EXPERIMENTAL STUDY OF THE TRANSFER OF MICROPARTICLES IN A THIN LIQUID LAYER UNDER THE INFLUENCE OF A TEMPERATURE GRADIENT

Abstract

This article studies the main regularities of polyethylene microparticles transfer process in a layer of volatile and non-volatile fluid by thermocapillary currents under local heating and cooling. The authors show the possibility of creating circular and ring-shaped patterns by inducing positive and negative radial-directional temperature gradients. A methodology and computer program have been developed to quantify the transfer process, consisting in measuring the area of the particle pattern (assembly) formed during heating and the area freed from the particles (cleaning area) during cooling on a sequence of video recording frames obtained with an optical microscope. This technique is based on comparing the intensity of image pixels with respect to a threshold value and counting the total area of pixels occupied or not occupied by particles. The influence of such experiment parameters as the volume of the carrier fluid (layer thickness), at a constant number of particles, fluid evaporation and the ratio of particle and fluid densities on the size of the resulting pattern and the time of reaching the steady state has been established. The results show that the area of the final pattern during local heating and the clearing area, during local cooling, tends to decrease with increasing layer thickness, while the time of reaching the steady state does not depend on the layer thickness, but depends on the properties of the liquid and the ratio of particle and liquid densities.