Part 5 of a series on rethinking science and technology for the 21st century

Last time in this series of occasional blogs, I made the rather bold statement that while science and technology are going to have a highly visible impact on our lives over the next few decades, progress is going to be underpinned in most cases by our increasing control over materials at the invisible nanoscale. It isn’t exactly intuitive why this should be the case though—how on earth can engineering matter on a scale a billion time smaller than the average person be so important?

In trying to answer this question, I want to take a rather unconventional approach and explore three advantages of working at this scale: Smallness, strangeness and sophistication.

Smallness. Size matters—it’s something we all understand intuitively.  There are occasions when you can do something with a small object or device that would be impossible otherwise.  This photo from Ilan Kelman for instance illustrates the idea perfectly: There are times that “smallness” gets you to places that larger objects can’t reach—like parking spaces!

It’s easy to see how making things that we can see and touch small can enhance their value.  But the utility of smallness doesn’t stop when things become invisible to the naked eye.  All the way down to the nanometer scale, there are opportunities to make things work better or work differently by making them small.

Here’s a very trivial example of smallness making a difference at the nanometer scale, but it’s a useful illustration of why size matters:

Silver is a great antimicrobial agent.  It’s been used for millennia to prevent infections from spreading and is one of the reasons why “silverware” is—or used to be—made of the metal.

But it’s not that easy to use.  Large lumps of metal aren’t always that easy to incorporate into products that you want to keep sterile or have antimicrobial properties.

One solution is convert the individual silver atoms into charged ions that can be dissolved in liquids and incorporated into other substances.  As its the ionic form of silver that is most harmful to microbes, this makes a lot of sense.  But ionic silver isn’t that easy to use either.  Say you have a silk scarf or a wound dressing you want to imbue with antimicrobial properties.  Getting those silver ions in there without changing the physical feel and nature of the material is a tough challenge.

This is where smallness comes in.  Make the silver metal into nanometer-sized particles, and it becomes relatively easy to get it into a wide range of products.  Because these are particles we are dealing with, there isn’t so much complex chemistry behind using them.  And because they are so small, they don’t unduly affect the feel and performance of the products they are used in.  As an added advantage, replacing a few large particles with millions of small ones increases the chances of microbes coming into contact with them manyfold.

Because of the advantages of smallness when it comes to using silver as an antimicrobial, there has been an explosion of products using silver nanoparticles—everything from refrigerators to socks to toothpaste.  And all because smallness gets you to new places.

It’s a trivial example, but it does illustrate an important way in which “smallness” through increased control over matter at the nanoscale leads to added value.

It’s not the only way though—there is also strangeness.

Strangeness. No two questions about it, things can get a little weird down at the nanoscale. This is good – it means that controlling matter at this scale opens up a whole new toolbox of material properties that can be put to good use.

Vicki Colvin at Rice University came up with a great analogy for strangeness a few years back.  It went something like this:  Imagine you have a cat.  It looks like a cat, sounds like a cat, smells like a cat.  Now, imagine you have a technology that allows you to make that cat smaller.  As you shrink your cat down, it gets smaller and smaller, but still retains its essential cat-ness.  But imagine reaching a point where suddenly, instead of looking, smelling, sounding like a cat, your cat becomes a dog!

This is the very essence of strangeness—materials behaving in unexpected and sometimes radically different ways when they are engineered at a nanometer scale.  This doesn’t always happen—it depends on the material and the scale on which the material is being engineered—but in some cases the changes in behavior can be startling.

A good example is found in the metal gold.

Gold is an inert, yellowish metal—everyone knows this.  It’s lack of reactivity is why so much jewelry is made from the stuff (it doesn’t tarnish), and in part why it holds its value.  But form gold into particles just a new nanometers across, and everything changes—the metal does the equivalent of transforming from a cat into a dog.  Instead of appearing yellowish in color, the particles now appear red, and become highly chemically active.

This change in color has been exploited for millennia in glass-making (unbeknownst to the glass-makers, who had no idea they were making and using nanoparticles), with perhaps the most famous example being the Lycurgus cup from Roman times.  Illuminated from behind, the gold nanoparticle-containing dichroic glass that the cup is made from appears deep red in color.

This strange behavior has a lot to do with how the movement of electrons in materials is affected when they are engineered at a nanometer scale.  As these movements affect everything from electrical conductivity and interactions with electromagnetic radiation—including visible light—to how a material conducts heat, nanometer-scale engineering allows scientists and engineers to tap into material properties that are rarely accessible without control at this level.

But it’s not enough to have a smorgasbord of strangeness at out fingertips—we also need the ability to use these unusual properties.  And this is where sophistication comes in.

Sophistication. As humans, we are pre-programmed to build things.  As kids, we start early—usually with large blocks.  But we soon learn that there are limits to what can be made with these rather awkward building blocks, and so we progress on to finer blocks—think of it as graduating from wooden blocks to Duplo.  However, it isn’t long before we outgrow these bricks and crave something smaller with which to create increasingly sophisticated structures.  And so we discover that ultimate building medium—Lego.

It’s a rather tongue in cheek analogy, but it illustrates something we all know: The smaller the building blocks we use, the more sophisticated the products we can make.  This applies at the human scale, but it just as equally applies at the nanometer scale.  In fact, being able to build with nanometer-scale clumps of atoms and molecules gives us perhaps what is the ultimate construction set.  And before anyone interjects with “surely that’s just chemistry,” the distinction here is the ability to put these small clumps where we want them with nanometer scale precision.  This is sophistication at the nanometer scale, and opens up new possibilities in engineering materials and products with enhanced or unique properties.

It’s probably fair to say that we are just beginning to scratch the surface of what can be achieved through sophisticated nanometer-scale engineering, but already there are examples that hint at the potential that is opening up.

Here you see a schematic of an actual nanometer-scale particle developed by Raoul Kopelman and Martin Philbert at the University of Michigan.  What is particularly interesting is the sophisticated way this particle has been engineered at the nanoscale to carry out a number of tasks.

The core particle is coated with a thin layer of PolyEthylene Glycol (PEG) to make it invisible to the body’s defense systems.  It is also covered with molecules that enable it to attach to a specific target cell—a particular cancer cell in this case.  Internally, the nanoparticle has been engineered with a contrast-enhancing agent, meaning that when sufficient particles are attached to the tumor being treated, they can be seen using imaging techniques like MRI.

Then the really clever bit—the particles have been engineered with a sensitizer.  In essence, this is a component that causes the particle to do something when it receives a signal.  In this case, when the particle is illuminated with a particular wavelength of light, it releases chemicals to kill the cancer cell it is attached to.

This “smart” particle represents an incredible degree of sophistication at the nanometer scale, and does what it does—destroys cancer cells without affecting healthy cells—because of this sophistication.  And it’s only one example from an increasing number of applications that demonstrate what can be achieved when we have the sophistication to build things at close to the scale of individual atoms and molecules.

