Biomedical Engineering Reference
In-Depth Information
devices..For.more.information,.please.refer.to.some.excellent.review.articles.on.this.ield.
(Tegenfeldt.et.al..2004;.Mijatovic.et.al..2005).
Fabrication. of. nanoluidic. devices. is. usually. more. complicated. than. that. of. micro-
luidic. devices.. First. of. all,. size. does. matter. because. a. nanoluidic. device. is. smaller,.
and. thus. complicated. fabrication. techniques. are. needed.. Second,. unlike. microluidic.
devices,.which.do.not.necessarily.need.to.be.parallelized.to.achieve.mass.production,.
nanoluidic. devices. usually. cannot. generate. a. desirable. quantity. of. products. unless. a.
large. scale. of. parallelization. can. be. realized.. Thus,. a. nanoluidic. device. usually. has.
many. parallel. channels. and. requires. special. methods. and. more. time. in. fabrication..
Third,.in.many.biomedical.applications,.organic.or.polymer-based.nanoluidic.devices.
are.more.favorable.due.to.the.requirement.of.biocompatibility,.cost-eficiency,.and.dis-
posability..However,.polymeric.nanoluidic.devices.are.dificult.to.fabricate.and.novel.
techniques.are.always.necessary..Fourth,.since.a.usable.nanoluidic.device.needs.to.be.
integrated.with.micro-.or.even.macroscaled.units.such.as.reservoirs,.there.is.always.a.
micro-/nanoscaled. interface,. and. thus,. different. fabrication. methods. are. required. to.
integrate.different.units.in.such.a.multiscale.system..Finally,.bonding.and.sealing.the.
nanoluidic.device.is.not.trivial.at.all..It.involves.many.complicated.processes.(Mijatovic.
et.al..2005).
From. the. scale. point. of. view,. there. are. typically. two. approaches. to. fabricate. nanolu-
idic.devices,.i.e.,.top-down.and.bottom-up.approaches..The.top-down.approach.fabricates.
small-scaled.nanostructures.with.existing.large-scaled.patterns..It.usually.uses.expensive.
clean-room.technologies.such.as.electron-beam.lithography.(EBL),.focused.ion.beam.(FIB).
lithography,.pulsed-laser.deposition.(PLD),.and.nanoimprint.lithography.(NIL),.especially.
in.fabricating.a.large.scale.of.well-deined.nanostructures.
The. bottom-up. approach. generally. builds. up. nanostructures. with. atoms. or. molecules.
via. self-assembly.. This. approach. is. usually. a. non-clean-room. technology. and. does. not.
require. expensive. equipments. and. complicated. processes.. It. has. been. used. to. fabricate.
carbon. nanotubes,. quantum. dots,. self-assembled. monolayers. (SAM),. bilayer. lipid.
membranes. (BLM),. and. ion-channel. nanopores.. Self-assembly. is. usually. a. slow. process.
since. the. system. is. near. the. state. of. thermodynamic. equilibrium. and. nanostructures.
are. created. in. atom-by-atom. or. molecule-by-molecule. way.. Most. recently,. a. much. faster.
low-guided. assembly. that. uses. capillary. or. hydrodynamic. forces. has. been. reported. to.
create.well-deined.large-scaled.nanostructures.(Brinker.2004;.Yuan.et.al..2006;.Wang.et.al..
2008b)..Field-guide.assembly.methods.using.spatially.periodical.or.nonuniform.electric.or.
magnetic.ields.can.also.be.applied.to.fabricate.large-scale.nanostructures.
Top-down. and. bottom-up. approaches. can. be. combined. together. to. create. novel. and.
inexpensive.nanoluidic.devices..For.example,.a.polymeric.nanonozzle.array.can.be.irst.
fabricated.using.the.sacriicial.template.imprinting.(STI).techniques.(Wang.et.al..2004)..In.
order.to.reduce.the.nozzle.size,.bottom-up.approach.with.EOF-based.dynamic.assembly.
is. used. to. grow. silica. on. the. internal. surface. of. the. nanonozzle.. Another. example.
involves.a.DNA.combing.and.imprinting.(DCI).technique.(Guan.et.al..2010)..As.shown.
in.Figure.18.1,.ordered.DNA.nanowire.arrays.are.irst.created.through.a.DNA.combing.
technique.on.patterned.micro-.or.nanopillar.arrays..This.special.bottom-up.approach.of.
fabricating. DNA. nanowire. arrays. is. a. low-guided. assembly. with. receding. meniscus..
Then,. DNA. nanowires. are. coated. with. gold. to. form. more. rigid. nanostrands.. Next. is.
the.imprinting.technique.of.transferring.nanopatterns.to.EGDMA.polymer.resin..After.
etching. the. gold-coated. nanostrands,. well-deined. nanochannel. and. microwell. arrays.
are. inally. produced.. Top-down. micromachining. can. be. further. carried. out. to. make.
extra.microgroove.structures.
