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Rev Sci Instrum. 2008 Feb;79(2 Pt 1):023710. doi: 10.1063/1.2884147.

Optical tweezers with 2.5 kHz bandwidth video detection for single-colloid electrophoresis.

Author information

1
Institute of Experimental Physics I, Leipzig University, Linnéstr. 5, 04103 Leipzig, Germany.

Erratum in

  • Rev Sci Instrum. 2012 Dec;83(12):129901.

Abstract

We developed an optical tweezers setup to study the electrophoretic motion of colloids in an external electric field. The setup is based on standard components for illumination and video detection. Our video based optical tracking of the colloid motion has a time resolution of 0.2 ms, resulting in a bandwidth of 2.5 kHz. This enables calibration of the optical tweezers by Brownian motion without applying a quadrant photodetector. We demonstrate that our system has a spatial resolution of 0.5 nm and a force sensitivity of 20 fN using a Fourier algorithm to detect periodic oscillations of the trapped colloid caused by an external ac field. The electrophoretic mobility and zeta potential of a single colloid can be extracted in aqueous solution avoiding screening effects common for usual bulk measurements.

PMID:
18315308
DOI:
10.1063/1.2884147
[Indexed for MEDLINE]

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