1999-03-02
10:15 at CAB D28

Surface Forces and Deformation of a Fluid Drop approaching a Solid Plate

Roger Horn

Ian Wark Research Institute, Mawson Lakes, SA 5095, Adelaide, Australia

This talk describes some new experiments conducted in a version of the Surface Force Apparatus, which has been modified to allow measurements between one flat solid surface (mica) and a fluid drop (mercury) when both are immersed in water. The main object of these experiments is to investigate the interplay between surface forces, hydrodynamic forces and deformation of the fluid drop. It will be shown that drop deformation has a major influence on the forces between the drop and the solid, and some implications for colloidal systems of dispersed drops will be discussed. A particular feature of our experiments is that since we are using mercury as a fluid, it is possible to apply an electrical potential to the mercury and thereby control its electrical double-layer interactions with mica. Results will be presented showing the variation of mica-mercury separation as a function of applied potential, and our initial attempts at analysing the data in such a way as to extract information about the structure of the double layer will be described.