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ISBN 0 85403 604 0
The Royal Society 2004
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Contents
page
Summary vii
1 Introduction 11.1 Hopes and concerns about nanoscience and
nanotechnologies 11.2 Terms of reference and conduct of the study
21.3 Report overview 21.4 Next steps 3
2 What are nanoscience and nanotechnologies? 5
3 Science and applications 73.1 Introduction 73.2 Nanomaterials
7
3.2.1 Introduction to nanomaterials 73.2.2 Nanoscience in this
area 83.2.3 Applications 10
3.3 Nanometrology 133.3.1 Introduction to nanometrology 133.3.2
Length measurement 133.3.3 Force measurement 143.3.4 Measurement of
single molecules 143.3.5 Applications 14
3.4 Electronics, optoelectronics, and information and
communication technology (ICT) 173.4.1 Introduction to electronics,
optoelectronics, and ICT 173.4.2 Nanoscience in this area 173.4.3
Current applications 173.4.4 Applications anticipated in the future
18
3.5 Bio-nanotechnology and nanomedicine 193.5.1 Introduction to
bio-nanotechnology and nanomedicine 193.5.2 Nanoscience in this
area 203.5.3 Current and future applications 20
4 Nanomanufacturing and the industrial application of
nanotechnologies 254.1 Introduction 254.2 Characterisation 254.3
Fabrication techniques 25
4.3.1 Bottom-up manufacturing 264.3.2 Top-down manufacturing
284.3.3 Convergence of top-down and bottom-up techniques 29
4.4 Visions for the future 304.4.1 Precision Engineering 304.4.2
The chemicals industry 314.4.3 The information and communication
technology industry 31
4.5 Resource management and environmental issues 324.6 Barriers
to progress 324.7 Summary 33
Nanoscience and nanotechnologies: opportunities and
uncertainties
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5 Possible adverse health, environmental and safety impacts
355.1 Introduction 355.2 Assessing and controlling risk 355.3 Human
health 36
5.3.1 Understanding the toxicity of nanoparticles and fibres
365.3.2 Manufactured nanoparticles and nanotubes 41
5.4 Effects on the environment and other species 455.5 Risk of
explosion 475.6 Addressing the knowledge gaps 475.7 Conclusions
49
6 Social and ethical issues 516.1 Introduction: framing social
and ethical issues 516.2 Economic impacts 526.3 A nanodivide? 526.4
Information collection and the implications for civil liberties
536.5 Human enhancement 546.6 Covergence 546.7 Military uses 556.8
Conclusions 56
7 Stakeholder and public dialogue 597.1 Introduction 597.2
Current public awareness of nanotechnologies in Britain 59
7.2.1 Quantitative survey findings 597.2.2 Qualitative workshop
findings 607.2.3 Interpreting the research into public attitudes
61
7.3 Importance of promoting a wider dialogue 627.4
Nanotechnologies as an upstream issue 647.5 Designing dialogue on
nanotechnologies 64
7.5.1 Incorporating public values in decisions 667.5.2 Improving
decision quality 667.5.3 Resolving conflict 667.5.4 Improving trust
in institutions 667.5.5 Informing or educating people 66
7.6 Conclusions 67
8 Regulatory issues 698.1 Introduction 698.2 Approaches to
regulation 698.3 Case studies 70
8.3.1 Workplace (including research laboratories) 708.3.2
Marketing and use of chemicals 718.3.3 Consumer products
incorporating free nanoparticles, particularly skin preparations
728.3.4 Medicines and medical devices 748.3.5 Consumer products
incorporating fixed nanoparticles: end-of-life issues 74
8.4 Knowledge gaps 748.4.1 Hazard 748.4.2 Exposure 758.4.3
Measurement 75
8.5 Conclusions 76
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9 Conclusions 799.1 Nanoscience and nanotechnologies and their
industrial application 799.2 Health, safety and environmental risks
and hazards 799.3 Social and ethical impacts 819.4 Stakeholder and
public dialogue 819.5 Regulation 829.6 Responsible development of
nanotechnologies 839.7 A mechanism for addressing future issues
84
10 Recommendations 85
11 References 89
Annexes
A Working Group, Review Group and Secretariat 95
B Conduct of the study 97
C List of those who submitted evidence 99
D Mechanical self-replicating nano-robots and Grey Goo 109
Acronyms and abbreviations 111
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Summary
Overview
1 Nanoscience and nanotechnologies are widely seenas having huge
potential to bring benefits to many areasof research and
application, and are attracting rapidlyincreasing investments from
Governments and frombusinesses in many parts of the world. At the
same time,it is recognised that their application may raise
newchallenges in the safety, regulatory or ethical domainsthat will
require societal debate. In June 2003 the UKGovernment therefore
commissioned the Royal Societyand the Royal Academy of Engineering
to carry out thisindependent study into current and future
developmentsin nanoscience and nanotechnologies and their
impacts.
2 The remit of the study was to:
define what is meant by nanoscience andnanotechnologies;
summarise the current state of scientific knowledgeabout
nanotechnologies;
identify the specific applications of the newtechnologies, in
particular where nanotechnologies arealready in use;
carry out a forward look to see how the technologiesmight be
used in future, where possible estimating thelikely timescales in
which the most far-reachingapplications of the technologies might
become reality;
identify what health and safety, environmental, ethicaland
societal implications or uncertainties may arisefrom the use of the
technologies, both current andfuture; and
identify areas where additional regulation needs to
beconsidered.
3 In order to carry out the study, the two Academiesset up a
Working Group of experts from the relevantdisciplines in science,
engineering, social science andethics and from two major public
interest groups. Thegroup consulted widely, through a call for
writtenevidence and a series of oral evidence sessions andworkshops
with a range of stakeholders from both theUK and overseas. It also
reviewed published literatureand commissioned new research into
public attitudes.Throughout the study, the Working Group
hasconducted its work as openly as possible and haspublished the
evidence received on a dedicated websiteas it became available
(www.nanotec.org.uk).
4 This report has been reviewed and endorsed by theRoyal Society
and the Royal Academy of Engineering.
Significance of the nanoscale
5 A nanometre (nm) is one thousand millionth of ametre. For
comparison, a single human hair is about80,000 nm wide, a red blood
cell is approximately 7,000nm wide and a water molecule is almost
0.3nm across.People are interested in the nanoscale (which we
defineto be from 100nm down to the size of atoms(approximately
0.2nm)) because it is at this scale thatthe properties of materials
can be very different fromthose at a larger scale. We define
nanoscience as thestudy of phenomena and manipulation of materials
atatomic, molecular and macromolecular scales, whereproperties
differ significantly from those at a largerscale; and
nanotechnologies as the design,characterisation, production and
application ofstructures, devices and systems by controlling shape
andsize at the nanometre scale. In some senses,nanoscience and
nanotechnologies are not new.Chemists have been making polymers,
which are largemolecules made up of nanoscale subunits, for
manydecades and nanotechnologies have been used tocreate the tiny
features on computer chips for the past20 years. However, advances
in the tools that now allowatoms and molecules to be examined and
probed withgreat precision have enabled the expansion
anddevelopment of nanoscience and nanotechnologies.
6 The properties of materials can be different at thenanoscale
for two main reasons. First, nanomaterials havea relatively larger
surface area when compared to thesame mass of material produced in
a larger form. This canmake materials more chemically reactive (in
some casesmaterials that are inert in their larger form are
reactivewhen produced in their nanoscale form), and affect
theirstrength or electrical properties. Second, quantum effectscan
begin to dominate the behaviour of matter at thenanoscale -
particularly at the lower end - affecting theoptical, electrical
and magnetic behaviour of materials.Materials can be produced that
are nanoscale in onedimension (for example, very thin surface
coatings), intwo dimensions (for example, nanowires and
nanotubes)or in all three dimensions (for example,
nanoparticles).
7 Our wide-ranging definitions cut across manytraditional
scientific disciplines. The only featurecommon to the diverse
activities characterised asnanotechnology is the tiny dimensions on
which theyoperate. We have therefore found it more appropriateto
refer to nanotechnologies.
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Current and potential uses of nanoscienceand
nanotechnologies
8 Our aim has been to provide an overview of currentand
potential future developments in nanoscience andnanotechnologies
against which the health, safety,environmental, social and ethical
implications can beconsidered. We did not set out to identify areas
ofnanoscience and nanotechnologies that should beprioritised for
funding.
(i) Nanomaterials
9 Much of nanoscience and many nanotechnologiesare concerned
with producing new or enhanced materi-als. Nanomaterials can be
constructed by 'top down'techniques, producing very small
structures from largerpieces of material, for example by etching to
create cir-cuits on the surface of a silicon microchip. They
mayalso be constructed by 'bottom up' techniques, atomby atom or
molecule by molecule. One way of doingthis is self-assembly, in
which the atoms or moleculesarrange themselves into a structure due
to their naturalproperties. Crystals grown for the semiconductor
indus-try provide an example of self assembly, as does chemi-cal
synthesis of large molecules. A second way is to usetools to move
each atom or molecule individually.Although this positional
assembly offers greater con-trol over construction, it is currently
very laborious andnot suitable for industrial applications.