At the end of the day, smallness, strangeness and sophistication don’t tell you everything you need to know to understand why an increasing ability to control matter at the nanoscale is so important.  But they do provide a pretty good insight—dare I say, a sophisticated insight—into what can be achieved by working at this scale.

They also create a bridge between two largely separate spheres that is poised to take our control over the world in which we live to an entirely new level.  But more of that next time.

Notes

Rethinking science and technology for the 21st century is a series of blogs drawing on a recent lecture given at the James Martin School in Oxford.  This is a bit of an experiment—the serialization of a lecture, and a prelude to a more formal academic paper.  But hopefully it will be both interesting and useful.  I’ll be posting a “rethinking science and technology” blog every week or so, interspersed with the usual eclectic mix of stuff you’ve come to expect from 2020science.

Previously: Control: Gaining mastery over the world at the finest level

Next: Nanoscale control: Leveraging biology

Ten years ago to the month, one of the first research reports detailing the challenges of ensuring the safe use of engineered nanomaterials was delivered to the UK Health and Safety Executive.  The report wasn’t for general release, and you’ll be hard pressed to find a copy of it in the public domain.  But as a co-author, I have a copy skulking around in my archives.  And given it’s ten year anniversary, I’ve been browsing through it, to find out how much has progressed—or not, as the case may be!

The report focused on ultrafine aerosols, and the Health and Safety Laboratory’s ability to respond to then-current, and future, research needs.  As such it was pretty wide ranging, and focused extensively on exposure to incidental nanoscale aerosols—such as welding fume and engine emissions—in the workplace.  But it did encompass the then-nascent field of nanotechnology and “nanophase material synthesis.”  And some of these early assessments of the field bear revisiting.

For anyone interested in what was being written about the potential health and safety issues raised by engineered nanomaterials ten years ago, I’ve extracted a few sections of the report below—for the full thing, you’ll have to go to the UK Health and Safety Executive.

My apologies that the post is so long—I’m only expecting a dedicated few to plough through it.  But at the least, you might want to skip to the end to see how the research recommendations of 1999 compare to those of today—you might be surprised!

A scoping study into ultrafine aerosol research and HSL’s ability to respond to current and future research needs.
IR/A/99/03

Kenny, Maynard et al. 1999

The introduction to the report starts:

Over the past few years a number of epidemiological studies have indicated a tentative link between ambient particulate concentrations, and morbidity and mortality rates (e.g. Dochery et al. 1993, Pope 1996, Schwartz et al. 1993, Schwartz et al. 1991).  In all studies, particles with an aerodynamic diameter less than 10 µm (the PM10 fraction) have been implicated as the key agents.  The lack of an apparent association between particles of specific composition and health effects has indicated the observed effects to be due to some physical aspect of the inhaled particles.  A further link between particle size and health has been indicated by Dochery et al. (1993) who showed a more positive correlation between ill health and particles smaller than 2.5 µm than was seen than with the PM10 fraction.  The possibility of correlations between particle size and number concentration and toxicity has been demonstrated by Oberdörster et al. (1995) by exposing rats to PTFE particles ~20 nm in diameter.  At concentrations of 106 particles cm-3 (corresponding to an equivalent mass concentration of approximately 60 µg m-3) rats exposed for 30 minutes died within 4 hours. At lower concentrations a steep dose response curve was observed between pulmonary inflammatory responses and particle number.  More recent research has begun to indicate a possible material-independent link between inhaled particle surface area and selected toxicological endpoints (e.g. Lison et al. 1997). The possibility of a relationship between fine inhaled particles and ill health is now readily accepted,  although research is still at a very early stage and most published data to date are open to a wide range of interpretations.  Tentative hypotheses concerning possible mechanisms leading to toxicity have been proposed (e.g. Schlesinger 1995, Seyton et al. 1995, Donaldson and McNee 1998), and the impact of inhaling ultrafine particles on both the respiratory and cardiovascular systems have been speculated on.  The US EPA have already acted, partially as a response to earlier epidemiological studies, and introduced the PM2.5 sampling standard for environmental particulates.  Whether the UK is to follow this lead is still under discussion.  However, despite these steps, research so far has raised more questions than answers.  There is debate over the interpretation of the epidemiological studies, and the appropriateness of chosen endpoints in toxicology tests.  Contradictory experimental results are beginning to be published regarding ultrafine particle impact on health (e.g. Pekkanen et al. 1997).  There also appear to be widely conflicting views on what constitutes an ultrafine particle, with implicit cut-off points ranging from 10 µm down to a few nm!

In amongst all the current confusion is the question of whether the alleged health implications of inhaling ultrafine aerosols are of relevance to the workplace.  Much has been made of the apparent health problems amongst vulnerable sectors of the general population following environmental exposures, and the argument is followed through to the conclusion that within a healthy workforce similar problems are unlikely to be seen (backed up by a lack of evidence of severe health problems that are clearly linked to ultrafine aerosols).  However, in part the current uncertainty over the toxicity of ultrafine particles is due to the very limited information available on the nature of so-called ultrafine particles.  Inhaled particles associated with health in epidemiology studies have been very poorly defined, and even the particles used in most well controlled in vitro and in vivo experiments have been poorly characterised.  Without basic information on particle size, morphology, composition and structure, it is clearly not feasible to make value judgements on the nature of inhaled particles, either in the general environment or in the workplace. In the light of the scarcity of information on particle characteristics, the Committee on the Medical Aspects of Air Pollutants has recommended the monitoring of such parameters at a number of environmental locations (COMEAP 1996).  Similar measurements will be essential within the workplace before further speculations on the importance of ultrafine aerosols are made.

In reading this, it is important to remember that the state of the science is ten years on from when this was written—there are now a wealth of publications on the potentially health-relevant behavior of nanometer-scale particles.  Yet the framework of questions set out largely remains as relevant now as it did then.

Perhaps more interestingly, in 1999 the discussion was focused on understanding and managing the health impacts of inhaled particles, NOT whether those particles could be classified as arising from nanotechnology or not.  As a result, the document tends to be more grounded in the science of how fine particles potentially impact on health, rather than how the poorly defined field of “nanotechnology” might lead to health effects.

The report goes on to consider the generation of ultrafine aerosols in the workplace:

In general, very little is known about any aspect of ultrafine aerosols in the workplace.  There are a number of processes such as welding and soldering where intuitively one would expect large numbers of sub-µm particles.  However even in these areas, detailed measurements of particle size do not appear to have been made.  There is a general feeling that in situations where large concentrations of particles are generated, agglomeration will remove ultrafine particles from the aerosol before it is inhaled, thus removing the need to consider ultrafines. However this has not been verified, and evidence exists for significant mass concentrations of ultrafines existing close to generation sources.  Interestingly, researchers are currently speculating that agglomerates with ultrafine primary particles may have the equivalent impact on the lungs as the individual primary particles.  More is known about the products of internal combustion engines, although mainly from the view point of monitoring and reducing environmental emissions.  However very little information on the nature of individual particles in the workplace exists.

