Nanotechnology - An Introduction

307 Pages·2011·4.44 MB·English

by  Ramsden

Nanotechnology: An
Introduction
Jeremy Ramsden
Cranfield University
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Preface
There are already hundreds of books in print on nanotechnology in English alone,
at all levels up to that of the advanced researcher and ranging in coverage from
detailedaccountsofincrementalimprovementsinexistingmicrotechnologiestofar-
reaching visionary approaches toward productive nanosystems. Furthermore, not
only do many old-established scientific journals in the fields of physics and chem-
istrynowcarrynanotechnologysections,butnumerousscientificjournalsdedicated
solely to nanotechnology have appeared and new ones are launched each year. In
addition, a flood of commercially oriented reports about present and future nano-
technologymarketsisconstantlybeingproduced;theseareoftenweightydocuments
comprising a thousand pages or more, whose reliability is difficult to assess, since
eveniftheymakeuseofpubliclyavailabledata,theprocessingofthosedatainorder
toarriveatpredictionsistypicallycarriedoutusingunrevealedalgorithms.
Faced with this huge and burgeoning literature, the newcomer to the field, who
may well have a strong background in one of the traditional disciplines such as
physics,mechanicalorelectricalengineering,chemistryorbiology,orwhomayhave
beenworkingonmicroelectromechanicalsystems(MEMS)(alsoknownasmicrosys-
tems technology, MST), is likely to feel confronted with a somewhat chaotic and
colorful scene from which it is often difficult to extract meaning. The goal of this
bookistotacklethatproblembypresentinganoverviewoftheentirefield,focusing
onkeyessentials,withwhichthereaderwillbeabletoerecthisorherownpersonal
scaffold on which the amazingly diverse plethora of detailed information emerging
from countless laboratories all over the world can be structured into some kind of
coherent order. The emphasis is therefore on concepts; any attempt to complement
thisbycapturingallthelatestspecificdiscoveriesandinventionsinnanotechnology,
other than illustratively, would almost immediately become out of date; the aim of
this book might briefly be stated as being “to make sense of nanotechnology”—to
explainthingsthoroughlyenoughtobeintelligiblewhilestillremainingintroductory.
Thebookitselfisstructuredaroundarobustanatomyofthesubject.Followinga
basicintroduction(Chapter1),whichincludesabriefhistoryofthesubject,careful
considerationisgiventothemeaningofthenanoscale(Chapter2),onwhichevery-
thing else is dependent, since nanotechnology can most simply (but cryptically) be
definedas“technology(orengineering)atthenanoscale”.Thischapterinitselfcon-
stitutes a succinct summary of the entire field. Chapter 3 is devoted to interfacial
forces, which govern key aspects of behavior at the nanoscale. Chapter 4 covers
the nano/bio interface, which plays a fundamental role in the continuing evolution
of nanotechnology, and Chapter 5 deals with the demanding issues of metrology
in nanotechnology, which have also strongly influenced nanofabrication technol-
ogy. In this chapter, the metrology of the nano/bio interface is covered in detail,
since this is one of the newest and least familiar parts of the field. Nanomaterials
(both nano-objects and nanostructured materials) are covered in Chapter 6—except
carbon nanomaterials (and devices), which merit a separate chapter (9). Nanoscale
xi
xii Preface
devices of all kinds (except those based on carbon)—mainly information proces-
sors and transducers, including sensors are the topic of Chapter 7, and strategies
for their fabrication are covered in Chapter 8, devoted to the three fundamental
approachestowardsachievingnanoscalemanufacture(nanofacture),namelythetop–
down methods rooted in ultraprecision engineering and semiconductor processing,
the bottom-to-bottom approach that is closest to the original concept of nanotech-
nology (the molecular assembler), and the bottom–up (self-assembly) methods that
havebeenpowerfullyinspiredbyprocessesinthelivingworld.Problemsofmaterials
selection,designandsofortharetreatedinChapter10,especiallyhowtodealwith
vastification;thatis,thevastnumbersofcomponentsinananosystemandthealmost
inevitable occurrence of defective ones. Chapter 11 is devoted to bionanotechnol-
ogy,definedastheincorporationofbiomoleculesintonanodevices.Thefinalchapter
(12)dealswiththeimpactsofnanotechnology:technical,economic,social,psycho-
logicalandethical.Eachchapterisprovidedwithasuccinctsummaryattheendas
wellassuggestionsforfurtherreading.Aglossaryofnanotechnologyneologismsis
appended,alongwithalistofthemostcommonabbreviations.
