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Issue 13, 2014
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Alignment of cylindrical colloids near chemically patterned substrates induced by critical Casimir torques

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Abstract

Recent experiments have demonstrated a fluctuation-induced lateral trapping of spherical colloidal particles immersed in a binary liquid mixture near its critical demixing point and exposed to chemically patterned substrates. Inspired by these experiments, we study this kind of effective interaction, known as the critical Casimir effect, for elongated colloids of cylindrical shape. This adds orientational degrees of freedom. When the colloidal particles are close to a chemically structured substrate, a critical Casimir torque acting on the colloids emerges. We calculate this torque on the basis of the Derjaguin approximation. The range of validity of the latter is assessed via mean-field theory. This assessment shows that the Derjaguin approximation is reliable in experimentally relevant regimes, so that we extend it to Janus particles endowed with opposing adsorption preferences. Our analysis indicates that critical Casimir interactions are capable of achieving well-defined, reversible alignments both of chemically homogeneous and of Janus cylinders.

Graphical abstract: Alignment of cylindrical colloids near chemically patterned substrates induced by critical Casimir torques

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Publication details

The article was received on 12 Nov 2013, accepted on 05 Dec 2013 and first published on 10 Feb 2014


Article type: Paper
DOI: 10.1039/C3SM52858H
Citation: Soft Matter, 2014,10, 2270-2291
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    Alignment of cylindrical colloids near chemically patterned substrates induced by critical Casimir torques

    M. Labbé-Laurent, M. Tröndle, L. Harnau and S. Dietrich, Soft Matter, 2014, 10, 2270
    DOI: 10.1039/C3SM52858H

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