10 Current applications of nanoscale materials includevery thin
coatings used, for example, in electronics andactive surfaces (for
example, self-cleaning windows). Inmost applications the nanoscale
components will befixed or embedded but in some, such as those used
incosmetics and in some pilot environmental
remediationapplications, free nanoparticles are used. The ability
tomachine materials to very high precision and accuracy(better than
100nm) is leading to considerable benefitsin a wide range of
industrial sectors, for example in theproduction of components for
the information andcommunication technology (ICT), automotive and
aero-space industries.
11 It is rarely possible to predict accurately thetimescale of
developments, but we expect that in thenext few years nanomaterials
will provide ways ofimproving performance in a range of products
includingsilicon-based electronics, displays, paints,
batteries,micro-machined silicon sensors and catalysts. Furtherinto
the future we may see composites that exploit theproperties of
carbon nanotubes rolls of carbon withone or more walls, measuring a
few nanometres indiameter and up to a few centimetres in length
whichare extremely strong and flexible and can conductelectricity.
At the moment the applications of thesetubes are limited by the
difficulty of producing them in auniform manner and separating them
into individualnanotubes. We may also see lubricants based on
inorganic nanospheres; magnetic materials usingnanocrystalline
grains; nanoceramics used for moredurable and better medical
prosthetics; automotivecomponents or high-temperature furnaces; and
nano-engineered membranes for more energy-efficient
waterpurification.
(ii) Metrology
12 Metrology, the science of measurement, underpinsall other
nanoscience and nanotechnologies because itallows the
characterisation of materials in terms ofdimensions but also in
terms of attributes such as elec-trical properties and mass.
Greater precision in metrolo-gy will assist the development of
nanoscience and nan-otechnologies. However, this will require
increased stan-dardisation to allow calibration of equipment and
werecommend that the Department of Trade and Industryensure that
this area is properly funded.
(iii) Electronics, optoelectronics and ICT
13 The role of nanoscience and nanotechnologies inthe
development of information technology is anticipat-ed in the
International Technology Roadmap forSemiconductors, a worldwide
consensus document thatpredicts the main trends in the
semiconductor industryup to 2018. This roadmap defines a
manufacturingstandard for silicon chips in terms of the length of
aparticular feature in a memory cell. For 2004 the stan-dard is 90
nm, but it is predicted that by 2016 this willbe just 22 nm. Much
of the miniaturisation of computerchips to date has involved
nanoscience and nanotech-nologies, and this is expected to continue
in the shortand medium term. The storage of data, using optical
ormagnetic properties to create memory, will also dependon advances
in nanoscience and nanotechnologies.
14 Alternatives to silicon-based electronics are alreadybeing
explored through nanoscience andnanotechnologies, for example
plastic electronics forflexible display screens. Other nanoscale
electronicdevices currently being developed are sensors to
detectchemicals in the environment, to check the edibility
offoodstuffs, or to monitor the state of mechanicalstresses within
buildings. Much interest is also focusedon quantum dots,
semiconductor nanoparticles that canbe tuned to emit or absorb
particular light colours foruse in solar energy cells or
fluorescent biological labels.
(iv) Bionanotechnology and nanomedicine
15 Applications of nanotechnologies in medicine areespecially
promising, and areas such as disease diagno-sis, drug delivery
targeted at specific sites in the bodyand molecular imaging are
being intensively investigat-ed and some products are undergoing
clinical trials.Nanocrystalline silver, which is known to have
antimi-crobial properties, is being used in wound dressings inthe
USA. Applications of nanoscience and nanotech-
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Nanoscience and nanotechnologies | July 2004 | ix
nologies are also leading to the production of materialsand
devices such as scaffolds for cell and tissue engi-neering, and
sensors that can be used for monitoringaspects of human health.
Many of the applications maynot be realised for ten years or more
(owing partly tothe rigorous testing and validation regimes that
will berequired). In the much longer term, the development
ofnanoelectronic systems that can detect and processinformation
could lead to the development of an artifi-cial retina or cochlea.
Progress in the area of bionan-otechnology will build on our
understanding of naturalbiological structures on the molecular
scale, such asproteins.
(v) Industrial applications
16 So far, the relatively small number of applications
ofnanotechnologies that have made it through toindustrial
application represent evolutionary rather thanrevolutionary
advances. Current applications are mainlyin the areas of
determining the properties of materials,the production of
chemicals, precision manufacturingand computing. In mobile phones
for instance, materialsinvolving nanotechnologies are being
developed for usein advanced batteries, electronic packaging and
indisplays. The total weight of these materials willconstitute a
very small fraction of the whole product butbe responsible for most
of the functions that the devicesoffer. In the longer term, many
more areas may beinfluenced by nanotechnologies but there will
besignificant challenges in scaling up production from theresearch
laboratory to mass manufacturing.
17 In the longer term it is hoped thatnanotechnologies will
enable more efficient approachesto manufacturing which will produce
a host of multi-functional materials in a cost-effective manner,
withreduced resource use and waste. However, it isimportant that
claims of likely environmental benefitsare assessed for the entire
lifecycle of a material orproduct, from its manufacture through its
use to itseventual disposal. We recommend that lifecycleassessments
be undertaken for applications ofnanotechnologies.
18 Hopes have been expressed for the developmentand use of
mechanical nano-machines which would becapable of producing
materials (and themselves) atom-by-atom (however this issue was not
raised by theindustrial representatives to whom we spoke).
Alongsidesuch hopes for self-replicating machines, fears havebeen
raised about the potential for these (as yetunrealised) machines to
go out of control, produceunlimited copies of themselves, and
consume allavailable material on the planet in the process (the
socalled grey goo scenario). We have concluded thatthere is no
evidence to suggest that mechanical self-replicating nanomachines
will be developed in theforeseeable future.
Health and environmental impacts
19 Concerns have been expressed that the veryproperties of
nanoscale particles being exploited incertain applications (such as
high surface reactivity andthe ability to cross cell membranes)
might also havenegative health and environmental impacts.
Manynanotechnologies pose no new risks to health andalmost all the
concerns relate to the potential impacts ofdeliberately
manufactured nanoparticles and nanotubesthat are free rather than
fixed to or within a material.Only a few chemicals are being
manufactured innanoparticulate form on an industrial scale
andexposure to free manufactured nanoparticles andnanotubes is
currently limited to some workplaces(including academic research
laboratories) and a smallnumber of cosmetic uses. We expect the
likelihood ofnanoparticles or nanotubes being released fromproducts
in which they have been fixed or embedded(such as composites) to be
low but have recommendedthat manufacturers assess this potential
exposure riskfor the lifecycle of the product and make their
findingsavailable to the relevant regulatory bodies.
20 Few studies have been published on the effects ofinhaling
free manufactured nanoparticles and we havehad to rely mainly on
analogies with results from studieson exposure to other small
particles such as thepollutant nanoparticles known to be present in
largenumbers in urban air, and the mineral dusts in someworkplaces.
The evidence suggests that at least somemanufactured nanoparticles
will be more toxic per unitof mass than larger particles of the
same chemical. Thistoxicity is related to the surface area of
nanoparticles(which is greater for a given mass than that of
largerparticles) and the chemical reactivity of the surface(which
could be increased or decreased by the use ofsurface coatings). It
also seems likely that nanoparticleswill penetrate cells more
readily than larger particles.
21 It is very unlikely that new manufacturednanoparticles could
be introduced into humans in dosessufficient to cause the health
effects that have beenassociated with the nanoparticles in polluted
air.However, some may be inhaled in certain workplaces
insignificant amounts and steps should be taken tominimise
exposure. Toxicological studies haveinvestigated nanoparticles of
low solubility and lowsurface activity. Newer nanoparticles with
characteristicsthat differ substantially from these should be
treatedwith particular caution. The physical characteristics
ofcarbon and other nanotubes mean that they may havetoxic
properties similar to those of asbestos fibres,although preliminary
studies suggest that they may notreadily escape into the air as
individual fibres. Untilfurther toxicological studies have been
undertaken,human exposure to airborne nanotubes in laboratoriesand
workplaces should be restricted.
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22 If nanoparticles penetrate the skin they might facil-itate
the production of reactive molecules that couldlead to cell damage.
There is some evidence to showthat nanoparticles of titanium
dioxide (used in somesun protection products) do not penetrate the
skin butit is not clear whether the same conclusion holds
forindividuals whose skin has been damaged by sun or bycommon
diseases such as eczema. There is insufficientinformation about
whether other nanoparticles used incosmetics (such as zinc oxide)
penetrate the skin andthere is a need for more research into this.
