Microparticle manipulation using inertial forces

We demonstrate controlled manipulation of large quantities of microparticles on a surface using inertial forces. Motion is induced by applying a periodic parabolic wave form to a shear-polarized piezoelectric plate coupled to a substrate on which the particles reside. Particles move in steps of 10 to 50 nm per cycle, and the particle motion is mass selective. Particle velocity is varied by changing the frequency of the wave form. Calculated inertial forces acting on the particles correspond closely to friction forces between individual microparticles and the substrate, as measured by coupling an individual particle to an atomic force microscope. The results provide insight into the characteristics of particle-surface interactions, and demonstrate the potential for controlled manipulation and separation of large collections of particles without the need for a fluid medium. (c) 2006 American Institute of Physics.