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Issue 33, 2009
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Photothermal self-stability and optical bistability of single NaCl–water microdroplets on a superhydrophobic surface

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Abstract

A self-stabilization mechanism locking the size of single inorganic salt (NaCl)–water microdroplets that are standing on a superhydrophobic surface and kept in a humidity-controlled chamber is demonstrated. The effect is based on the hysteretic behavior of a photothermal tuning cycle caused by the whispering gallery mode (WGM) absorption resonances that are observed when scanning the power of an infrared laser focused at the rim of a microdroplet. When locked, the microdroplet size and WGM spectrum are resilient to environmental perturbations and can be maintained for hours as the mechanism does not rely on a photobleachable dye. The bistable nature of the system is also demonstrated, enabling reversible switching between two sizes. A rate equation-based thermodynamical model of the hysteretic behavior is provided, giving good agreement with the experimental results. Our results may be used to establish stable experimental conditions for ultrahigh resolution spectroscopy of microdroplets. Other optical and biological applications that require exactly size-matched microdroplets can also benefit from the demonstrated self-stabilization mechanism.

Graphical abstract: Photothermal self-stability and optical bistability of single NaCl–water microdroplets on a superhydrophobic surface

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Publication details

The article was received on 23 Feb 2009, accepted on 14 May 2009 and first published on 10 Jun 2009


Article type: Paper
DOI: 10.1039/B903800K
Citation: Phys. Chem. Chem. Phys., 2009,11, 7145-7151
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    Photothermal self-stability and optical bistability of single NaCl–water microdroplets on a superhydrophobic surface

    Y. Karadag, M. Mestre and A. Kiraz, Phys. Chem. Chem. Phys., 2009, 11, 7145
    DOI: 10.1039/B903800K

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