Much of theinformation relating to the safety of these
ingredientshas been carried out by industry and is not published
inthe open scientific literature. We therefore recommendthat the
terms of reference of safety advisory commit-tees that consider
information on the toxicology ofingredients such as nanoparticles
include a requirementfor relevant data, and the methodologies used
toobtain them, to be placed in the public domain.
23 Important information about the fate and behav-iour of
nanoparticles that penetrate the bodys defencescan be gained from
researchers developing nanoparti-cles for targeted drug delivery.
We recommend collabo-ration between these researchers and those
investigat-ing the toxicity of other nanoparticles and nanotubes.In
addition, the safety testing of these novel drug deliv-ery methods
must consider the toxic properties specificto such particles,
including their ability to affect cellsand organs distant from the
intended target of thedrug.
24 There is virtually no information available about theeffect
of nanoparticles on species other than humans orabout how they
behave in the air, water or soil, orabout their ability to
accumulate in food chains. Untilmore is known about their
environmental impact weare keen that the release of nanoparticles
and nan-otubes to the environment is avoided as far as
possible.Specifically, we recommend as a precautionary measurethat
factories and research laboratories treat manufac-tured
nanoparticles and nanotubes as if they were haz-ardous and reduce
them from waste streams and thatthe use of free nanoparticles in
environmental applica-tions such as remediation of groundwater be
prohibit-ed.
25 There is some evidence to suggest that com-bustible
nanoparticles might cause an increased risk ofexplosion because of
their increased surface area andpotential for enhanced reaction.
Until this hazard hasbeen properly evaluated this risk should be
managed bytaking steps to avoid large quantities of these
nanopar-ticles becoming airborne.
26 Research into the hazards and exposure pathwaysof
nanoparticles and nanotubes is required to reducethe many
uncertainties related to their potentialimpacts on health, safety
and the environment. Thisresearch must keep pace with the future
development
of nanomaterials. We recommend that the UK ResearchCouncils
assemble an interdisciplinary centre (perhapsfrom existing research
institutions) to undertakeresearch into the toxicity, epidemiology,
persistence andbioaccumulation of manufactured nanoparticles
andnanotubes, to work on exposure pathways and todevelop
measurement methods. The centre should liaiseclosely with
regulators and with other researchers in theUK, Europe and
internationally. We estimate that fund-ing of 5-6M pa for 10 years
will be required. Corefunding should come from the Government but
thecentre would also take part in European and interna-tionally
funded projects.
Social and ethical impacts
27 If it is difficult to predict the future direction
ofnanoscience and nanotechnologies and the timescaleover which
particular developments will occur, it is evenharder to predict
what will trigger social and ethicalconcerns. In the short to
medium term concerns areexpected to focus on two basic questions:
Whocontrols uses of nanotechnologies? and Who benefitsfrom uses of
nanotechnologies?. These questions arenot unique to
nanotechnologies but past experiencewith other technologies
demonstrates that they willneed to be addressed.
28 The perceived opportunities and threats ofnanotechnologies
often stem from the samecharacteristics. For example, the
convergence ofnanotechnologies with information technology,
linkingcomplex networks of remote sensing devices withsignificant
computational power, could be used toachieve greater personal
safety, security andindividualised healthcare and to allow
businesses totrack and monitor their products. It could equally
beused for covert surveillance, or for the collection
anddistribution of information without adequate consent.As new
forms of surveillance and sensing are developed,further research
and expert legal analysis might benecessary to establish whether
current regulatoryframeworks and institutions provide
appropriatesafeguards to individuals and groups in society. In
themilitary context, too, nanotechnologies hold potentialfor both
defence and offence and will therefore raise anumber of social and
ethical issues.
29 There is speculation that a possible futureconvergence of
nanotechnologies with biotechnology,information and cognitive
sciences could be used forradical human enhancement. If these
possibilities wereever realised they would raise profound
ethicalquestions.
30 A number of the social and ethical issues thatmight be
generated by developments in nanoscienceand nanotechnologies should
be investigated furtherand we recommend that the research councils
and the
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Arts and Humanities Research Board fund amultidisciplinary
research programme to do this. Wealso recommend that the ethical
and social implicationsof advanced technologies form part of the
formaltraining of all research students and staff working inthese
areas.
Stakeholder and public dialogue
31 Public attitudes can play a crucial role in realisingthe
potential of technological advances. Public aware-ness of
nanotechnologies is low in Great Britain. In thesurvey of public
opinion that we commissioned, only29% said they had heard of
nanotechnology and only19% could offer any form of definition. Of
those whocould offer a definition, 68% felt that it would
improvelife in the future, compared to only 4% who thought itwould
make life worse.
32 In two in-depth workshops involving small groupsof the
general public, participants identified bothpositive and negative
potentials in nanotechnologies.Positive views were expressed about
new advances in anexciting field; potential applications
particularly inmedicine; the creation of new materials; a sense
thatthe developments were part of natural progress and thehope that
they would improve the quality of life.Concerns were about
financial implications; impacts onsociety; the reliability of new
applications; long-termside-effects and whether the technologies
could becontrolled. The issue of the governance ofnanotechnologies
was also raised. Which institutionscould be trusted to ensure that
the trajectories ofdevelopment of nanotechnologies are
sociallybeneficial? Comparisons were made with geneticallymodified
organisms and nuclear power.
33 We recommend that the research councils buildupon our
preliminary research into public attitudes byfunding a more
sustained and extensive programmeinvolving members of the general
public and membersof interested sections of society.
34 We believe that a constructive and proactive debateabout the
future of nanotechnologies should beundertaken now at a stage when
it can inform keydecisions about their development and before
deeplyentrenched or polarised positions appear. Werecommend that
the Government initiate adequatelyfunded public dialogue around the
development ofnanotechnologies. The precise method of dialogue
andchoice of sponsors should be designed around theagreed
objectives of the dialogue. Our public attitudeswork suggests that
governance would be anappropriate subject for initial dialogue and
given thatthe Research Councils are currently funding researchinto
nanotechnologies they should consider taking thisforward.
Regulation
35 A key issue arising from our discussions with thevarious
stakeholders was how society can control thedevelopment and
deployment of nanotechnologies tomaximise desirable outcomes and
keep undesirableoutcomes to an acceptable minimum in other
words,how nanotechnologies should be regulated. Theevidence
suggests that at present regulatoryframeworks at EU and UK level
are sufficiently broadand flexible to handle nanotechnologies at
their currentstage of development. However some regulations
willneed to be modified on a precautionary basis to reflectthe fact
that the toxicity of chemicals in the form of freenanoparticles and
nanotubes cannot be predicted fromtheir toxicity in a larger form
and that in some casesthey will be more toxic than the same mass of
the samechemical in larger form. We looked at a small number
ofareas of regulation that cover situations where exposureto
nanoparticles or nanotubes is likely currently or in thenear
future.
36 Currently the main source of inhalation exposure
tomanufactured nanoparticles and nanotubes is inlaboratories and a
few other workplaces. Werecommend that the Health and Safety
Executive carryout a review of the adequacy of existing regulation
toassess and control workplace exposure to nanoparticlesand
nanotubes including those relating to accidentalrelease. In the
meantime they should consider settinglower occupational exposure
levels for chemicals whenproduced in this size range.
37 Under current UK chemical regulation (Notificationof New
Substances) and its proposed replacement beingnegotiated at
European level (Registration, Evaluationand Authorisation of
Chemicals) the production of anexisting substance in
nanoparticulate form does nottrigger additional testing. We
recommend thatchemicals produced in the form of nanoparticles
andnanotubes be treated as new chemicals under theseregulatory
frameworks. The annual productionthresholds that trigger testing
and the testingmethodologies relating to substances in these
sizes,should be reviewed as more toxicological evidencebecomes
available.
38 Under cosmetics regulations in the EuropeanUnion, ingredients
(including those in the form ofnanoparticles) can be used for most
purposes withoutprior approval, provided they are not on the list
ofbanned or restricted use chemicals and thatmanufacturers declare
the final product to be safe.Given our concerns about the toxicity
of anynanoparticles penetrating the skin we recommend thattheir use
in products be dependent on a favourableopinion by the relevant
European Commission scientificsafety advisory committee. A
favourable opinion hasbeen given for the nanoparticulate form of
titaniumdioxide (because chemicals used as UV filters must
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undergo an assessment by the advisory committeebefore they can
be used) but insufficient informationhas been provided to allow an
assessment of zinc oxide.In the meantime we recommend that
manufacturerspublish details of the methodologies they have used
inassessing the safety of their products containingnanoparticles
that demonstrate how they have takenaccount that properties of
nanoparticles may bedifferent from larger forms. We do not expect
this toapply to many manufacturers since our understanding isthat
nanoparticles of zinc oxide are not used extensivelyin cosmetics in
Europe. Based on our recommendationthat chemicals produced in the
form of nanoparticlesshould be treated as new chemicals, we believe
that theingredients lists for consumer products should identifythe
fact that manufactured nanoparticles have beenadded. Nanoparticles
may be included in moreconsumer products in the future, and we
recommendthat the European Commission, with the support of theUK,
review the adequacy of the current regulatoryregime with respect to
the introduction of nanoparticlesinto any consumer products.
