# Like charged particles at liquid interfaces

UNDER CONSTRUCTION -- Original Entry by Holly McIlwee, AP225 Fall 09

## Overview

Like charged particles at liquid interfaces, M. G. Nikolaides, A. R. Bausch, M. F. Hsu, A. D. Dinsmore, M. P. Brenner, C. Gay, D. A. Weitz. Brief Communications, Nature, 424, August, (2003).

## Soft Matter

Joanna Aizenberg et al. wrote a communication in response to an article Nikolaids et al. wrote in Nature in 2002. In the original paper, it was proposed that the attraction between micron-sized particls and an aqueous interface they are absorbed on is caused by a distortion of the liquid interface due to the dipolar electric field of the particles inducing capillary action.

Aizenberg et al. were compelled to challenge this claim on the basis that they believed that this explanation for the observed attraction does not adhere to force balance laws. Nikolaides et al. assume that the sum of electrostatic pressure acting on the liquid interface is equal to an external force, F, acting on the particle resulting in:

U(r) = F^2/2*Pi*gamma)ln(r/rsubo)

Where: gamma = surface tension r is particle distance rsub0 is a constant

This equation implies that the force acts on the particle and water at the same time. As Aizenberg et al explains, this cannot be the case because the force is balanced by surface tension creating a dimple in the water (as seen in Figure 1) which is governed by the Young-LaPlace equation:

[(1/R1) + (1/R2)]gamma = deltap

McIlwee_Like_Charged_Particles.jpg

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