Ultrafine aerosols tend to be formed either through nucleation (in particular homogeneous nucleation), gas to particle reactions or through the evaporation of liquid droplets.  The majority of workplace ultrafine particles are likely to arise from the nucleation route, either as combustion products, or within saturated vapours arising from other sources (e.g. welding, smelting, laser ablation).  Evaporation of sub-micron and even micron sized droplets of relatively high purity solvents will result in very small particles.  Where the initial particles are highly charged, there is the possibility of any resulting fine particles exceeding the Rayleigh charge limit and fragmenting into even finer particles.  This is a recognised method of generating ultrafine particles through electrospraying.  To what extent this generation route is present in the workplace is unknown, although it is used for the specific generation of ultrafine particles during nanofabrication.  Gas to particle generation of ultrafine aerosols accounts for the majority of non-combustion particles in the environment, although again the significance of this route within the workplace is unclear.

Following current interest in nanophase technology, and the use of ultrafine particles as precursors in nanophase materials, it is likely that the next few years will see an increase in the industrial generation and use of ultrafine particles.  At present the planned generation of particles tends to be isolated to the production of ultrafine metal oxides such as TiO2, ZnO and fumed silica.  Ultrafine carbon black is also currently generated on a commercial scale. Although the full extent to which ultrafine aerosols are generated as an unwanted by-product within industry is still largely unknown, there are clear cases where the generation rate is high, such as in welding and from internal combustion engines.  Even so, data on the nature of generated aerosols in these areas are sparse.

There follows an assessment of different sources of nanoscale particles in the workplace, from welding to plastic fumes from laser cutting, and a range of other sources.  This is all interesting information, but here I want to focus on the section on ultrafine aerosol precursors in nanophase technology:

Over the last ten years, interest in the unique properties associated with materials having structures on a nanometer scale has been increasing at something approaching an exponential rate.  By restricting ordered atomic arrangements to increasingly small volumes, materials begin to be dominated by the atoms and molecules at the surfaces of these ‘domains’, often leading to properties that are startlingly different from the bulk material.  As the domains become smaller, and hence more dominated by surface atoms and surface energies, so the properties become increasingly unique from either the bulk material or the constituent atoms. So for instance, a relatively inert metal or metal oxide may become a highly effective catalyst when manufactured as ultrafine particles; opaque materials may become transparent when composed of nanoparticles, or vice versa; conductors may become insulators, and insulators conductors; nanophase materials may have many times the strength of the bulk material.  All of these effects and many more have been observed with various materials.  Such material properties that are unique to nanostructured materials that have excited both the scientific and industrial communities in recent years.

Most nanophase materials are fabricated either from the liquid state, or the aerosol state, although some routes combine the two.  The liquid route perhaps gives more control over the process in some cases.  However there is a general feeling at the present that using aerosols is an inexpensive and versatile route to constructing these materials.  Although there are many different production methods being explored, the general approach is to generate, capture and process an aerosol of particles with the dimensions of the final nanostructure.  Typically this requires the generation of particles from 1 to 2 nm in diameter up to around 20 – 30 nm in diameter, depending on the required properties of the final material.  Generation rates in research laboratories tend to be low (of the order of mg/hour), although where industrial production of nanoparticles has commenced, production rates of the order of tonnes per hour are seen.

At present, nanophase materials are an emerging technology, with the emphasis most definitely still on the research lab.  However, there is considerable commercial commitment to the field, and it is certain that as scale-up problems are overcome, the mass production of both nanoparticles and nanophase materials will increase rapidly world-wide.  When this occurs, the unique health problems associated with a unique product that can neither be treated as a bulk material or on a molecular level will have to be fully addressed.  In the meantime, there is a clear need to keep up to date with both developments in the technology, and any health concerns that may be associated with it.

Over the past ten years, commercial-scale production of nanoscale materials has moved on significantly, although perhaps not as much as some would have predicted.  Yet the issues surrounding their safety still reflect (by on large) the issues raised here.

The report summarizes the state of nanotechnology research in 1999—which I’ll skip over—and goes on to consider where the rather quaintly termed nanophase technology was heading:

The indication from the scientific press is that there are as many potential applications for nanophase technology as there are groups working in the field.  However a relatively small number of areas can be identified where commercial production of materials is most likely to be seen in the next 5 – 10 years.  To understand the commercial pressure behind the progress of nanophase technology and its likely integration into industry, you only have to consider the potential market for successful applications.  In the electronics industry in particular, the revenue arising from nanotechnology is likely to be well in excess of hundreds of billions of dollars.  In other areas, such as coatings and catalysts, similar markets exist for successful applications.  The market for ‘intelligent’ drug delivery systems, if successful, is likely to be immense.  Reflecting this, the pharmaceutical industry is currently investing in excess of $14B per annum into advanced delivery systems.

Electronic applications

The reduction in particle size has a profound effect on electronic structure as nanometre dimensions are reached, leading to a number of unique electronic properties seen in individual and groups of nanoparticles.  As an illustration, Si, which is semiconducting in the bulk solid, may be used to form nanometre sized pseudo-crystals with one of two types of atomic structure dominating its faces.  Particles with one structure are fully conducting. Those with the other are good insulators. What does this mean/what are the general implications?

Perhaps the most widely recognised electronic property of nanoparticles is their ability to act as quantum dots.  In arrays of such particles, the overall electronic characteristics are dominated by quantum effects within the particles, leading to novel applications.  For instance, quantum dot devices can be used to create high efficiency LED’s and electroluminescent plastics.  High frequency solid state lasers based on quantum dot technology are expected to form the basis of a major breakthrough in telecommunications, leading to significantly higher communication bandwidths.  High speed and high capacity computer memory will also be possible using quantum dot technology.  Success in fabricating viable quantum dot devices will bring about a major technological step within the electronics industry, leading to a $B production industry, although progress at present is limited by the need to fabricate very precise arrays of well characterised particles.  Current approaches include the use of colloids, nanolithography and aerosols.

Porous nanostructured semiconductors such as silicon have recently been shown to have electroluminescent properties.  If this can be fabricated into integrated circuits, the basis for the next generation of high speed optoelectronic computers will be laid.  Nanoparticles are also being found to lead to improved properties in resistors and capacitors.  Ultrafine conducting particles embedded in an insulating matrix have been shown to give a great range of resistances as well as showing very high temperature stability.  Similarly, the use of nanoparticles in capacitors has been shown to give a high dielectric permitivity and a low dissipation factor, making them ideal for high speed computer memory.

A particularly interesting phenomenon seen in nanophase materials is that of electrochromism; the modification of optical properties by the application of an electric field. Windows or mirrors coated with thin layers of these materials show variable light transmittance or reflection based on the magnitude of an applied electric field.  It has also been found that nanophase materials may be used to form thin transparent films with high conductivity.