39 Although we think it unlikely that nanoparticles ornanotubes
will be released from most materials in whichthey have been fixed,
we see any risk of such releasebeing greatest during disposal,
destruction or recycling.We therefore recommend that manufacturers
ofproducts that fall under extended producerresponsibility regimes
such as end-of-life regulationspublish procedures outlining how
these materials will bemanaged to minimise possible human
andenvironmental exposure.
40 Our review of regulation has not been exhaustiveand we
recommend that all relevant regulatory bodiesconsider whether
existing regulations are appropriate toprotect humans and the
environment from the hazardswe have identified, publish their
reviews and explainhow they will address any regulatory gaps.
Futureapplications of nanotechnologies may have an impacton other
areas of regulation as, for example,developments in sensor
technology may haveimplications for legislation relating to
privacy. It istherefore important that regulatory bodies
includefuture applications of nanotechnologies in their
horizon-scanning programmes to ensure that any regulatorygaps are
identified at an appropriate stage.
41 Overall, given appropriate regulation and researchalong the
lines just indicated, we see no case for themoratorium which some
have advocated on thelaboratory or commercial production of
manufacturednanomaterials.
Ensuring the responsible development of newand emerging
technologies
42 Nanoscience and nanotechnologies are evolvingrapidly, and the
pressures of international competitionwill ensure that this will
continue. The UK GovernmentsChief Scientific Adviser should
therefore commission anindependent group in two years time, and
again in fiveyears time, to review what action has been taken as
aresult of our recommendations, to assess hownanoscience and
nanotechnologies have developed inthe interim, and to consider the
ethical, social, health,environmental, safety and regulatory
implications ofthese developments. This group should
includerepresentatives of, and consult with, the
relevantstakeholder groups.
43 More generally, this study has highlighted again thevalue of
identifying as early as possible new areas ofscience and technology
that have the potential toimpact strongly on society. The Chief
Scientific Advisershould therefore establish a group that brings
togetherrepresentatives of a wide range of stakeholders to
meetbi-annually to review new and emerging technologies,to identify
at the earliest possible stage areas whereissues needing Government
attention may arise, and toadvise on how these might be addressed.
The work ofthis group should be made public and all
stakeholdersshould be encouraged to engage with the emergingissues.
We expect this group to draw upon the work ofthe other bodies
across Government with horizon-scanning roles rather than to
duplicate their work.
44 We look forward to the response to this reportfrom the UK
Government and from the other parties atwhom the recommendations
are targeted. This studyhas generated a great deal of interest
among a widerange of stakeholders, both within the UK
andinternationally. As far as we are aware it is the first studyof
its kind, and we expect its findings to contribute tothe
responsible development of nanoscience andnanotechnology
globally.
-
1.1 Hopes and concerns about nanoscienceand nanotechnologies
1 Nanoscience and nanotechnologies are widely seenas having huge
potential to bring benefits in areas asdiverse as drug development,
water decontamination,information and communication technologies,
and theproduction of stronger, lighter materials. They
areattracting rapidly increasing investments fromgovernments and
from businesses in many parts of theworld; it has been estimated
that total global investmentin nanotechnologies is currently around
5 billion, 2 billion of which comes from private sources(European
Commission 2004a) (see also Table 1.1). The number of published
patents in nanotechnologyincreased fourfold from 1995 (531 parents)
to 2001(1976 patents) (3i 2002). Although it is too early toproduce
reliable figures for the global market, onewidely quoted estimate
puts the annual value for allnanotechnologies-related products
(includinginformation and communication technologies) at $1
trillion by 20112015 (NSF 2001). Although manypeople believe that
nanotechnologies will have animpact across a wide range of sectors,
a survey ofexperts in nanotechnologies across the world
identifiedhype (misguided promises that nanotechnology can
fixeverything) as the factor most likely to result in abacklash
against it (3i 2002).
2 Against this background of increased researchfunding and
interest from industry, several non-governmental organizations
(NGOs) and somenanotechnologists have expressed concerns
aboutcurrent and potential future developments ofnanotechnology.
These include uncertainties about theimpact of new nanomaterials on
human health,
questions about the type of applications that could arisefrom
the expected convergence, in the longer term, ofnanotechnologies
with technologies such asbiotechnology, information technology (IT)
and artificialintelligence, and suggestions that future
developmentsmight bring self-replicating nano-robots that
mightdevastate the world (Joy 2000; ETC 2003a). Others
havequestioned the adequacy of current regulatoryframeworks to deal
with these new developments, andwhether applications will benefit
or disenfranchisedeveloping countries (Arnall 2003).
3 The media has reflected the hopes and concernsabout
nanoscience and nanotechnology.
4 In January 2003 the Better Regulation Task Force(BRTF)
published its report Scientific Research:Innovation with Controls
(Better Regulation Task Force2003), which included a consideration
ofnanotechnologies. Its first recommendation was that theUK
Government should enable the public, throughdebate, to consider the
risks of nanotechnologies forthemselves. Other recommendations
advocatedopenness in decision making, involving the public in
thedecision-making process, developing two-waycommunication
channels and taking a strong lead overthe handling of any issues of
risk to emerge fromnanotechnologies. In its response to the
firstrecommendation, the Government stated that therewas currently
no obvious focus for an informed debate,but that it was initiating
work that would examinewhether there were any areas of
nanotechnology whichraise or will raise specific safety,
environmental or ethicalissues that would warrant further study
(UKGovernment 2003).
The Royal Society & The Royal Academy of Engineering
Nanoscience and nanotechnologies | July 2004 | 1
1 Introduction
Table 1.1 Examples of public funding for research and
development (R&D) in nanoscience and nanotechnology(source:
European Commission 2004a).
Country Expenditure on nanoscience and nanotechnologies
Europe Current funding for nanotechnology R&D is about 1
billion euros, two-thirds of which comesfrom national and regional
programmes.
Japan Funding rose from $400M in 2001 to $800M in 2003 and is
expected to rise by a further 20%in 2004.
USA The USAs 21st Century Nanotechnology Research and
Development Act (passed in 2003)allocated nearly $3.7 billion to
nanotechnology from 2005 to 2008 (which excludes asubstantial
defence-related expenditure). This compares with $750M in 2003.
UK With the launch of its nanotechnology strategy in 2003, the
UK Government pledged 45Mper year from 2003 to 2009.
-
1.2 Terms of reference and conduct of thestudy
5 In June 2003, following its response to the BRTF,the UK
Government commissioned the Royal Societyand the Royal Academy of
Engineering (the UKsnational academies of science and of
engineering,respectively) to conduct an independent study
onnanotechnology. The terms of reference of our study,jointly
agreed by the Office of Science and Technologyand the two
Academies, were as follows:
define what is meant by nanoscience andnanotechnology;
summarise the current state of scientific knowledgeabout
nanotechnology;
identify the specific applications of the newtechnologies, in
particular where nanotechnology isalready in use;
carry out a forward look to see how the technologymight be used
in future, where possible estimating thelikely time-scales in which
the most far-reachingapplications of the technology might become
reality;
identify what environmental, health and safety, ethicalor
societal implications or uncertainties may arise fromthe use of the
technology, both current and future;
identify areas where regulation needs to be considered.
6 The two academies convened a multidisciplinaryworking group of
experts in science and engineering,medicine, social science,
consumer affairs, ethical issuesand the environment to conduct this
study (see Annex Afor a list of Working Group members). The study
wasconducted independently of Government, which wasnot involved in
the selection of the working groupmembers or its methods of
working, and which did notview the report before it was printed. We
received muchwritten evidence, and we held a series of oral
evidencesessions and workshops with a range of stakeholdersfrom the
UK and overseas. The volume of evidence thatwas sent in for the
Working Group to consider andfollow up extended the time taken to
complete thisproject beyond that originally anticipated. At the
outsetof the study it was agreed that the report should
includepublic concerns and that data should be collected
aboutpublic awareness of nanotechnology, which could formimportant
baseline data. The market research companyBMRB International was
commissioned to researchpublic attitudes to nanotechnology, which
took theform of two workshops and a short market survey.
