Biomedical Engineering Reference
In-Depth Information
19
Optical Tw
eezers
Yingbo Zu, Fangfang Ren, and Shengnian Wang
CONTENTS
19.1. Introduction......................................................................................................................... 439
19.2. Optical.Trap.Mechanism................................................................................................... 440
19.2.1. Optical.Trapping.in.Mie.Scattering.Regime....................................................... 440
19.2.2. Optical.Trapping.in.Raleigh.Scattering.Regime................................................ 441
19.2.3. Optical.Trapping.for.Intermediate.Size.Particles.............................................. 443
19.3. Optical.Trap.Instrument.and.Design..............................................................................443
19.3.1. General.Optical.Trap.Setup.................................................................................. 443
19.3.2. Major.Components.of.Optical.Trap.and.Their.
Current.Emerging.Techniques............................................................................. 443
19.3.2.1. Trapping.Laser......................................................................................... 443
19.3.2.2. Single.Beam.and.Dual.Beam.................................................................. 446
19.3.2.3. Time.Sharing.Multiple.Trapping........................................................... 447
19.4. Optical.Tweezers.Applications.in.Life.Science.............................................................. 448
19.4.1. Biomechanics........................................................................................................... 448
19.4.1.1. DNA.and.RNA.Mechanics..................................................................... 448
19.4.1.2. Mechanics.of.Other.Biomolecules......................................................... 451
19.4.1.3. Mechanics.of.Molecular.Motors............................................................ 451
19.4.2. Cell.Related.Study.................................................................................................. 452
19.4.2.1. Trapping.and.Positioning....................................................................... 452
19.4.2.2. Sorting.and.Separation........................................................................... 452
19.4.2.3. Assembling.and.Surgery........................................................................ 455
19.5. Concluding.Remarks,.Improvements,.and.Perspectives.............................................. 455
References..................................................................................................................................... 457
19.1 Introduction
Similar.to.dielectrophoresis,.an.optical.trap.also.occurs.in.the.presence.of.a.highly.non-
uniform. ield.. But. this. time,. the. large. ield. gradient. is. generated. by. a. highly. focused.
laser.beam.(Ashkin.et.al..1987,.2007)..Unlike.other.trapping.technologies,.an.optical.trap.
does. not. require. physical. contact. with. the. target. object,. and. therefore,. it. is. favorable. in.
many.applications.involving.live.systems..The.apparatus.for.an.optical.trap,.namely.opti-
cal.tweezers,.has.been.broadly.used.to.trap.and.manipulate.microspheres,.molecules,.or.
organelles.inside.cells.and.cells.themselves.(e.g.,.bacteria,.yeasts,.and.mammalian.cells)..
Most.of.these.objects.have.a.size.of.0.1-10.λ.of.the.applied.laser.beam.(note:.λ.is.the.laser.
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