PERTURBATION ANALYSIS OF DROPLET DEFORMATION UNDER ELECTRICAL DOUBLE-LAYER FORCES

Fluid-liquid interface deformation by electrical double layer surface forces introduces several difficulties for the accurate interpretation of fluid-drop-particle interaction measurements. We investigate the s ource of these difficulties theoretically using a perturbation method. Relevant quantities, such as interface shape and droplet internal pre ssure, are expressed in series expansions in a dimensionless parameter M=(n(0)k(B)T)/(gamma ll), being the ratio of electrical double layer forces to surface tension, i.e., an effective double layer Bond number . Governing equations are truncated to first order in M, and solved fo r the deformation in droplet shape to leading order. Analytical and nu merical results for the case of neutrally buoyant drops interacting wi th charged spherical particles allow for a quantitative examination of the extent of deformation. The case of drops experiencing finite buoy ancy is also formulated ina linear theory, and a method of solution is outlined.