A MEMS electrostatic particle transportation system

We demonstrate here an electrostatic MEMS system capable of transporting particles 5-10 mu m in diameter in air. This system consists of three-phase electrode arrays covered by insulators. Extensive testing of this system has been done using a variety of insulation materials (silicon nitride, photoresist and Teflon), thickness (0-12 mu m), particle sizes (1-10 mu m), particle materials (metal, glass, polystyrene, spores, etc.), waveforms, frequencies and voltages. Although previous literatures [D.W. Cooper, H.L. Wolfe, J.T.C. Yeh, R.J. Miller, Surface cleaning by electrostatic removal of particles, Aerosol Science and Technology 13 (1990) 116-123; V.J. Novick, C.R. Hummer, P.F. Dunn, Minimum electric field requirements for removing powder layers from a conductive surface, Journal of Applied Physics 65 (1989) 3242-3247] claimed it is impractical to electrostatically transport particles with sizes 5-10 mu m due to complex surface forces, this effort actually shows it is feasible (as high as 90% efficiency) using the optimal combination of insulation thickness, electrode geometry and insulation material. Moreover, we suggest a qualitative theory for our particle transportation system which is consistent with our data and finite-element electrostatic simulations. (C) 1999 Elsevier Science S.A. All rights reserved.