LATERAL CAPILLARY FORCES AND 2-DIMENSIONAL ARRAYS OF COLLOID PARTICLES AND PROTEIN MOLECULES

This paper presents a review of our recent studies on the lateral capi llary forces and on their role in the formation of two-dimensional ord ered arrays of colloidal particles or protein molecules. To reveal the mechanism of protein ordering in liquid films we carried out model ex periments with micrometer sized latex particles. The films were formed on solid or liquid substrates. By variation of the electrolyte concen tration, the particle charge and volume fraction we proved that neithe r the double layer repulsion, nor the van der Waals attraction between the particles, was responsible for the formation of the two-dimension al arrays. Direct microscope observations revealed that the process of ordering was triggered by attractive lateral capillary forces due to the overlap of the menisci formed around the particles. Two types of l ateral capillary forces, flotation and immersion, could be distinguish ed and theory of these interactions was developed. The lateral capilla ry forces between a floating particle and a wall were also studied; th ey could be employed for precise determination of the shear surface vi scosity.