A Technique for Measuring the Force between a Colloidal Particle in Water and a Bubble

With atomic force microscopes the force between individual colloidal particles and surfaces can be measured. Often, however, the measurement of attractive forces is hampered by the fact that the particle mounted on a force sensor "snaps" or "jumps" onto the surface and no equilibrium force-versus-distance curves can be obtained. Here I describe a technique to overcome this problem. The time course of the snapping-in process was recorded. Based on Newton's equation of motion, kinetic force-versus-distance curves were determined from the time course of the process. With this method 1 measured the force acting on an individual colloidal particle in water (or in air) when it enters an air bubble (or drop).