Biomedical Engineering Reference
In-Depth Information
17
Dielectrop
horesis
Shiqing Wu and Shengnian Wang
CONTENTS
17.1. Introduction......................................................................................................................... 393
17.2. Working.Mechanism.of.DEP............................................................................................ 394
17.2.1. Derivation.of.DEP.Force........................................................................................ 395
17.2.2. Key.Factors.in.DEP................................................................................................. 396
17.2.2.1. Clausius-Mossotti.Factor....................................................................... 396
17.2.2.2. Particles.with.Heterogeneous.Structure.............................................. 398
17.2.2.3. Electric.Field.Gradient............................................................................. 399
17.3. DEP.Electrode.Designs.and.Derivates............................................................................ 400
17.3.1. Castellated.Electrode.Structures.and.Their.Derivates...................................... 400
17.3.2. Quadruple.Electrode.Structure............................................................................ 402
17.3.3. Electrodeless.DEP................................................................................................... 404
17.3.4. Optoelectronic.Tweezers....................................................................................... 405
17.4. DEP.Applications................................................................................................................ 406
17.4.1. DEP.Trapping.for.High-Throughput.Separation............................................... 406
17.4.2. DEP.Trapping.for.Particle.Positioning................................................................ 408
17.4.3. DEP.Levitation.for.Particle.Delection................................................................. 408
17.4.4. DEP.Levitation.for.Particle.Concentration.and.Focusing................................. 410
17.4.5. DEP-Based.Field.Flow.Fractionation................................................................... 411
17.4.6. DEP.for.Electrorotation.and.Transportation...................................................... 413
17.4.7. DEP.Manipulation.by.OET.................................................................................... 416
17.5. Concluding.Remarks.and.Perspectives........................................................................... 416
References..................................................................................................................................... 417
17.1 Introduction
In. the. presence. of. an. external. electric. ield,. particles. may. move. by. electrophoresis. (EP,.
the. Coulomb. force. driven. motions. for. charged. particles),. electroosmosis. (EO,. the. low.
induced. motions. due. to. the. charged. solid. surface),. dielectrophoresis. (DEP,. the. electric.
ield. gradient. induced. particle. motions),. or. their. combinations.. Unlike. in. EP,. motions.
triggered.by.DEP.are.not.limited.to.charged.particles..The.intense.electric.ield.gradient.
around. DEP. electrodes. can. induce. a. dipole. moment. between. a. neutral. particle. and. its.
surrounding.medium,.namely,.the.Maxwell-Wagner.interfacial.polarization,.to.regulate.
movements. of. the. particle. (Figure. 17.1a. and. b).. This. phenomenon. was. irst. discovered.
by.Dr..Herbert.Pohl.from.Princeton.University.when.he.studied.the.suspension.of.water.
393
