Attractive forces on hard and soft colloidal objects located close to the surface of an acoustic-thickness shear resonator.
Colloidal particles located close to the surface of an acoustic thickness shear resonator feel an attractive steady force, which is induced by the high-frequency tangential motion of the resonator surface. The range of the force is about half the penetration depth of the transverse viscous wave, that is, half of the thickness of the Stokes boundary layer. For an oscillation amplitude of 10 nm and a particle radius of 100 nm, the depth of attractive potential well corresponds to about 3 times the thermal energy, k(B)T. The force therefore suffices to overcome Brownian motion.
Institute of Physical Chemistry, Clausthal University of Technology, 38678 Clausthal-Zellerfeld, Germany.
Arne
A
Langhoff
Diethelm
D
Johannsmann