Theevidence was published as the project progressed andcomments
were invited through a dedicated website(www.nanotec.org.uk). A
detailed description of the
conduct of the study can be found in Annex B. We areextremely
grateful to all those organisations andindividuals who contributed
to the study; they are listedin Annex C. Their contributions can be
found on ourwebsite and are available on the CD at the back of
thehardcopy version of this report. In the report
thesecontributions have been referred to as evidence. Thereport was
peer reviewed by a small group of Fellowsfrom the two academies
(listed in Annex A) beforebeing considered by the two academies. It
has beenendorsed by the Council of the Royal Society andapproved
for publication by the Royal Academy ofEngineering.
1.3 Report overview
7 In Chapter 2 we introduce nanoscience andnanotechnologies, and
explain the definitions of eachthat we used during the study. In
Chapter 3 we giveexamples of key current research, and current
andpotential future advances in: nanomaterials;nanometrology;
electronics, optoelectronics and ICT;and bio-nanotechnology. We
also look at the benefitsthey are currently providing and might
provide in theshort, medium and longer term. In Chapter 4 we look
atcurrent and possible future industrial applications
ofnanotechnology, and examine some of the barriers to itstake-up by
industry. In Chapters 3 and 4 we haveprovided an overview (rather
than a detailedassessment) of current and potential
futuredevelopments in, and applications of, nanoscience
andnanotechnologies, against which health, safety,environmental,
social and ethical implications (addressedlater in the report)
could be considered. The Taylorreport (DTI 2002) reviewed the state
of nanotechnologyapplications in industry in the UK and proposed a
seriesof actions to accelerate and support increased
industrialinvestment in the exploitation of nanotechnology in
theUK. It was not our intention to critique or update theTaylor
report or to identify research priorities fornanoscience and
nanotechnology. The House ofCommons Science and Technology
Committee hasrecently evaluated the implementation of
therecommendations of the Taylor report (House ofCommons
2004a).
8 In Chapter 5 we evaluate the potential health, safetyand
environmental implications of nanotechnologies,and in Chapter 6 we
consider the potential social andethical implications. In both
chapters we identify themain gaps in knowledge related to the
potential impactsof nanotechnologies. Chapter 7 outlines the
results ofour commissioned research into public attitudes
tonanotechnology in Great Britain, and considers the roleof
multi-stakeholder dialogue in the future developmentof
nanotechnologies. The implications of ourconclusions for the
current regulatory framework are
The Royal Society & The Royal Academy of Engineering2 | July
2004 | Nanoscience and nanotechnologies
-
outlined in Chapter 8. Finally, Chapters 9 and 10contain our
overall conclusions and list ourrecommendations.
1.4 Next steps
9 We look forward to the response to this reportfrom the UK
Government and from the other parties atwhom the recommendations
are targeted. This studyhas generated a great deal of interest
among a widerange of stakeholders, both within the UK and
internationally. As far as we are aware it is the first studyof
its kind, and we expect its findings to contribute tothe
responsible development of nanoscience andnanotechnology globally.
The two academies willcontinue to participate in this important
area. The issuesraised and conclusions reached in this report can
bedebated through the discussion section of the dedicatedwebsite
(www.nanotec.org.uk). We will hold an openmeeting in London to
discuss the reports findingsshortly after its publication.
The Royal Society & The Royal Academy of Engineering
Nanoscience and nanotechnologies | July 2004 | 3
-
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1 The first term of reference of this study was to definewhat is
meant by nanoscience and nanotechnology.However, as the term
nanotechnology encompassessuch a wide range of tools, techniques
and potentialapplications, we have found it more appropriate to
referto nanotechnologies. Our definitions were developedthrough
consultation at our workshop meeting withscientists and engineers
and through commentsreceived through the study website.
2 Although there is no sharp distinction betweenthem, in this
report we differentiate betweennanoscience and nanotechnologies as
follows.
3 The prefix nano is derived from the Greek wordfor dwarf. One
nanometre (nm) is equal to one-billionthof a metre, 109m. A human
hair is approximately80,000nm wide, and a red blood cell
approximately 7000nm wide. Figure 2.1 shows the nanometre
incontext. Atoms are below a nanometre in size, whereasmany
molecules, including some proteins, range from ananometre
upwards.
4 The conceptual underpinnings of nanotechnologieswere first
laid out in 1959 by the physicist RichardFeynman, in his lecture
Theres plenty of room at thebottom (Feynman 1959). Feynman explored
thepossibility of manipulating material at the scale ofindividual
atoms and molecules, imagining the whole ofthe Encyclopaedia
Britannica written on the head of apin and foreseeing the
increasing ability to examine andcontrol matter at the
nanoscale.
5 The term nanotechnology was not used until1974, when Norio
Taniguchi, a researcher at theUniversity of Tokyo, Japan used it to
refer to the abilityto engineer materials precisely at the
nanometre level(Taniguchi 1974). The primary driving force
forminiaturisation at that time came from the electronicsindustry,
which aimed to develop tools to create smaller(and therefore faster
and more complex) electronicdevices on silicon chips. Indeed, at
IBM in the USA a
technique called electron beam lithography was used tocreate
nanostructures and devices as small as 4070nmin the early
1970s.
6. The size range that holds so much interest istypically from
100nm down to the atomic level(approximately 0.2nm), because it is
in this range(particularly at the lower end) that materials can
havedifferent or enhanced properties compared with thesame
materials at a larger size. The two main reasonsfor this change in
behaviour are an increased relativesurface area, and the dominance
of quantum effects.An increase in surface area (per unit mass) will
result ina corresponding increase in chemical reactivity,
makingsome nanomaterials useful as catalysts to improve
theefficiency of fuel cells and batteries. As the size ofmatter is
reduced to tens of nanometres or less,quantum effects can begin to
play a role, and these cansignificantly change a materials optical,
magnetic orelectrical properties. In some cases,
size-dependentproperties have been exploited for centuries.
Forexample, gold and silver nanoparticles (particles ofdiameter
less than 100 nm; see section 3.2) have beenused as coloured
pigments in stained glass and ceramicssince the 10th century AD
(Erhardt 2003). Depending ontheir size, gold particles can appear
red, blue or gold incolour. The challenge for the ancient
(al)chemists was tomake all nanoparticles the same size (and hence
thesame colour), and the production of single-sizenanoparticles is
still a challenge today.
7. At the larger end of our size range, other effectssuch as
surface tension or stickiness are important,which also affect
physical and chemical properties. Forliquid or gaseous environments
Brownian motion, whichdescribes the random movement of larger
particles ormolecules owing to their bombardment by
smallermolecules and atoms, is also important. This effectmakes
control of individual atoms or molecules in theseenvironments
extremely difficult.
8. Nanoscience is concerned with understandingthese effects and
their influence on the properties ofmaterial. Nanotechnologies aim
to exploit these effectsto create structures, devices and systems
with novelproperties and functions due to their size.
9. In some senses, nanoscience and nanotechnologiesare not new.
Many chemicals and chemical processeshave nanoscale features for
example, chemists havebeen making polymers, large molecules made up
of tinynanoscalar subunits, for many decades.Nanotechnologies have
been used to create the tinyfeatures on computer chips for the past
20 years. Thenatural world also contains many examples of
nanoscalestructures, from milk (a nanoscale colloid)
tosophisticated nanosized and nanostructured proteins
Box 2.1 Definitions of nanoscience and nanotechnologies
Nanoscience is the study of phenomena andmanipulation of
materials at atomic, molecular andmacromolecular scales, where
properties differsignificantly from those at a larger scale.
Nanotechnologies are the design, characterisation,production and
application of structures, devices andsystems by controlling shape
and size at nanometrescale.
The Royal Society & The Royal Academy of Engineering
Nanoscience and nanotechnologies | July 2004 | 5
2 What are nanoscience and nanotechnologies?
-
that control a range of biological activities, such asflexing
muscles, releasing energy and repairing cells.Nanoparticles occur
naturally, and have been created forthousands of years as the
products of combustion andfood cooking.
10 However, it is only in recent years that sophisticatedtools
have been developed to investigate andmanipulate matter at the
nanoscale, which have greatlyaffected our understanding of the
nanoscale world. Amajor step in this direction was the invention of
thescanning tunnelling microscope (STM) in 1982, and theatomic
force microscope (AFM) in 1986. These tools usenanoscale probes to
image a surface with atomicresolution, and are also capable of
picking up, sliding ordragging atoms or molecules around on
surfaces tobuild rudimentary nanostructures. These tools arefurther
described in Box 3.1. In a now famousexperiment in 1990, Don Eigler
and Erhard Schweizer atIBM moved xenon atoms around on a nickel
surface towrite the company logo (Eigler and Schweizer 1990)(see
Figure 2.1), a laborious process which took a wholeday under
well-controlled conditions. The use of thesetools is not restricted
to engineering, but has beenadopted across a range of disciplines.
AFM, for example,is routinely used to study biological molecules
such asproteins.