A number of other important areas relating to electronics are increasingly relying on the use of nanostructured materials.  Solid state gas sensors show improved sensitivity when using films of sintered nanometre particles; high temperature superconductors have a higher performance when formed of nanostructured materials; thermocouples benefit from nanostructure and the magnetic properties of some nanostructured materials is already exploited to the full in magnetic storage media.

Coatings

Using nanophase materials to coat a wide range of substrates is being explored, and has been exploited in a wide range of applications.  Hard nanophase coatings are important in the construction industry.  The use of coatings with specific optical properties is of interest within the glass and photographic film industries.  Dry coating technology is also benefiting from nanophase materials.  It has been shown that the transport properties of large particles may be radically altered by the addition of a thin coating of fine particles of a suitable material.  For instance, coating starch grains with fumed silica results in a highly flowable powder.  In many cases, this coating need only be of the order of nanometres thick, and the use of nanoparticles in dry coating processes is already under investigation.

Chemical-mechanical polishing using nanoparticle slurries.

Surface polishing is a critical step in the processing of silicon wafers prior to semiconductor chip fabrication.  Surface blemishes are a major source of both wafer and chip rejection in the electronics industry.  By using polishing slurries consisting of nanoparticles, planarisation of wafer surfaces with fewer blemishes is possible.

Drug delivery systems.

A key goal in current drug delivery system research is the development of ‘intelligent’ systems that will deliver doses to specific sites within the body.  One approach being actively considered is the use of coated nanoparticles.  These would be capable of penetrating capillaries and being transported directly to the target site.  The coating would include the drug to be delivered, components to prevent an immune response from the body and components to achieve site-specific or condition-specific delivery.

Nanoparticle catalysts

The modified surface chemistry of nanoparticles is well recognised for its catalytic properties in many materials.  This, together with the associated surface area to mass ratio for such particles, has led to intense interest in nanostructured catalysis within many fields.

After laying out the state of the science regarding the potential risks of inhaling nanoscale particles (which has advanced considerably over the past ten years), the report summarises (on the health impacts):

There has been little work in this field to date, so it is difficult to draw meaningful general conclusions from the published data. One of the reasons for this lack of data appears to be the difficulty in generating particles of standard and known size for use in in vitro studies. Particles used in both in vitro and in vivo studies have also tended to be relatively poorly characterised. Different effects both in vitro and in vivo have been observed with different sources of ultrafine particles, so the responses measured may be a function of the particle constituents rather than the particles per se. The differences observed have been attributed to the ability of particles with a particular composition to have different levels of free radical activity at their surface. Whilst there has been some work investigating synergy between acid aerosols and ultrafine particles (see below), there has been no work investigating the synergy between ultrafine particles and other potential airborne contaminants, e.g. allergens, VOC’s and bacteria. Some of the animal models used to demonstrate toxicological endpoints require exposure regimes which are far in excess of any possible exposure in humans (e.g.  6 hours a day, 5 days a week for 3 months). Therefore, the extrapolation of such health effect data to humans should be treated with some caution.
…
Interest in possible health effects following inhalation of ultrafine particles is high at present, and research is beginning to follow this interest.  Inhalation toxicology has taken over from epidemiology over the past few years, and dominates the field at present.  Dose response relationships in rodents are being seen that indicate particle number or surface area to be more appropriate metrics than mass.  The possibility of ultrafine particles acting as vectors to transport  acids and metals to the alveolar region of the lung is also being explored.  However it is recognised that many of the current approaches being taken are lacking in various aspects, particularly regarding the significance of chosen endpoints and the characterisation of particle exposure, and a number of groups are now beginning to address these issues.  This is an area that is particularly ripe for good research proposals to sympathetic funding bodies. The need to fully characterise the particles used in exposure and inhalation tests, as well as those that people are exposed to in the workplace and environment, is well understood, although the right combination of technical skills to achieve this seems to be lacking in many establishments.  In particular there would appear to be significant scope for transferring analytical electron microscopy skills used in materials science and nanostructure analysis to the analysis of ultrafine aerosol particles.  There is also a recognised need for in-vitro test systems that allow cell cultures to be exposed to the aerosol, rather than a particulate suspension.  A small number of research groups are currently developing test systems allowing direct aerosol deposition.  Funding for fine particle research (PM2.5 sampling, and mass-based aerosol sampling) still dominates, but all aspects of ultrafine particle research are on the increase, and it is likely that the next few years will see significant funding opportunities and research in this area.  Driven by concerns over environmental exposure, together with the need to address exposure limits for nuisance dusts, there is increasing interest in examining the impact of ultrafine particle exposure in the workplace.

The report covers a lot of ground on exposure measurement and control, which I won’t duplicate here (although a lot of the information remains highly pertinent).  Instead, I’ll jump right to the end of the report, where a number of research recommendations are made.  Remembering that these are focused specifically on inhalation exposure in the workplace, they sound surprisingly contemporary, being written 10 years ago:

Full quantification of ultrafine aerosol exposure in the workplace:

• Measurement of number, size, surface area, composition, morphology, structure
• Investigation of the surface properties of workplace particles.
• Investigation of surface enrichment, role of modified surface activity below 10 nm, relevance of internal structure.
• Development of instrumentation and analytical techniques for surface area
• measurement and individual particle characterisation (Analytical Electron Microscopy)

Targeted epidemiology and toxicology studies.

• Epidemiological evidence for ultrafine particle toxicity in the workplace
• Toxicity of well defined particles, and of particles characteristic of those found in the workplace.
• Investigation of mechanisms resulting in toxic responses, in relation to the known physical and chemical attributes of workplace particles.

Instrumentation

• Identification of deficiencies in instrumentation and monitoring requirements, and development of new technologies and methods.

Control

• Reassessment of  the applicability of conventional control systems (including RPE) to reduce exposure to ultrafine particles, and the development of new approaches to exposure control.

Exposure Limits

• Assessment of current exposure limits in the light of available data on ultrafine particle toxicity, and the development of more appropriate approaches to exposure limits.

Ten years on, it is surprising how relevant this document still is.  The major issues facing the safe use of nanomaterials were reasonably clear ten years back.  And many of the research needs raised then remain today.  Progress certainly has been made since then, and an understanding of the types of nanomaterials of greater concern has increased—the 1999 report doesn’t mention carbon nanotubes for instance.  But on the flip side, this is a report that was clearly unencumbered by the politics of nanotechnology that seem to have diffused through things today

Perhaps most surprisingly though, is that governments and others are still talking about the same issues – often as if they have discovered them for the first time – without doing that much about them.  It would be churlish to ask where we might have been now if some of those 1999 recommendations were listened to.  But at least I can ask where we might be in 2019, if only we can break out of this endless cycle of re-inventing the nanotech risk report!

Endnote

Because this was an internal report, I have been careful to extract only parts of it that are of general interest and are not in any sense proprietary.  That said, there is a lot of information in the full report that would be helpful to anyone grappling with addressing and managing potential occupational risks arising from nanoscale particle exposure in the workplace.  It would be great if the UK Health and Safety Executive could release it for public use!

