Measurement of the capillary interaction force between Janus colloidal particles trapped at a flat air/water interface.
basic_science · Level V
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- Record sourced from PubMed, PMID 32567631.
- Also identified by DOI 10.1039/d0sm00288g.
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Abstract
The capillary interaction force between spherical Janus particles trapped at the air-water interface is measured using a time-sharing optical tweezer (bond number ≪ 1). One face of the particles is hydrophilic, and the other one, hydrophobic. Measured force goes from almost pure quadrupolar to almost pure hexapolar interaction due to the three-phase contact line corrugation. Measured force curves are modeled as a sum of power laws, Ar<sup>-α</sup> + Br<sup>-β</sup> + Cr<sup>-γ</sup>, obtained from an expansion in capillary multipoles. The mean values for the exponents of particle pairs of 3 μm are 〈α〉 = 5.05 ± 0.12, 〈β〉 = 7.02 ± 0.03, and 〈γ〉 = 5.96 ± 0.03. For particles pairs of 5 μm, we find 〈α〉 = 5.02 ± 0.04, 〈β〉 = 6.94 ± 0.06, and 〈γ〉 = 5.80 ± 0.05. In both cases, A < 0, B < 0, and C > 0.