11 The technique used by Eigler and Schweizer is onlyone in the
range of ways used to manipulate andproduce nanomaterials, commonly
categorised as eithertop-down or bottom-up. Top-down
techniquesinvolve starting with a block of material, and etching
ormilling it down to the desired shape, whereas bottom-
up involves the assembly of smaller sub-units (atoms
ormolecules) to make a larger structure. The mainchallenge for
top-down manufacture is the creation ofincreasingly small
structures with sufficient accuracy,whereas for bottom-up
manufacture, it is to makestructures large enough, and of
sufficient quality, to beof use as materials. These two methods
have evolvedseparately and have now reached the point where thebest
achievable feature size for each technique isapproximately the
same, leading to novel hybrid ways ofmanufacture.
12 Nanotechnologies can be regarded as
genuinelyinterdisciplinary, and have prompted the
collaborationbetween researchers in previously disparate areas
toshare knowledge, tools and techniques. Anunderstanding of the
physics and chemistry of matterand processes at the nanoscale is
relevant to all scientificdisciplines, from chemistry and physics
to biology,engineering and medicine. Indeed, it could be arguedthat
evolutionary developments in each of these fieldstowards
investigating matter at increasingly small sizescales has now come
to be known as nanotechnology.
13 It will be seen in Chapters 3 and 4 that nanoscienceand
nanotechnologies encompass a broad and variedrange of materials,
tools and approaches. Apart from acharacteristic size scale, it is
difficult to findcommonalities between them. We should not
thereforeexpect them to have the same the same
health,environmental, safety, social or ethical implications
orrequire the same approach to regulation; these issuesare dealt
with in Chapters 5 8.
The Royal Society & The Royal Academy of Engineering6 | July
2004 | Nanoscience and nanotechnologies
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3 Science and applications
3.1 Introduction
1 In this chapter we provide an overview of some keycurrent
developments in nanoscience andnanotechnologies, and highlight some
possible futureapplications. The chapter is informed by evidence
fromscientists and engineers in academia and industry.
Itillustrates the wide-ranging interest in these areas andprovides
a background to the later chapters, whichaddress health,
environmental, social, ethical andregulatory implications of
nanotechnologies. It does notconsider in detail the developments in
nanoscience andnanotechnologies in all scientific and engineering
fields.
2 As nanoscience and nanotechnologies cover such awide range of
fields (from chemistry, physics andbiology, to medicine,
engineering and electronics), wehave considered them in four broad
categories:nanomaterials; nanometrology;
electronics,optoelectronics and information and
communicationtechnology; and bio-nanotechnology andnanomedicine.
This division helps to distinguishbetween developments in different
fields, but there isnaturally some overlap.
3 Where possible, we define the development offuture
applications as short term (under 5years),medium term (515 years),
and long term (over20years). It may be that some of the
potentialapplications that we identify are never realised,
whereasothers that are currently unforeseen could have a
majorimpact. We also identify potential in environmental,health and
safety, ethical or societal implications oruncertainties that are
discussed further in later chapters.
4 Current industrial applications of nanotechnologiesare dealt
with in Chapter 4, as are the factors that willinfluence their
application in the future.
3.2 Nanomaterials
3.2.1 Introduction to nanomaterials
5 A key driver in the development of new andimproved materials,
from the steels of the 19th centuryto the advanced materials of
today, has been the abilityto control their structure at smaller
and smaller scales.The overall properties of materials as diverse
as paintsand silicon chips are determined by their structure at
themicro- and nanoscales. As our understanding ofmaterials at the
nanoscale and our ability to controltheir structure improves, there
will be great potential tocreate a range of materials with novel
characteristics,functions and applications.
6 Although a broad definition, we categorisenanomaterials as
those which have structuredcomponents with at least one dimension
less than100nm. Materials that have one dimension in thenanoscale
(and are extended in the other two dimensions)are layers, such as a
thin films or surface coatings. Someof the features on computer
chips come in this category.Materials that are nanoscale in two
dimensions (andextended in one dimension) include nanowires
andnanotubes. Materials that are nanoscale in threedimensions are
particles, for example precipitates, colloidsand quantum dots (tiny
particles of semiconductormaterials). Nanocrystalline materials,
made up ofnanometre-sized grains, also fall into this category.
Someof these materials have been available for some time;others are
genuinely new. The aim of this chapter is togive an overview of the
properties, and the significantforeseeable applications of some key
nanomaterials.
7 Two principal factors cause the properties ofnanomaterials to
differ significantly from othermaterials: increased relative
surface area, and quantumeffects. These factors can change or
enhance propertiessuch as reactivity, strength and electrical
characteristics.As a particle decreases in size, a greater
proportion ofatoms are found at the surface compared to
thoseinside. For example, a particle of size 30 nm has 5% ofits
atoms on its surface, at 10 nm 20% of its atoms, andat 3 nm 50% of
its atoms. Thus nanoparticles have amuch greater surface area per
unit mass compared withlarger particles. As growth and catalytic
chemicalreactions occur at surfaces, this means that a given massof
material in nanoparticulate form will be much morereactive than the
same mass of material made up oflarger particles.
8 In tandem with surface-area effects, quantumeffects can begin
to dominate the properties of matteras size is reduced to the
nanoscale. These can affect theoptical, electrical and magnetic
behaviour of materials,particularly as the structure or particle
size approachesthe smaller end of the nanoscale. Materials that
exploitthese effects include quantum dots, and quantum welllasers
for optoelectronics.
9 For other materials such as crystalline solids, as thesize of
their structural components decreases, there ismuch greater
interface area within the material; this cangreatly affect both
mechanical and electrical properties.For example, most metals are
made up of smallcrystalline grains; the boundaries between the
grainslow down or arrest the propagation of defects whenthe
material is stressed, thus giving it strength. If thesegrains can
be made very small, or even nanoscale insize, the interface area
within the material greatly
The Royal Society & The Royal Academy of Engineering
Nanoscience and nanotechnologies | July 2004 | 7
-
increases, which enhances its strength. For
example,nanocrystalline nickel is as strong as hardened
steel.Understanding surfaces and interfaces is a key challengefor
those working on nanomaterials, and one wherenew imaging and
analysis instruments are vital.
10 Nanomaterials are not simply another step in
theminiaturization of materials. They often require verydifferent
production approaches. As introduced inChapter 2, and discussed
further in Chapter 4, there areseveral processes to create
nanomaterials, classified astop-down and bottom-up. Although
manynanomaterials are currently at the laboratory stage
ofmanufacture, a few of them are being commercialised.
3.2.2 Nanoscience in this area
11 Below we outline some examples of nanomaterialsand the range
of nanoscience that is aimed atunderstanding their properties. As
will be seen, thebehaviour of some nanomaterials is well
understood,whereas others present greater challenges.
a) Nanoscale in one dimension
Thin films, layers and surfaces12 One-dimensional nanomaterials,
such as thin filmsand engineered surfaces, have been developed
andused for decades in fields such as electronic devicemanufacture,
chemistry and engineering. In the siliconintegrated-circuit
industry, for example, many devicesrely on thin films for their
operation, and control of filmthicknesses approaching the atomic
level is routine.Monolayers (layers that are one atom or molecule
deep)are also routinely made and used in chemistry. Theformation
and properties of these layers are reasonablywell understood from
the atomic level upwards, even inquite complex layers (such as
lubricants). Advances arebeing made in the control of the
composition andsmoothness of surfaces, and the growth of films.
13 Engineered surfaces with tailored properties such aslarge
surface area or specific reactivity are used routinelyin a range of
applications such as in fuel cells andcatalysts (see section
3.2.3b). The large surface areaprovided by nanoparticles, together
with their ability toself assemble on a support surface, could be
of use in allof these applications.
14 Although they represent incremental developments,surfaces
with enhanced properties should find applicationsthroughout the
chemicals and energy sectors. Thebenefits could surpass the obvious
economic andresource savings achieved by higher activity and
greaterselectivity in reactors and separation processes, toenabling
small-scale distributed processing (makingchemicals as close as
possible to the point of use). Thereis already a move in the
chemical industry towards this.Another use could be the
small-scale, on-site productionof high value chemicals such as
pharmaceuticals.
b) Nanoscale in two dimensions
15 Two dimensional nanomaterials such as tubes andwires have
generated considerable interest among thescientific community in
recent years. In particular, theirnovel electrical and mechanical
properties are thesubject of intense research.
Carbon nanotubes16 Carbon nanotubes (CNTs) were first observed
bySumio Iijima in 1991 (Iijima 1991). CNTs are extendedtubes of
rolled graphene sheets. There are two types ofCNT: single-walled
(one tube) or multi-walled (severalconcentric tubes) (Figure 3.1).