References

COMEAP (1996).  Non-biological particles and health.   HMSO Publications.

Dochery, D. W., Pope, C. A., Xu, X., Spengler, J. D., Ware, J. H., Fay, M. E., Ferris, B. G. and Speizer, F. E. (1993).  An association between air pollution and mortality in six U.S. cities.  N. Engl. J. Med, 329, 24, 1753-1759.

Donaldson, K. and McNee, W. (1998).  The mechanics of lung injury caused by PM10.  In: Air Pollution and Pealth.  Eds:  Hester and Harrison.  Royal Society of Chemistry.  ISBN 0-85404-245-8.  pp21-32.

Lison, D., Lardot, C., Huaux, F., Zanetti, G. and Fubini, B. (1997).  Influence of particle surface area on the toxicity of insoluble manganese dioxide dusts. Arch. Toxicol. 71, 725-729

Oberdörster, G., Gelein, R. M., Ferin, J. and Weiss, B. (1995).  Association of particulate air pollution and acute mortality:  involvement of ultrafine particles?  Inhal. Toxicol., 7, 111-124.

Pekkanen J, Timonen KL, Ruuskanen J, Reponen A, Mirme A (1997) Effects of ultrafine and fine particles in urban air on peak expiratory flow among children with asthmatic symptoms. Environ Res 74: 24-33

Pope, C. A. (1996).  Adverse health effects of air pollutants in a nonsmoking population.  Toxicology, 111, 149-155.

Schlesinger, R. B. (1995).  Toxicological evidence for health effects from inhaled particulate pollution:  does it support the human experience?  Inhal. Toxicol., 7, 99-109.

Schwartz, J., Spix, C., Wichmann, H. E. and Malin, E. (1991).  Air pollution and acute respiratory illnessin five German communities.  Environ. Res., 56, 1-4.

Schwartz, J., Slater, D., Larson, T. V., Pierson, W. E. and Koenig, J. Q. (1993).  Particulate air pollution and hospital emergency room visits for asthma in Seattle.  Am. Rev. Respir. Dis., 147, 826-831.

Seyton, A., MacNee, W., Donaldson, K. and Godden, D. (1995).  Particulate air pollution and acute health effects.  The Lancet, 345, 176-178.

Nanotechnology: What is it, what can it do, what are the downsides, and how can we ensure it reaches its full potential?

Managing the Small Stuff. Also available in High Definition on Vimeo

The promise and challenges of nanotechnology is something I lecture on a lot.  And when I do, I’m inevitably asked for a copy of the slides.  But here I have a problem: I have a rather idiosyncratic lecture style that moved on from the 3-bullet point PowerPoint straitjacket some years ago—which is great for the live performance, but lousy when it comes to handing out intelligible PDF’s of the talk.

So with the help of my trusty Mac and YouTube, I’ve been experimenting with other ways to capture the essence of these lectures.  The video above is the first result—a short primer on nanotechnology:

First, let me stress that this is an experiment… I’m not sure whether it succeeds in conveying anything useful about nanotechnology, or whether it ends up being rather crass and unintelligible.  But I would love some feedback.

You’ll notice as you watch the video above (if you are observant) that I eschewed a simple movie of myself giving a lecture.

Why?

Well, would you sit and watch me droning on about nanotechnology for more than a few seconds?  I wouldn’t!

Actually, this would have been easier to pull off than what I ended up doing, but I was more interested in how the presentation medium (Keynote on the Mac) and the internet (YouTube in particular) could be used to convey information in a more innovative and accessible way.  If you are reaching out to a non-specialist audience, to what extent do eye-catching visuals and a soundtrack make the experience more informative and enjoyable?  Again, I’m not sure—but that is all part of what I am trying to find out.

(I should add here that rumors of this whole exercise just being an excuse to play with Keynote’s fancy graphics capabilities are entirely unfounded…)

The resulting video is rather short—it’s an unashamedly high-level view of nanotechnology that avoids specifics, and instead focuses on underlying concepts.  This seems to be a format that lends itself to conveying general information in small chunks.  I’m still tossing up whether to try formatting and posting a full 60 minute lecture in this style, but my gut tells me that this could end up being the YouTube equivalent of Vogon poetry—something no-one should have to endure!

The bottom line here (to get serious for a second) is that compiling animated movies from presentations and posting them on the web does seem to offer new opportunities for us amateur communicators to convey information on science in an accessible and informative way, using readily available tools.  I suspect that if it’s done well, this could be an effective way of packaging information to reach a broad audience.

I’m not sure how successful the movie above is in conveying what nanotechnology is all about to a lay audience.  But I do think it demonstrates the possibility of using today’s digital technology to convey complex information in new ways.  And as science and technology become increasingly important within society, we certainly need innovative ways to bridge the gap between those who generate new knowledge, and those who use it.

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Technical Stuff

The original presentation was developed in Keynote on a MacBook Pro.  A confession here—I really like the simplicity, utility and visual appeal of Keynote, and develop all of my presentations using the package.  Using PowerPoint just makes me miserable in comparison.

Most of the slides in the presentation were culled from previous lectures I have given, but were formatted specifically for this video.  In particular, animations within and between slides were added to help the story develop as the video progresses.  The slides were formatted at a resolution of 1280 by 720 pixels, allowing them to be saved as a high definition video.

The final presentation was exported as a movie and—you’ve got to love the integration on Macs—imported into GarageBand to allow soundtrack and commentary to be added.  The soundtrack is from my own doodling within GarageBand—for which I must apologize.  The end movie was exported, and uploaded to YouTube.

Finally, first time round I did this, I just included the slides and the soundtrack in the movie.  The result was artistically intriguing—but surreal, cryptic, and ultimately unfathomable – if you don’t believe me, check out the video below.  Which is why I ended up adding the commentary.  But it still makes interesting, if somewhat obscure, viewing.  Whether it makes any sense or not, I hope you enjoy it!

Managing the Small Stuff – without the commentary. Also available in High Definition on Vimeo

The Royal Commission on Environmental Pollution report on Novel Materials

Imagine for one naïve moment that we have a pretty good handle on managing the environmental impact of existing manufactured “stuff”.  Then someone comes along and invents some “new stuff” that behaves very differently from the “old stuff.”

How can we be sure that the frameworks and mechanisms in place for preventing harm to the environment will work for the new stuff?  And where they are strained to breaking point, how do we go about fixing the system?

These are two questions addressed in a new report from the Royal Commission on Environmental Pollution—an independent British standing body established in 1970 to advise the Queen, government, Parliament and the public on environmental issues… Of course, because this is for the Her Majesty The Queen, phrases like “old stuff” and “new stuff” are conspicuous by their absence in the report—which instead addressed the rather more sophisticated-sounding issue of “Novel Materials in the Environment.”

