is usually neglected and its influence on the calibration precision has not been studied. In this work the information entropy method is used to measure the axial displacement in the calibration. Then its influence on the calibration is analyzed. The result shows that the trapped bead displaces axially as well as laterally when the surrounding medium flows. So the trap stiffness measured in this way is not really on the same horizontal plane, which is one of the error sources of the calibration. The experimental date also shows that there is a jump in the axial displacement of the bead when the fluid velocity reaches the critical value. This fact indicates that the bead escapes from the trap upward in stead of laterally and hence the measured escape force is not the maximal radial or lateral trapping force as commonly accepted.

Original languageEnglish (US)
Pages (from-to)1421-1424
Number of pages4
JournalZhongguo Jiguang/Chinese Journal of Lasers
Volume32
Issue number10
StatePublished - Oct 1 2005
Externally publishedYes

Keywords

  • Axial displacement
  • Drag-force method
  • Escape force
  • Information entropy
  • Optical trap
  • Quantum optics
  • Trap stiffness

ASJC Scopus subject areas

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

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