Both of these are typicallya few nanometres in diameter and several
micrometres (10-6m) to centimetres long. CNTs have assumed
animportant role in the context of nanomaterials, becauseof their
novel chemical and physical properties. They aremechanically very
strong (their Youngs modulus is over1 terapascal, making CNTs as
stiff as diamond), flexible(about their axis), and can conduct
electricity extremelywell (the helicity of the graphene sheet
determineswhether the CNT is a semiconductor or metallic). All
ofthese remarkable properties give CNTs a range ofpotential
applications: for example, in reinforcedcomposites, sensors,
nanoelectronics and displaydevices.
Figure 3.1a Schematic of a single-walled carbon nanotube
(SWNT)
Figure 3.1b Schematic of a multi-walled carbon nanotube
(MWNT)
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17 CNTs are now available commercially in limitedquantities.
They can be grown by several techniques,which are discussed in
section 4.3.1b. However, theselective and uniform production of
CNTs with specificdimensions and physical properties is yet to be
achieved.The potential similarity in size and shape between CNTsand
asbestos fibres has led to concerns about their safety,which we
address in detail in sections 5.3.1b and 5.3.2a.
Inorganic nanotubes18 Inorganic nanotubes and inorganic
fullerene-likematerials based on layered compounds such
asmolybdenum disulphide were discovered shortly afterCNTs. They
have excellent tribological (lubricating)properties, resistance to
shockwave impact, catalyticreactivity, and high capacity for
hydrogen and lithiumstorage, which suggest a range of
promisingapplications. Oxide-based nanotubes (such as
titaniumdioxide) are being explored for their applications
incatalysis, photo-catalysis and energy storage.
Nanowires19 Nanowires are ultrafine wires or linear arrays
ofdots, formed by self-assembly. They can be made from awide range
of materials. Semiconductor nanowiresmade of silicon, gallium
nitride and indium phosphidehave demonstrated remarkable optical,
electronic andmagnetic characteristics (for example, silica
nanowirescan bend light around very tight corners). Nanowireshave
potential applications in high-density data storage,either as
magnetic read heads or as patterned storagemedia, and electronic
and opto-electronic nanodevices,for metallic interconnects of
quantum devices andnanodevices. The preparation of these nanowires
relieson sophisticated growth techniques, which include
self-assembly processes, where atoms arrange themselvesnaturally on
stepped surfaces, chemical vapourdeposition (CVD) onto patterned
substrates,electroplating or molecular beam epitaxy (MBE).
Themolecular beams are typically from thermallyevaporated elemental
sources.
Biopolymers20 The variability and site recognition of
biopolymers,such as DNA molecules, offer a wide range
ofopportunities for the self-organization of wirenanostructures
into much more complex patterns. TheDNA backbones may then, for
example, be coated inmetal. They also offer opportunities to link
nano- andbiotechnology in, for example, biocompatible sensorsand
small, simple motors. Such self-assembly of organicbackbone
nanostructures is often controlled by weakinteractions, such as
hydrogen bonds, hydrophobic, orvan der Waals interactions
(generally in aqueousenvironments) and hence requires quite
differentsynthesis strategies to CNTs, for example. Thecombination
of one-dimensional nanostructuresconsisting of biopolymers and
inorganic compoundsopens up a number of scientific and
technologicalopportunities.
c) Nanoscale in three dimensions
Nanoparticles21 Nanoparticles are often defined as particles of
lessthan 100nm in diameter. In line with our definitions
ofnanoscience and nanotechnologies (see Box 2.1), weclassify
nanoparticles to be particles less than 100nm indiameter that
exhibit new or enhanced size-dependentproperties compared with
larger particles of the samematerial. Nanoparticles exist widely in
the natural world:for example as the products of photochemical
andvolcanic activity, and created by plants and algae. Theyhave
also been created for thousands of years asproducts of combustion
and food cooking, and morerecently from vehicle exhausts.
Deliberatelymanufactured nanoparticles, such as metal oxides, areby
comparison in the minority. In this report we willrefer to these as
natural, pollutant and manufacturednanoparticles, respectively.
22 As described in Chapter 2, nanoparticles are ofinterest
because of the new properties (such as chemicalreactivity and
optical behaviour) that they exhibitcompared with larger particles
of the same materials.For example, titanium dioxide and zinc oxide
becometransparent at the nanoscale, however are able toabsorb and
reflect UV light, and have found applicationin sunscreens.
Nanoparticles have a range of potentialapplications: in the
short-term in new cosmetics, textilesand paints; in the longer
term, in methods of targeteddrug delivery where they could be to
used deliver drugsto a specific site in the body. Nanoparticles can
also bearranged into layers on surfaces, providing a largesurface
area and hence enhanced activity, relevant to arange of potential
applications such as catalysts.
23 Manufactured nanoparticles are typically notproducts in their
own right, but generally serve as rawmaterials, ingredients or
additives in existing products.Although their production is
currently low comparedwith other nanomaterials we have given them
aconsiderable amount of attention in this report. This isbecause
they are currently in a small number ofconsumer products such as
cosmetics and theirenhanced or novel properties may have
implications fortheir toxicity. The evidence submitted during the
courseof our study indicates that for most
applications,nanoparticles will be fixed (for example, attached to
asurface or within in a composite) although in othersthey will be
free or suspended in fluid. Whether they arefixed or free will have
a significant affect on theirpotential health, safety and
environmental impacts. Weaddress these issues in detail in Chapter
5.
Fullerenes (carbon 60)24 In the mid-1980s a new class of carbon
material wasdiscovered called carbon 60 (C60) (Kroto et al 1985).
Adiagram of carbon 60 can be found in Figure 2.1. Theseare
spherical molecules about 1nm in diameter,comprising 60 carbon
atoms arranged as 20 hexagons
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and 12 pentagons: the configuration of a football. TheC60
species was named Buckminsterfullerene inrecognition of the
architect Buckminster Fuller, who waswell-known for building
geodesic domes, and the termfullerenes was then given to any closed
carbon cage. In1990, a technique to produce larger quantities of
C60 wasdeveloped by resistively heating graphite rods in a
heliumatmosphere (Krtschmer et al 1990). Several applicationsare
envisaged for fullerenes, such as miniature ballbearings to
lubricate surfaces, drug delivery vehicles andin electronic
circuits.
Dendrimers25 Dendrimers are spherical polymeric molecules,formed
through a nanoscale hierarchical self-assemblyprocess. There are
many types of dendrimer; the smallestis several nanometres in size.
Dendrimers are used inconventional applications such as coatings
and inks, butthey also have a range of interesting properties
whichcould lead to useful applications. For example,dendrimers can
act as nanoscale carrier molecules andas such could be used in drug
delivery. Environmentalclean-up could be assisted by dendrimers as
they cantrap metal ions, which could then be filtered out ofwater
with ultra-filtration techniques.
Quantum dots26 Nanoparticles of semiconductors (quantum
dots)were theorized in the 1970s and initially created in theearly
1980s. If semiconductor particles are made smallenough, quantum
effects come into play, which limitthe energies at which electrons
and holes (the absenceof an electron) can exist in the particles.
As energy isrelated to wavelength (or colour), this means that
theoptical properties of the particle can be finely tuneddepending
on its size. Thus, particles can be made toemit or absorb specific
wavelengths (colours) of light,merely by controlling their size.
Recently, quantum dotshave found applications in composites, solar
cells(Gratzel cells) and fluorescent biological labels (forexample
to trace a biological molecule) which use boththe small particle
size and tuneable energy levels.Recent advances in chemistry have
resulted in thepreparation of monolayer-protected,
high-quality,monodispersed, crystalline quantum dots as small as2nm
in diameter, which can be conveniently treatedand processed as a
typical chemical reagent.
3.2.3 Applications
27 Below we list some key current and potential short-and
long-term applications of nanomaterials. Mostcurrent applications
represent evolutionarydevelopments of existing technologies: for
example, thereduction in size of electronics devices.
a) Current
Sunscreens and cosmetics28 Nanosized titanium dioxide and zinc
oxide are
currently used in some sunscreens, as they absorb andreflect
ultraviolet (UV) rays and yet are transparent tovisible light and
so are more appealing to the consumer.Nanosized iron oxide is
present in some lipsticks as apigment but it is our understanding
that it is not usedby the European cosmetics sector. The use
ofnanoparticles in cosmetics has raised a number ofconcerns about
consumer safety; we evaluate theevidence relating to these concerns
in section 5.3.2b.
Composites29 An important use of nanoparticles and nanotubesis
in composites, materials that combine one or moreseparate
components and which are designed to exhibitoverall the best
properties of each component. Thismulti-functionality applies not
only to mechanicalproperties, but extends to optical, electrical
andmagnetic ones. Currently, carbon fibres and bundles
ofmulti-walled CNTs are used in polymers to control orenhance
conductivity, with applications such as anti-static packaging. The
use of individual CNTs incomposites is a potential long-term
application (seesection 3.2.3c). A particular type of nanocomposite
iswhere nanoparticles act as fillers in a matrix; forexample,
carbon black used as a filler to reinforce cartyres. However,
particles of carbon black can range fromtens to hundreds of
nanometres in size, so not allcarbon black falls within our
definition of nanoparticles.
