Measurement of Surface Force of Fine Particles at a Short Distance in a Magnetic Fluid under an Electric and Magnetic Field.

Measurement of surface force was performed using an improved surface force apparatus. This apparatus differs from the original SFA employed to measure the surfaces distance. The surface distance measurement method used this time uses dynamic, rather than optical, measurement. This allows improved surface force measurement apparatus based on solution of the low transmission coefficient. Surface force can be measured under both magnetic and electric fields.Based on the results of both surface force measurements, the diameter of magnetite particles coated by active agent was derived from the surfaces distance during the action of the repulsive force.