Issue
EPL
Volume 88, Number 4, November 2009
Article Number 48005
Number of page(s) 6
Section Interdisciplinary Physics and Related Areas of Science and Technology
DOI http://dx.doi.org/10.1209/0295-5075/88/48005
Published online 03 December 2009
EPL, 88 (2009) 48005
DOI: 10.1209/0295-5075/88/48005

Quantification of droplet deformation by electromagnetic trapping

P. C. F. Møller and L. B. Oddershede

Niels Bohr Institute, University of Copenhagen - Blegdamsvej 17, 2100 Copenhagen, Denmark, EU

oddershede@nbi.dk

received 18 September 2009; accepted in final form 6 November 2009; published November 2009
published online 3 December 2009

Abstract
A tightly focused laser beam exerting a trapping force on an object also exerts deformation forces on the object. If the object is relatively easy to deform, as is, e.g., a low surface tension droplet, the resulting deformation is easily detectable even at moderate laser powers. The observed deformation is analytically explained by a model, which quantitatively predicts the deformation of any micron-sized drop where the only restoring force is the surface tension. Theoretical tools are also provided to include the effect of elasticity of the shell and bulk of the trapped object, this being particularly important for deformations of cells. This deformation effect of electromagnetic radiation is important to consider while trapping soft materials and it can be used to determine physical characteristics of soft materials.

PACS
87.80.Cc - Optical trapping.
42.50.Wk - Mechanical effects of light on material media, microstructures and particles.

© EPLA 2009