Critical Casimir interactions between Janus particles

• Published in: Soft matter Vol. 12; no. 31; pp. 6621 - 6648
• Main Authors: Labbé-Laurent, M, Dietrich, S
• Format: Journal Article
• Language: English
• Published: England 01.01.2016
• Subjects: Approximation; Assembly; Mathematical analysis; Nanoparticles; Quantum theory; Self assembly; Stands; Substrates
• ISSN: 1744-683X; 1744-6848
• DOI: 10.1039/c6sm00990e

Recently there has been strong experimental and theoretical interest in studying the self-assembly and the phase behavior of patchy and Janus particles, which form colloidal suspensions. Although in this quest a variety of effective interactions have been proposed and used in order to achieve a directed assembly, the critical Casimir effect stands out as being particularly suitable in this respect because it provides both attractive and repulsive interactions as well as the potential of a sensitive temperature control of their strength. Specifically, we have calculated the critical Casimir force between a single Janus particle and a laterally homogeneous substrate as well as a substrate with a chemical step. We have used the Derjaguin approximation and compared it with results from full mean field theory. A modification of the Derjaguin approximation turns out to be generally reliable. Based on this approach we have derived the effective force and the effective potential between two Janus cylinders as well as between two Janus spheres. Based on the Derjaguin approximation, we have derived the critical Casimir force and the effective potential between a Janus particle and a chemical substrate, between two Janus cylinders as well as between two Janus spheres immersed in a suspension close to a critical point.