This is, in effect, a report on the challenges of avoiding adverse environmental impacts of engineered nanomaterials.  Coming four years after the seminal report from the Royal Society and Royal Academy of Engineering on nanoscience and nanotechnologies, it reflects both how thinking on the challenges and opportunities presented by engineered nanomaterials has advanced, and actions to ensure their safe use have not!

The report itself draws on extensive interviews with experts around the world, and the depth and quality of the writing reflects this.  Perhaps not surprisingly, many of the recommendations arising from this process will be familiar to readers—the challenges haven’t changed that much over the years, and solutions still seem few and far between in many cases.

But familiar as many (not all) of the recommendations are, they are still important to the sustainable development of emerging nanotechnologies, and bear re-iterating.

And there are three in particular that are worth calling out:

Functionality: we need to focus on the properties and functionalities of specific nanomaterials as the key driver rather than treat all materials in the size range as one single class.

To my mind, this is the single most important conclusion to arise from the report.  It moves the debate on environmental impact away from generic nanomaterials—an ill-defined class of materials that have no unifying impact-relevant characteristics—towards materials that present unconventional risks due to novel behaviour.  This is a smart move, as it opens the door to addressing materials that have the potential to cause harm in ways that are not covered by conventional understanding, and avoids endless (and usually fruitless) discussions on what defines a nanomaterial.

Essentially, the Royal Commission have stated that it is not what you call a material that is important, but what it does.

Of course, there is still the issue of what defines a “novel material.”  While I’m sure this will be debated to death in certain quarters, here are some pointers from the report.  Novel materials are:

• New materials hitherto unused or rarely used on an industrial scale, such as certain metallic elements (e.g. rhodium, yttrium, etc.) and compounds derived from them;
• new forms of existing materials with characteristics that differ significantly from familiar or naturally-occurring forms (e.g. nanoforms of silver and gold that exhibit significant chemical reactivity, enhanced biocidal properties or other properties not manifest in the bulk form);
• new applications for existing materials or existing technological products formulated in a new way, which may lead to substantially different exposures and hazards from those encountered in past uses (e.g. the use of cerium oxide as a fuel additive); and
• new pathways and destinations for familiar materials that may enter the environment in forms different from their manufacture and envisaged use (e.g. microscopic plastic particles arising from mechanical action in marine ecosystems).

Information: we need to establish directed research programme on the properties and functionalities of materials in order to inform risk assessment and risk management strategies.

There’s nothing new here.  The Royal Society and Royal Academy of Engineering said as much in 2004, and I have gone on record repeatedly stressing the need for strategic research programmes.  But the fact that the Royal Commission on Environmental Pollution pulled this out as one of their three main priorities highlights how little is still being achieved in this area.

Maybe this time, someone will listen.

Adaptive management: we need to recognise the degree of ignorance and uncertainty and the time it will take to address these (insofar as they can be addressed). We also need to develop flexible and resilient forms of adaptive management to allow us to handle such difficult situations and emergent technologies.

Whichever way you look at things, conventional approaches to risk assessment and management are unlikely to work in the short term for novel materials.

Materials that behave in unconventional ways will always be developed faster than a deep knowledge of how they interact with and impact on human health and the environment.  And any attempt to avoid managing risks until a full and complete conventional risk assessment has been conducted will jeopardize innovation, people’s health and the environment.  This doesn’t mean that quantitative risk assessment needs to be abandoned—it is still the best tool we have for making evidence-based decisions on reducing and managing potential harm.  But in the short term, novel approaches are needed to managing risks, to avoid undue harm without stifling innovation.

For instance, if you are manufacturing carbon nanotubes, you cannot wait ten years for government agencies to set hard and fast exposure limits—you need guidance now on effective ways to reduce potential risks if you are to have a hope of getting viable products out of the door.  And that means taking unconventional approaches to establishing pragmatic, flexible acceptable exposure levels that are based on the best available information.

The results may not be as robust as what regulators will come up with in several years’ time.  But I can guarantee that they will help the manufacturer protect the workforce without being crippled by unnecessary investment in control and containment technologies.

This is just one example of where flexible and resilient forms of adaptive management can both protect people and the environment while enabling the sustainable use of novel materials—there are many more.

And as the Royal Commission recognizes, the increasing pace of innovation means that such innovative approaches to risk management are going to become more and more important.

We recommend that it is desirable to move beyond one-off public engagement ‘projects’ to recognise the importance of continual ‘social intelligence’ gathering and the provision of ongoing opportunities for public and expert reflection and debate. We see these functions as crucial if, as a society, we are to proceed to develop new technologies in the face of many unknowns.

This is a specific recommendation in the report rather than an overarching recommendation (as the first three points were).  But it is worth highlighting, because the interplay between society, science and technology is only going to get more complex over the coming years.  And the sustainable development of any new technology is going to have to factor in new directions in the “democratization of science and technology.”

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Overall, this is an important report, and one that should be taken seriously.  It represents an evolution in thinking rather than a step-change (with perhaps the exception of re-framing the debate over nanomaterials in terms of novel materials).  But nevertheless it makes clear recommendations that are essential to the safe and successful use of engineered nanomaterials.

But back to the “stuff.”  ‘New stuff” (novel materials) is essential to solving global challenges that the “old stuff” we have to hand simply cannot handle.  And these are big challenges that include renewable energy, global warming, water purification and disease treatment.  But as the Royal Commission on Environmental Pollution implies, new stuff requires new ways of doing business if we are going to see the benefits while avoiding potential pit-falls.

And at the end of the day, this means thinking innovatively about research, risk management and reaching out to citizens and other stakeholders.

How cool is this: A nanotech-enabled labcoat to protect the user against… well, nanomaterials presumably, amongst other things!  

The labcoat—which uses Nanotex technology to make it stain resistant—is part of a major update to the Project on Emerging Nanotechnologies Consumer Products Inventory that tracks manufacture-identified nano-products.  Other eye-catchers in the update include a hunting shirt that resists bloodstains, a nanotech-based adhesive for McDonald’s burger containers, and an oven-like device for sanitizing whiffy shoes.

Of course, there are plenty of people who feel that consumer products represent an altogether too trivial side of nanotechnology.  And I have to agree that on the scales of virtue, a nano-silver bidet would find it hard to compete with the next generation of nano-enabled solar cells or targeted cancer drugs.  Yet trivial as many of the 800+ products in the updated inventory may seem, this is where most people will probably first come across the technology, and start to form their early opinions on whether it’s a good thing, or not so good.  

And in this bizarrely-connected world within which we live, good experience with nano-bidets (for example) are more likely than not to make the introduction of nano-cancer drugs go just that little bit smoother.

But beyond initial impressions, consumer products in their broadest sense are where some of the first widespread exposures to engineered nanomaterials are likely to occur.  And this means that care is needed over how nanomaterials are used in these products, and how that use is monitored and regulated.  

In the US, the Consumer Product Safety Commission (CPSC) is responsible for protecting the public against unreasonable risks of injury or death associated with consumer products.  But recently, the CPSC has been struggling with low-tech problems like lead in children’s toys, and there is concern that this doesn’t bode well for the agency’s ability to tackle high tech nanotechnology-based products.

