Contact angles and wetting behaviour of single micron-sized particles

A 'particle interaction apparatus' based on the technique of atomic force microscopy was constructed that allows us to measure the interaction between single micron-sized particles and the air–water interface. From the force versus distance profiles ('force curves') the contact angle of single microspheres could be determined. This new method for microsphere tensiometry was validated using a variety of materials with contact angles between 20° and 90°. Contact angles measured on single microspheres correlated well with those measured on flat substrates of the same materials.