Theprimaryreadershipisexpectedtobeengineersandscientistswhohavepre-
viouslybeenworkinginotherfieldsbutareconsideringenteringthenanofieldand
wishtorapidlyacquireanappreciationofitsvocabulary,possibilitiesandlimitations.
Thesecondaryreadershipisanyonecuriousaboutnanotechnology,includingunder-
graduatesandprofessionalsinotherfields.Thebookshouldalsoappealtothoseless
directlyconnectedwithscienceandengineering,suchasinsurersandlawyers,whose
activities are very likely to be connected with nanotechnology in the future, and
traders, commodity brokers and entrepreneurs in general dissatisfied with remain-
inginignoranceofthetechnologythattheyaremakinguseof.Itisdesignedtoequip
thereaderwiththeabilitytocogentlyappraisethemeritsorotherwiseofanypiece
ofnanotechnologythatmaybereportedinoneformoranother.
It is a distinct characteristic of nanotechnology that many of its features draw
heavily from existing work in chemistry, physical chemistry, physics and biology.
Hence, there is relatively little domain-specific knowledge associated with nano-
technology.Mostofthethemesinthisbookarecoveredingreatdetailinspecialist
literature that may not exclusively or even overtly be associated with nanotechnol-
ogy.Itseems,therefore,thatnanotechnologyismostaptlygloballycharacterizedas
anattitudeormindset,comprisingaboveallthedesirebothtounderstandtheworld
at the atomic level and to create objects of beauty and utility by controlling matter
at that level. Unlike the science of the subatomic level, however, nanotechnology
necessarilyconcernsitselfwithsuperatomiclevelsaswell,sincetheultimateobjects
of its creation must be macroscopic in order to be of use to humanity. Hence,
problemsofemergentpropertiesalsoformapartofnanotechnology.
The uniqueness of this book resides in its unifying viewpoint that draws many
disparatepiecesofknowledgetogethertocreatenoveltechnologies.Thesenanotech-
nologiesareinturnunitedbythedistinctiveattitudeassociatedwithnanotechnology.
Nanotechnology is inseparably associated with the emergence of qualitatively
different behavior when a quantitative difference, namely increasing smallness,
Preface xiii
becomesgreatenough:onemightcallthisaHegelianviewpointofnanotechnology.
Phenomena that are merely modified pari passu with diminishing size without any
qualitativechangeshouldnot,therefore,strictlyrankasnanotechnology.Thisview-
point avoids the pitfall of having to group practically all of physics, chemistry and
biologyundernanotechnologybecauseoftoovagueadefinition.
Inevitably, the author of a book of this nature is greatly indebted to countless
colleaguesandcorrespondentsbothatCranfieldandthroughouttheworld.Itwould
beinvidioustomentionsomewithoutmentioningall,andtheyaretoonumerousfor
the latter, but I hope that in this era of a voluminous research literature their inputs
areadequatelyreflectedinthereferencelist.
JeremyJ.Ramsden
Cranfield
May2010
Contents
Preface .............................................................................. xi
CHAPTER 1 WhatisNanotechnology?....................................... 1
1.1 DefinitionsandConcepts........................................ 2
1.1.1 WorkingDefinitions...................................... 2
1.1.2 TowardsaConceptSystemforNanotechnology....... 3
1.2 AnOstensiveDefinitionofNanotechnology................... 5
1.3 ABriefHistoryofNanotechnology............................. 5
1.3.1 UltraprecisionEngineering.............................. 7
1.3.2 SemiconductorProcessingquaMicrotechnology...... 7
1.3.3 Nanoparticles............................................. 9
1.4 BiologyasParadigm............................................. 10
1.5 WhyNanotechnology? .......................................... 11
1.5.1 NovelCombinationsofProperties ...................... 11
1.5.2 DeviceMiniaturization:FunctionalEnhancement ..... 13
1.5.3 AUniversalFabricationTechnology.................... 14
1.6 Summary ......................................................... 14
CHAPTER 2 TheNanoscale................................................... 15
2.1 TheSizeofAtoms............................................... 17
2.2 MoleculesandSurfaces.......................................... 18
2.3 Nucleation........................................................ 20
2.4 ChemicalReactivity ............................................. 21
2.5 ElectronicandOpticalProperties ............................... 24
2.6 MagneticandFerroelectricProperties.......................... 27
2.7 MechanicalProperties ........................................... 28
2.8 QuantumSmallness.............................................. 30
2.9 Summary ......................................................... 33
CHAPTER 3 ForcesattheNanoscale ........................................ 35
3.1 TheCasimirForce ............................................... 36
3.2 IntermolecularInteractions...................................... 37
3.2.1 TheConceptofSurfaceTension ........................ 37
3.2.2 CritiqueoftheSurfaceTensionFormalism............. 41
3.2.3 ExperimentalDeterminationofSingle-Substance