This is the conclusion of a new report by E. Marla Felcher of Harvard University’s Kennedy School.  In “The Consumer Product Safety Commission and Nanotechnology,” published by the Project on Nanotechnologies, Felcher paints a picture of CPSC as an agency of lofty ideals, crippled by a lack of political support, dwindling resources, inadequate scientific expertise and inadequate authority.  In the report’s executive summary, she writes

“CPSC’s inability to carry out its mandate with respect to simple, low-tech products such as Thomas the Tank Engine toy trains, Barbie dolls and Easy-Bake Ovens bodes poorly for its ability to oversee the safety of complex, high-tech products made using nanotechnology. The agency lacks the budget, the statutory authority and the scientific expertise to ensure that the hundreds of nanoproducts now on the market, among them baby bottle nipples, infant teething rings, teddy bears, paints, waxes, kitchenware and appliances, are safe. This problem will only worsen as more sophisticated nanotechnology-based products begin to enter the consumer market.”

The critique is harsh—all the more so because CPSC staff are clearly trying hard to get their heads around the challenges that nanotechnology is presenting them with.  Yet according to Felcher, the problems lie not so much with the staff as with the agency’s lack of information, resources and authority.  To ensure CPSC is nano-ready (and more broadly, emerging technology-ready), she recommends that:

• The agency’s knowledge-base is built-up,
• that CPSC work closely with other health and safety agencies,
• that information on nano-products is solicited from companies,
• that a Chronic Health Advisory Panel is convened to evaluate potential risks associated with nano-products for children,
• that the agency appeal to industry to develop voluntary safety standards for children’s products,
• and that the US congress take action on the Consumer product Safety Act bill to increase CPSC’s authority to address products based on new and emerging technologies.

There’s a good chance that many of the allegedly nanotechnology-enabled products entering the market are harmless (or at least, mostly harmless).  But a combination of novel and sometimes unpredictable material behaviour, few checks and balances to use and an inadequately resourced and empowered regulator seems like a dangerous combination; when a potentially harmful nano-product does come along, there aren’t, it seems, many barriers to prevent problems from occurring.  

And we are still dealing with very simple nanotechnologies—nanoparticles of silver, titania and carbon in the main.  What happens when consumer product manufacturers start to use more complex nanotechnologies?

OK so nano-consumerism may seem rather trivial in the grand scheme of things.  But the impacts of nano-consumerism gone wrong could be far from inconsequential.  So if we want to see the less trivial products of nanotechnology—the renewable energy sources, the high performance batteries, the smart drugs—now might be a good time to make sure the first waves of products perform well without causing harm.

Now, back to that shoe de-whiffer—I think my “nano  silver far infrared  anti-odor healthy socks” need a little help…

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This post first appeared on the SAFENANO blog in August 2008

As the rate of technological progress advances, are we learning the lessons of past successes and failures?  And are we applying these lessons successfully to nanotechnology? 

In 2001, the European Environment Agency (EEA) published a seminal report on developing emerging technologies responsibly.  Through a series of fourteen case studies spanning the past century, a panel led by the late Poul Harremoës examined what has gone right and what has gone wrong with the introduction of past technologies, and what can be learned about introducing new technologies as safely and as successfully as possible.  

The resulting report, “Late lessons from early warnings: the precautionary principle 1896-2000” (PDF, 1.7 MB) draws twelve “late lessons” for decision-makers faced with addressing emerging technologies [1].

Although the report was written before nanotechnology hit the big-time, the twelve lessons (listed below) resonate strongly with the challenges of fostering innovative yet responsible nanotechnologies.  So much so in fact a new commentary just published on-line in the journal Nature Nanotechnology takes a hard look at how nanotech measures up to the report’s findings.  

“Late lessons from early warnings for nanotechnology” (Hansen, Maynard, Baun and Tickner (2008),  DOI:10.1038/nnano.2008.198) systematically compares progress in nanotechnology with each of the EEA’s twelve lessons, and assesses where progress is being made, and where we could be doing better.   

And the findings?  Some of the lessons have begun to sink in, but overall, it looks like a refresher course in responsible nanotechnology wouldn’t go amiss.

In the commentary, we conclude:

“The picture is not as bleak as it could be. While progress towards developing sustainable nanotechnologies is slow, we do seem to have learnt some new tricks: asking more critical questions early on; developing collaborations that cross discipline, department and international boundaries; beginning the process of targeting research to developing relevant knowledge; engaging stakeholders; and asking whether existing oversight mechanisms are fit for purpose.

But are we doing enough? The question seems not to be whether we have learnt the lessons, but whether we are applying them effectively enough to prevent nanotechnology being one more future case study on now not to introduce a new technology. Despite a good start, it seems that we have become distracted on the way – nanotechnology is being overseen by the same government organizations that promote it; research strategies are not leading to clear answers to critical questions; collaborations are not being as productive as is needed; and stakeholders are not being fully engaged. In part this is attributable to bureaucratic inertia, although comments from some quarters – such as “risk research jeopardizes innovation” or “regulation is bad for business” — only cloud the waters when clarity of thought and action are needed.

If we are to realize the commercial and social benefits of nanotechnology without leaving a legacy of harm, and prevent nanotechnology from becoming a lesson in what not to do for future generations, perhaps it is time to go back to the class-room and re-learn those late lessons from early warnings.”

Nanotechnology is all about the future.  But it seems an occasional glance back in history is needed to set the best course of action for success.

EEA’s Twelve Late Lessons:

1. Acknowledge and respond to ignorance, uncertainty and risk in technology appraisal. 

2. Provide long-term environmental and health monitoring and research into early warnings. 

3. Identify and work to reduce scientific ‘blind spots’ and knowledge gaps. 

4. Identify and reduce interdisciplinary obstacles to learning. 

5. Account for real-world conditions in regulatory appraisal. 

6. Systematically scrutinize claimed benefits and risks. 

7. Evaluate alternative options for meeting needs, and promote robust, diverse and adaptable technologies. 

8. Ensure use of ‘lay’ knowledge, as well as specialist expertise. 

9. Account fully for the assumptions and values of different social groups. 

10. Maintain regulatory independence of interested parties while retaining an inclusive approach to information and opinion gathering. 

11. Identify and reduce institutional obstacles to learning and action. 

12. Avoid ‘paralysis by analysis’ by acting to reduce potential harm when there are reasonable grounds for concern. 

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[1]  At the time of posting, the direct link to the “Late Lessons” report was down (that link ishttp://reports.eea.europa.eu/environmental_issue_report_2001_22).  As an interim measure, I have linked to a copy of the report posted at www.genok.org.

This post first appeared on the SAFENANO blog in July 2008

Why nano?  Why care?  For non-nanotech initiates, an obsession with nanotechnology must sometimes seem a bizarre occupation of the sad and lonely.  And even within the nanotechnology community, who hasn’t had occasional doubts over the legitimacy of singling out “nano” as something special?  Yet occasionally a piece of work comes along that helps put things back into perspective.  For me, a paper just published on-line in the journal Nano Letters did exactly that.

