Volume 112, Number 4, November 2015
|Number of page(s)||7|
|Section||Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics|
|Published online||24 November 2015|
Probing the Casimir force with optical tweezers
1 Instituto de Física, Universidade Federal do Rio de Janeiro - Rio de Janeiro, RJ, 21941-972, Brazil
2 LPO-COPEA, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro Rio de Janeiro, RJ, 21941-902, Brazil
3 Institut für Physik, Universität Augsburg - Universitätsstraße 1, D-86135 Augsburg, Germany
4 Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro - Rio de Janeiro, RJ, Brazil
Received: 30 October 2015
Accepted: 10 November 2015
We propose to use optical tweezers to probe the Casimir interaction between microspheres inside a liquid medium for geometric aspect ratios far beyond the validity of the widely employed proximity force approximation. This setup has the potential for revealing unprecedented features associated to the non-trivial role of the spherical curvatures. For a proof of concept, we measure femtonewton double-layer forces between polystyrene microspheres at distances above 400 nm by employing very soft optical tweezers, with stiffness of the order of fractions of a fN/nm. As a future application, we propose to tune the Casimir interaction between a metallic and a polystyrene microsphere in saline solution from attraction to repulsion by varying the salt concentration. With those materials, the screened Casimir interaction may have a larger magnitude than the unscreened one. This line of investigation has the potential for bringing together different fields including classical and quantum optics, statistical physics and colloid science, while paving the way for novel quantitative applications of optical tweezers in cell and molecular biology.
PACS: 42.50.Ct – Quantum description of interaction of light and matter; related experiments / 87.80.Cc – Optical trapping / 82.70.Dd – Colloids
© EPLA, 2015
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