A method using total internal reflection microscopy and radiation pressure to study weak interaction forces of particles near surfaces

Abstract

An apparatus has been built which allows, by radiation pressure forces, the manipulation of a single colloid particle, immersed in water, close to a flat surface. The particle movement is monitored by total internal reflection microscopy (TIRM). Preliminary results are presented which illustrate the usefulness of the technique for studying the weak interactions between a 10-µ polystyrene latex particle and a quartz glass surface. An interaction potential energy curve as a function of the relative separation between the particle and the surface has been obtained.

Direct Measurement of the Effect of Surface Roughness on the Colloidal Forces between a Particle and Flat Plate

“…This tech- nique was first demonstrated by Brown et al (15) and was upward force on the particle, which acts to effectively lower the net particle weight, can be measured and subtracted from later adopted in a similar design by Walz and Prieve (16). It was shown that a laser beam directed upward against the measured potential energy profiles so that it does not affect the final results.…”

Measurement of surface charge densities on Brownian particles using total internal reflection microscopy

“…2. The idea of using light forces to control the movement of the particle has been introduced to the TIRM method by Brown et al 28 and Walz et al 29 In our case both tweezers were formed by a 200 mW frequency doubled Nd:YAG laser (ϭ532 nm). As the upper tweezer we employed a strongly focused laser beam with an adjustable intensity of 50-150 mW.…”

A new approach for analyzing particle motion near an interface using total internal reflection microscopy

“…Adamczyk et al [3] experimentally confirmed Brenner's correction factor to the bulk particle mobility by measuring the sedimentation rate of nylon spheres through a viscous oil toward different shaped surfaces. Brown and Staples [4][5][6] studied the dynamics of Brownian particles above a quartz plate at small separation distance using the combined optical techniques of radiation pressure and total internal reflection microscopy (TIRM). The authors calculated the absolute separation distance of the particle from the surface assuming Brenner's lubrication theory to be valid.…”