To be quite frank, the paper’s title is not what I would call inspirational.  But dig below the surface, and you unearth an object lesson in what makes nano so intriguing, and why taking a fresh look at possible health and environmental impacts is so important.  First the science though.

The Science

The paper in question is “Controlled Manipulation of Giant Hybrid Inorganic Nanowire Assemblies” by Fung Suong Ou, Manikoth M. Shaijumon, and Pulickel M. Ajayan, published on-line in Nano Letters, May 29 2008.  Unfortunately, a subscription to the journal is needed to view the paper, but the supplemental information is freely available (here), and well worth looking at.  

In brief, the authors used a nanoscale fabrication technique to construct long, straight, carbon nanotubes capped with gold nanowires.  Think “magician’s wand” with the nanotube as the stem and the gold as the white tip, and you will get the idea.  The nano-wands (for want of a better description) were between 100 nm and 150 nm wide, and over 100 mircometres (100,000 nm) long.  Micrographs in the paper show rafts of uniform-length nano-wands stacked side by side, with individual wands fraying off at the edges.

But this is where things get interesting.  These long, straight artificial rods were designed to have one end that was hydrophobic (water-repelling; the carbon end), and one end that was hydrophilic (water-seeking; the gold).  When dispersed in water, these wands formed a uniform suspension.  But when an organic solvent—dichloromethane (DCM)—was added to the mix, the nano-wands assembled into shells around the DCM, with the black carbon nanotubes facing in and the gold tips facing out.  With a bit of shaking and ultrasonic agitation, one large gold-coloured sphere was formed, separating the DCM from the water.  Reversing the process by suspending the nano-wands in DCM and adding water, a large black sphere assembled; separating the water from the organic solvent.  Black, because in this case the carbon nanotube “tails” were pointing outward.

Using the same fabrication technique, the researchers demonstrated a couple of other tricks.  By adding a band of the metal nickel below the gold tip, the nano-wands could be made magnetic—so now the spheres separating the two liquids could be moved around using a magnetic field.  And by adding an ultraviolet light-degradable hydrophobic chemical to the gold end of nano-wands, spheres were constructed that quite literally turned inside-out under UV irradiation.

The Promise

Nanotechnology is all about functionality—making materials and products that behave in new and unusual waysbecause they have been engineered at an incredibly fine scale.  This new and unusual behaviour might in some cases be due to the unusual physics and chemistry of small clusters of atoms (such as the size-related fluorescence of quantum dots).  But it can just as easily arise from engineering a material at such a fine scale that it can be used in new ways (such as making antimicrobial silver particles small enough to be incorporated into a miscellany of products); or constructing materials at the nanoscale with such sophistication that new properties emerge (multi-functional nano-therapeutics for instance).  The nano-wands are most definitely in the latter categories—their functionality arises from their smallness and sophistication.  

The important point here is that, while size matters, performance matters more.  And so while these nano-wands are technically larger than the 100 nm limit usually (and somewhat arbitrarily) imposed on nanotechnology, they nevertheless represent an ability to create a novel functional material through sophisticated engineering at a very fine scale.

And what functionality!  This is a crude material compared to what could be achieved using similar construction techniques, but even so the nano-wands behave in a most unusual way.  Functionally, they are reminiscent of polar molecules, and the spheres they form are analogous to micelles—“capsules” formed by organic molecules with opposing hydrophobic and hydrophilic ends.  But by engineering them at the nanoscale out of inorganic materials, structural and functional possibilities open up that are way beyond the realm of chemistry alone.  

It is easy to imagine how this material could be used to encapsulate and collect chemical spills in the environment.  Or deliver drugs to where they are needed in a very targeted way (only releasing their payload by disassembling when the right signal is received).  Yet the work of Fung Suong Ou and colleagues hints at much greater things.  Using the same basic technology, there is nothing to prevent the construction of multi-component nanomaterials that can assemble and re-assemble in many different ways, depending on their environment and the stimuli they receive.  As the paper’s authors’ conclude, 

“This controlled engineering feat at the nanoscale that allows well-controlled assembly and manipulation could lead to the creation of smart materials that are a cornerstone for the development of nanotechnology-based applications.”

The challenge

But stimulating as the science is, this paper is also an object lesson in why new thinking is needed on possible risks to human health and the environment, if such technologies are to succeed.

First and foremost, the paper comes hot on the heels of Poland et al.’s study linking some forms of multi-walled carbon nanotubes to precursors of mesothelioma—a disease more usually associated with asbestos exposure.  Poland’s research suggests that carbon nanotubes which are thin, longer than 15 – 20 micrometres, straight, and dispersible, could lead to the disease if inhaled.  The nano-wands in the Ou et al. paper are around 150 nm in diameter, something over 100 micrometres long, straight, and apparently dispersible—in other words, exactly the types of fibres which Poland’s work suggests more research is needed on before the possible health implications are understood.

It’s too early to tell whether Ou’s nano-wands will have their own unique risk-profile.  But their inevitable comparison with the nanotubes used in Poland’s study and the possibilities of dispersive use hinted at in the accompanying press release do raise important questions about their safety.  The important point here is not that this particular material might show harmful behaviour, but that there is always the chance that novel behaviour can lead to unanticipated harm—unless the right questions are asked early on.  And this most definitely requires new thinking on what those questions are, and how they might best be answered.

The second object lesson in new challenges concerns regulations.  Unless used as a drug or pesticide, substances are typically regulated according to their chemical makeup.  It’s an approach that was developed at a time when the terms “chemical” and “substance” were interchangeable.  But Ou’s nano-wands challenge this paradigm.  

These nano-wands and other hybrid substances have no unique chemical identity, and so potentially slip through the net of many existing regulations.  Yet they display a functionality that depends on their physical form and complex makeup, which is not predictable from their chemical components.  And regulations are needed that recognize this.  If effective approaches are to be developed to ensure the safe use of this emerging class of material, new thinking is needed on how substances are classified and regulated.

The bottom line

Why nano? As Ou’s work shows, we can potentially do things with nano that are way beyond any other technology at our disposal.  And when nano is combined with other technologies like biotech and information tech, the possibilities become endless.

Why care?  Because nano will change your life, whether you like it or not.  And you might want to make sure that it is a change for the better, not for the worse.

And the nano-wands?  These have tremendous potential as an innovative new material.  Lets hope that their development is matched by equally innovative thinking on using them safely.

Further resources

Paper: Controlled Manipulation of Giant Hybrid Inorganic Nanowire Assemblies

Supplemental Material to the paper

Managing the Effects of Nanotechnology.  J. Clarence Davies

Paper: Carbon nanotubes introduced into the abdominal cavity of mice show asbestos-like pathogenicity in a pilot study

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This post first appeared on the SAFENANO blog in May 2008