SurfaceTensions......................................... 42
v
vi Contents
3.2.4 WettingandDewetting................................... 43
3.2.5 LengthScalesforDefiningSurfaceTension............ 44
3.2.6 TheWettingTransition .................................. 44
3.3 CapillaryForce................................................... 45
3.4 HeterogeneousSurfaces ......................................... 45
3.4.1 WettingonRoughandChemicallyInhomogeneous
Surfaces................................................... 46
3.4.2 Three-BodyInteractions................................. 47
3.5 WeakCompetingInteractions................................... 48
3.6 Cooperativity..................................................... 48
3.7 Percolation ....................................................... 49
3.8 TheStructureofWater........................................... 51
3.9 Summary ......................................................... 51
CHAPTER 4 TheNano/BioInterface.......................................... 53
4.1 The“Physical”Nano/BioInterface ............................. 55
4.1.1 Organisms ................................................ 56
4.1.2 Tissues.................................................... 56
4.1.3 Cells ...................................................... 57
4.1.4 Biomolecules............................................. 62
4.2 Nanomedicine.................................................... 64
4.2.1 AConceptSystemforNanomedicine................... 64
4.2.2 WiderImplications....................................... 68
4.3 Nanotoxicology.................................................. 68
4.4 Summary ......................................................... 70
CHAPTER 5 Nanometrology................................................... 73
5.1 Topography....................................................... 75
5.1.1 ContactMethods......................................... 75
5.1.2 Noncontact(Optical)Methods .......................... 79
5.2 ChemicalSurfaceStructure(Chemography) ................... 82
5.3 TheMetrologyofSelf-Assembly ............................... 84
5.4 TheRepresentationofTexture .................................. 85
5.4.1 Roughness................................................ 86
5.4.2 One-DimensionalTexture ............................... 87
5.4.3 Two-DimensionalTexture:Lacunarity.................. 91
5.5 MetrologyoftheNano/BioInterface ........................... 92
5.5.1 DeterminingtheNanostructureofProteinCoronas.... 92
5.5.2 MeasuringCellAdhesion:TheInteractionofan
EvanescentFieldwithaCell ............................ 93
Contents vii
5.5.3 OpticalMeasurementSchemes.......................... 95
5.5.4 ReverseWaveguides..................................... 96
5.5.5 TheInterpretationofEffectiveRefractiveIndex
Changes................................................... 97
5.5.6 TheInterpretationofCouplingPeakWidth
Changes................................................... 98
5.6 Summary ......................................................... 99
CHAPTER 6 NanomaterialsandtheirProduction ........................... 101
6.1 Nanoparticles..................................................... 103
6.1.1 ComminutionandDispersion ........................... 104
6.1.2 NucleationandGrowth.................................. 104
6.2 Nanofibers........................................................ 108
6.3 NanoplatesandUltrathinCoatings.............................. 108
6.3.1 MolecularBeamEpitaxy(MBE)........................ 109
6.3.2 LangmuirFilms .......................................... 109
6.3.3 Self-AssembledMonolayers(SAMs)................... 113
6.4 CrystallizationandSupramolecularChemistry................. 114
6.5 Composites....................................................... 115
6.5.1 Polymer–Nano-ObjectBlends........................... 116
6.5.2 Metal–MatrixComposites............................... 119
6.5.3 Self-RepairingComposites.............................. 120
6.5.4 NanofluidsforThermalTransport....................... 121
6.5.5 AlternatingPolyelectrolyteDeposition ................. 122
6.6 Summary ......................................................... 124
CHAPTER 7 Nanodevices ..................................................... 125
7.1 IssuesofMiniaturization ........................................ 127
7.2 DigitalInformationProcessing.................................. 129
7.3 QuantumComputing............................................. 133
7.4 ElectronicDevices............................................... 135
7.4.1 BallisticTransport........................................ 135
7.4.2 DepletionLayers......................................... 135
7.4.3 Single-ElectronDevices................................. 136
7.4.4 MolecularElectronicDevices........................... 140
7.4.5 QuantumDotCellularAutomata........................ 141
7.5 TrendsintheMiniaturizationofElectronics ................... 142
7.6 Spintronics(MagneticDevices)................................. 145
