Electrostatic particle transportation

Details Electrostatic particle transportation Electrostatic particle transportation

1998-10-06

2001-02-06

Jackson, Stephen W. (Department: 2836)

Electricity: electrical systems and devices

Electric charge generating or conducting means

C361S225000, C361S226000

Reexamination Certificate

active

06185084

ABSTRACT:

TECHNICAL FIELD
The present disclosure relates to the electrostatic transportation of particles.
BACKGROUND
Transport of particles is fundamental to many instruments including airborne samplers, particle sorters, and electrostatic cleaning apparatuses. Specifically, the particle diameter range from 1 to 10 &mgr;m is of significant importance because many airborne pollutants such as biological spores, dust particles, and chemical agents fall into this geometric size range. In addition, other airborne pollutants, orders of magnitude smaller than this size range, have also been dispersed in air with the aid of larger carrier particles which are in the 1-10&mgr;m size scale. Therefore, such a particle transport device becomes a vital component of a wide range of instruments.
Electrostatic particle transportation for 1-10 &mgr;m sized particle has been an unresolved task for engineers. Devices for manipulation and transport have been developed for larger size ranges of particles, but not in the 1 to 10 &mgr;m particle scales. Surface forces and particle charging become difficult issues in successfully engineering a robust particle transport mechanism. For example, Novick, Hummer, and Dunn have noted that the sub-10 &mgr;m range presents a different regime where surface adhesive forces and particle charging hinder the successful engineering of a robust particle transport system. See V. J. Novick, C. R. Hummer, and P. F. Dunn, “Minimum dc electric field requirements for removing powder layers from a conductive surface,” Journal of Applied Physics, Vol. 65, 3242-3247, 1989. Previous MEMS work only reported success on moving larger particles (over 30 &mgr;m) with voltages typically in the kV regime. See F. M. Moesner, T. Higuchi, “Devices for Particle Handling by an AC Electric Field,” IEEE Conference Proc. MEMS 1995.
SUMMARY
The present disclosure describes methods and apparatus implementing a technique for electrostatically transporting a particle through a medium. In general, one implementation includes a substrate; a first insulation layer formed on the substrate; a plurality of electrodes arranged in a sequence on the insulation layer, where the electrodes are divided into a plurality of groups and the electrodes are arranged by group; a second insulation layer over at least one of the electrodes; and a phase shift circuit connected to the electrodes which supplies a voltage wave-form to each group of electrodes, where each voltage wave-form for each group is phase-shifted relative to the other phase-shifted wave-forms.
The technique also includes generating a plurality of phase-shifted voltage wave-forms, each said voltage wave-form phase-shifted relative to each of the other phase-shifted voltage wave-forms; applying each phase-shifted voltage wave-form to a corresponding one of a plurality of electrodes to cause a particle to transport across the electrodes according to the phase-shifting, where the electrodes are arranged in sequential groups, each group including an electrode from each set in a sequence according to the phase-shift corresponding to that electrode, and where the particle is transported at a height over the electrodes between approximately 10 and 100% of the diameter of the particle.


REFERENCES:
patent: 3581462 (1971-06-01), Stump
patent: 4354861 (1982-10-01), Kalt
patent: 5582632 (1996-12-01), Nohr et al.
patent: 5593721 (1997-01-01), Daidai et al.

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