Clays30 Clays containing naturally occurring nanoparticleshave
long been important as construction materials andare undergoing
continuous improvement. Clay particlebased composites containing
plastics and nano-sizedflakes of clay are also finding applications
such as usein car bumpers.
Coatings and surfaces31 Coatings with thickness controlled at
the nano- oratomic scale have been in routine production for
sometime, for example in MBE or metal oxide CVD foroptoelectonic
devices, or in catalytically active andchemically functionalized
surfaces. Recently developedapplications include the self-cleaning
window, which iscoated in highly activated titanium dioxide,
engineeredto be highly hydrophobic (water repellent) and
anti-bacterial, and coatings based on nanoparticulate oxidesthat
catalytically destroy chemical agents (Royal Society2004a). Wear
and scratch-resistant hard coatings aresignificantly improved by
nanoscale intermediate layers (ormultilayers) between the hard
outer layer and thesubstrate material. The intermediate layers give
goodbonding and graded matching of elastic and thermalproperties,
thus improving adhesion. A range of enhancedtextiles, such as
breathable, waterproof and stain-resistant fabrics, have been
enabled by the improvedcontrol of porosity at the nanoscale and
surfaceroughness in a variety of polymers and inorganics.
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Tougher and harder cutting tools32 Cutting tools made of
nanocrystalline materials,such as tungsten carbide, tantalum
carbide and titaniumcarbide, are more wear and erosion-resistant,
and lastlonger than their conventional (large-grained)counterparts.
They are finding applications in the drillsused to bore holes in
circuit boards.
b) Short-term
Paints33 Incorporating nanoparticles in paints could
improvetheir performance, for example by making them lighterand
giving them different properties. Thinner paintcoatings
(lightweighting), used for example on aircraft,would reduce their
weight, which could be beneficial tothe environment. However, the
whole life cycle of theaircraft needs to be considered before
overall benefitscan be claimed (see section 4.5). It may also be
possibleto substantially reduce solvent content of paints,
withresulting environmental benefits. New types of
fouling-resistant marine paint could be developed and areurgently
needed as alternatives to tributyl tin (TBT), nowthat the
ecological impacts of TBT have beenrecognised. Anti-fouling surface
treatment is alsovaluable in process applications such as heat
exchange,where it could lead to energy savings. If they can
beproduced at sufficiently low cost, fouling-resistantcoatings
could be used in routine duties such as pipingfor domestic and
industrial water systems. It remainsspeculation whether very
effective anti-fouling coatingscould reduce the use of biocides,
including chlorine.Other novel, and more long-term, applications
fornanoparticles might lie in paints that change colour inresponse
to change in temperature or chemicalenvironment, or paints that
have reduced infra-redabsorptivity and so reduce heat loss.
34 Concerns about the health and environmentalimpacts of
nanoparticles (which we address in detail inChapter 5) may require
the need for the durability andabrasion behaviour of
nano-engineered paints andcoatings to be addressed, so that
abrasion products takethe form of coarse or microscopic
agglomerates ratherthan individual nanoparticles.
Remediation35 The potential of nanoparticles to react
withpollutants in soil and groundwater and transform theminto
harmless compounds is being researched. In onepilot study the large
surface area and high surfacereactivity of iron nanoparticles were
exploited totransform chlorinated hydrocarbons (some of which
arebelieved to be carcinogens) into less harmful endproducts in
groundwater (Zhang 2003). It is also hopedthat they could be used
to transform heavy metals suchas lead and mercury from bioavailable
forms intoinsoluble forms. Serious concerns have been raised
overthe uncontrolled release of nanoparticles into theenvironment;
these are discussed in section 5.4.
Fuel Cells36 Engineered surfaces are essential in fuel cells,
wherethe external surface properties and the pore structureaffect
performance. The hydrogen used as the immediatefuel in fuel cells
may be generated from hydrocarbonsby catalytic reforming, usually
in a reactor moduleassociated directly with the fuel cell. The
potential useof nano-engineered membranes to intensify
catalyticprocesses could enable higher-efficiency, small-scale
fuelcells. These could act as distributed sources of
electricalpower. It may eventually be possible to producehydrogen
locally from sources other than hydrocarbons,which are the
feedstocks of current attention.
Displays37 The huge market for large area, high
brightness,flat-panel displays, as used in television screens
andcomputer monitors, is driving the development of
somenanomaterials. Nanocrystalline zinc selenide, zincsulphide,
cadmium sulphide and lead telluridesynthesized by solgel techniques
(a process for makingceramic and glass materials, involving the
transitionfrom a liquid sol phase to a solid gel phase)
arecandidates for the next generation of light-emittingphosphors.
CNTs are being investigated for low voltagefield-emission displays;
their strength, sharpness,conductivity and inertness make them
potentially veryefficient and long-lasting emitters.
Batteries38 With the growth in portable electronic
equipment(mobile phones, navigation devices, laptop
computers,remote sensors), there is great demand for
lightweight,high-energy density batteries. Nanocrystalline
materialssynthesized by solgel techniques are candidates
forseparator plates in batteries because of their
foam-like(aerogel) structure, which can hold considerably
moreenergy than conventional ones. Nickelmetal hydridebatteries
made of nanocrystalline nickel and metalhydrides are envisioned to
require less frequentrecharging and to last longer because of their
largegrain boundary (surface) area.
Fuel additives39 Research is underway into the addition
ofnanoparticulate ceria (cerium oxide) to diesel fuel toimprove
fuel economy by reducing the degradation offuel consumption over
time (Oxonica 2003).
Catalysts40 In general, nanoparticles have a high surface
area,and hence provide higher catalytic activity.Nanotechnologies
are enabling changes in the degree ofcontrol in the production of
nanoparticles, and thesupport structure on which they reside. It is
possible tosynthesise metal nanoparticles in solution in
thepresence of a surfactant to form highly orderedmonodisperse
films of the catalyst nanoparticles on asurface. This allows more
uniformity in the size andchemical structure of the catalyst, which
in turn leads to
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greater catalytic activity and the production of fewer
by-products. It may also be possible to engineer specific
orselective activity. These more active and durablecatalysts could
find early application in cleaning upwaste streams. This will be
particularly beneficial if itreduces the demand for platinum-group
metals, whoseuse in standard catalytic units is starting to emerge
as aproblem, given the limited availability of these metals.
c) Longer-term applications
Carbon nanotube composites41 CNTs have exceptional mechanical
properties,particularly high tensile strength and light weight.
Anobvious area of application would be in nanotube-reinforced
composites, with performance beyondcurrent carbon-fibre composites.
One current limit tothe introduction of CNTs in composites is the
problem ofstructuring the tangle of nanotubes in a
well-orderedmanner so that use can be made of their
strength.Another challenge is generating strong bondingbetween CNTs
and the matrix, to give good overallcomposite performance and
retention during wear orerosion of composites. The surfaces of CNTs
are smoothand relatively unreactive, and so tend to slip through
thematrix when it is stressed. One approach that is beingexplored
to prevent this slippage is the attachment ofchemical side-groups
to CNTs, effectively to formanchors. Another limiting factor is the
cost ofproduction of CNTs. However, the potential benefits ofsuch
light, high strength material in numerousapplications for
transportation are such that significantfurther research is
likely.
Lubricants42 Nanospheres of inorganic materials could be usedas
lubricants, in essence by acting as nanosized ballbearings. The
controlled shape is claimed to make themmore durable than
conventional solid lubricants andwear additives. Whether the
increased financial andresource cost of producing them is offset by
the longerservice life of lubricants and parts remains to
beinvestigated (along the lines of the methodologyoutlined in
section 4.5). It is also claimed that thesenanoparticles reduce
friction between metal surfaces,particularly at high normal loads.
If so, they should findtheir first applications in high-performance
engines anddrivers; this could include the energy sector as well
astransport. There is a further claim that this type oflubricant is
effective even if the metal surfaces are nothighly smooth. Again,
the benefits of reduced cost andresource input for machining must
be compared againstproduction of nanolubricants. In all these
applications,the particles would be dispersed in a conventional
liquidlubricant; design of the lubricant system must
thereforeinclude measures to contain and manage waste.
Magnetic materials43 It has been shown that magnets made
ofnanocrystalline yttriumsamariumcobalt grains possess
unusual magnetic properties due to their extremelylarge grain
interface area (high coercivity can beobtained because
magnetization flips cannot easilypropagate past the grain
boundaries). This could lead toapplications in motors, analytical
instruments likemagnetic resonance imaging (MRI), used widely
inhospital