7.6.1 UltrasensitiveMagneticSensors ........................ 145
7.6.2 OtherMemoryDevices.................................. 146
viii Contents
7.6.3 Spin-DependentTransistors ............................. 147
7.6.4 SingleSpinLogic........................................ 147
7.7 PhotonicDevices................................................. 148
7.8 MechanicalDevices ............................................. 151
7.9 FluidicDevices................................................... 153
7.9.1 MixersandReactors ..................................... 156
7.9.2 ChemicalandBiochemicalSensors..................... 156
7.9.3 EnergyConversionDevices............................. 157
7.10 Summary ......................................................... 158
CHAPTER 8 NanofactureofDevices ......................................... 161
8.1 Top–DownMethods ............................................. 162
8.1.1 SemiconductorProcessing............................... 162
8.1.2 MismatchedEpitaxy..................................... 163
8.1.3 ElectrostaticSprayDeposition(ESD)................... 164
8.1.4 Felting .................................................... 164
8.1.5 UltraprecisionEngineering.............................. 165
8.2 Bottom–UpMethods............................................. 166
8.2.1 Self-Assembly............................................ 166
8.2.2 ThermodynamicsofSelf-Organization ................. 169
8.2.3 The“Goodness”oftheOrganization.................... 171
8.2.4 ParticleMixtures......................................... 171
8.2.5 MixedPolymers.......................................... 172
8.2.6 BlockCopolymers ....................................... 173
8.2.7 TheAdditionofParticlestotheSolid/Liquid
Interface .................................................. 174
8.2.8 ProgrammableSelf-Assembly........................... 178
8.2.9 Superspheres ............................................. 179
8.2.10 BiologicalSelf-Assembly ............................... 180
8.2.11 BiopolymerFolding...................................... 181
8.2.12 BiologicalGrowth ....................................... 182
8.2.13 Self-AssemblyasaManufacturingProcess ............ 183
8.3 Bottom-to-BottomMethods..................................... 184
8.3.1 Tip-BasedNanofabrication.............................. 185
8.3.2 Nanoblocks............................................... 186
8.3.3 DipPenNanolithography................................ 187
8.4 Summary ......................................................... 187
Contents ix
CHAPTER 9 Carbon-BasedNanomaterialsandDevices .................... 189
9.1 Graphene ......................................................... 191
9.2 CarbonNanotubes ............................................... 191
9.3 CarbonNanoparticles(Fullerenes).............................. 195
9.4 MaterialsApplications........................................... 195
9.5 DeviceComponentsandDevices ............................... 196
9.6 Summary ......................................................... 197
CHAPTER10 NanosystemsandtheirDesign.................................. 199
10.1 Systems........................................................... 199
10.2 Materialsselection............................................... 200
10.3 DefectsinNanograins ........................................... 202
10.4 SpacialDistributionofDefects.................................. 203
10.5 StrategiestoOvercomeComponentFailure.................... 204
10.6 ComputationalModeling........................................ 205
10.7 “Evolutionary”Design........................................... 206
10.8 PerformanceCriteria............................................. 208
10.9 Scaleout .......................................................... 209
10.10 Standardization................................................... 209
10.11 CreativeDesign.................................................. 210
10.12 Produceability.................................................... 210
10.13 Summary ......................................................... 211
CHAPTER11 Bionanotechnology .............................................. 213
11.1 TheStructuralNatureofBiomolecules......................... 215
11.2 SomeGeneralCharacteristicsofBiologicalMolecules........ 216
11.3 TheMechanismofBiologicalMachines ....................... 216
11.3.1 BiologicalMotors........................................ 218
11.3.2 MicrotubuleAssemblyandDisassembly............... 219
11.3.3 TheCostofControl...................................... 220
11.4 DNAasConstructionMaterial.................................. 221
11.5 Biosensors........................................................ 222
11.6 BiophotonicDevices............................................. 222
11.7 Summary ......................................................... 224
CHAPTER12 TheImpactofNanotechnology ................................. 227
12.1 TechnicalRevolutions ........................................... 229
12.2 ScientificImpacts................................................ 232