Month: October 2008

Books that inspired me

I’ve just done a brief interview with a journalist for the BBC’s Focus magazine, about the three popular science books on nanotechnology that have most inspired me. I’ve already written about my nanotechnology bookshelf, but this time when I came to choose my three favourite books to talk about it turns out that they weren’t directly about nanotechnology at all. So here’s my alternative list of three non-nanotechnology books that I think all nanotechnologists could benefit from reading.

The New Science of Strong Materials by J.E. Gordon. To say that this is the best book ever written about materials science might not sound like that high praise, but I was hugely inspired by this book when I read it as a teenager, and every time I re-read it I find in it another insight. It was first published in 1968, long before anyone was talking about nanotechnology, but it beautifully lays out the principles by which one might design materials from first principles, relating macroscopic properties to the ways in which their atoms and molecules are arranged, principles which even now are not always as well known as they should be to people who write about nanotechnology. It’s a forward looking book, but it’s also full of incidental detail about the history of technology and the science that has underlain the skills of craftsmen using materials through the ages. It also looks to the natural world, discussing what makes materials of biological origin, like wood, so good.

The Self-Made Tapestry by Philip Ball. Part of the appeal of this is the beauty of the pictures, depicting the familiar natural patterns of clouds and sand-dunes, as well as the intricate nanoscale structure of self-assembled block copolymer phases and the shells of diatoms. But alongside the illustrations there is an accurate and clear account of the principles of self-assembly and self-organisation, that cause these intricate patterns to emerge, not through the execution of any centralised plan, but as a result of the application of simple rules describing the interactions of the components of these systems.

Out of Control by Kevin Kelly. This is also about emergence, but it casts its net much more widely, to consider swarm behaviour in insects, economics and industrial ecologies, and flocks of insect-like robots. The common theme is the idea that one can gain power by relinquishing control, harnessing the power of adaptation and evolution in complex systems in which non-trivial behaviour arises from the collective actions of many interacting objects or agents. The style is evangelical, perhaps to the extent of overselling some of these ideas, and some may, like me, not be wholly comfortable with the libertarian outlook that underlies the extension of these ideas into political directions, but I still find it hugely provocative and exciting.

In Richmond, VA

I’m making a brief visit to Virginia to talk to high school students and others about my book, Soft Machines. It’s in connection with a visiting author program for the Chesterfield County school system, initiated by Prof Krishan Aggarwal, from Virginia State University; each year high school students in the County schools get to read a science book in class and the author comes to discuss it with them. So far I’ve talked to students in Monacan High School and L.C. Bird High School, as well as spending an afternoon with the staff of Richmond’s MathScience Innovation Centre and local science teachers, who have been developing sets of lesson materials about nanotechnology for high school students, and have clearly been thinking hard about how to convey some of the developing concepts of nanotechnology to their students. I’m just about to go back to L.C. Bird High School for a public lecture and panel discussion. I’ve been hugely impressed so far by the thought that’s gone into the questions being put to me; it’s been a pleasure to interact with such an engaged group of students. My thanks to Krishan and to Dr Jeremy Lloyd, from the Chesterfield County schools, for setting this up and looking after me.

What’s meant by “food nanotechnology”?

A couple of weeks ago I took part in a dialogue meeting in Brussels organised by the CIAA, the Confederation of the Food and Drink Industries of the EU, about nanotechnology in food. The meeting involved representatives from big food companies, from the European Commission and agencies like the European Food Safety Association, together with consumer groups like BEUC, and the campaigning group Friends of the Earth Europe. The latter group recently released a report on food nanotechnology – Out of the laboratory and on to our plates: Nanotechnology in food and agriculture; according to the press release, this “reveals that despite concerns about the toxicity risks of nanomaterials, consumers are unknowingly ingesting them because regulators are struggling to keep pace with their rapidly expanding use.” The position of the CIAA is essentially that nanotechnology is an interesting technology currently in research rather than having yet made it into products. One can get a good idea of the research agenda of the European food industry from the European Technology Platform Food for Life. As the only academic present, I tried in my contribution to clarify a little the different things people mean by “food nanotechnology”. Here, more or less, is what I said.

What makes the subject of nanotechnology particularly confusing and contentious is the ambiguity of the definition of nanotechnology when applied to food systems. Most people’s definitions are something along the lines of “the purposeful creation of structures with length scales of 100 nm or less to achieve new effects by virtue of those length-scales”. But when one attempts to apply this definition in practise one runs into difficulties, particularly for food. It’s this ambiguity that lies behind the difference of opinion we’ve heard about already today about how widespread the use of nanotechnology in foods is already. On the one hand, Friends of the Earth says they know of 104 nanofood products on the market already (and some analysts suggest the number may be more than 600). On the other hand, the CIAA (the Confederation of Food and Drink Industries of the EU) maintains that, while active research in the area is going on, no actual nanofood products are yet on the market. In fact, both parties are, in their different ways, right; the problem is the ambiguity of definition.

The issue is that food is naturally nano-structured, so that too wide a definition ends up encompassing much of modern food science, and indeed, if you stretch it further, some aspects of traditional food processing. Consider the case of “nano-ice cream”: the FoE report states that “Nestlé and Unilever are reported to be developing a nano- emulsion based ice cream with a lower fat content that retains a fatty texture and flavour”. Without knowing the details of this research, what one can be sure of is that it will involve essentially conventional food processing technology in order to control fat globule structure and size on the nanoscale. If the processing technology is conventional (and the economics of the food industry dictates that it must be), what makes this nanotechnology, if anything does, is the fact that analytical tools are available to observe the nanoscale structural changes that lead to the desirable properties. What makes this nanotechnology, then, is simply knowledge. In the light of the new knowledge that new techniques give us, we could even argue that some traditional processes, which it now turns out involve manipulation of the structure on the nanoscale to achieve some desirable effects, would constitute nanotechnology if it was defined this widely. For example, traditional whey cheeses like ricotta are made by creating the conditions for the whey proteins to aggregate into protein nanoparticles. These subsequently aggregate to form the particulate gels that give the cheese its desirable texture.

It should be clear, then, that there isn’t a single thing one can call “nanotechnology” – there are many different technologies, producing many different kinds of nano-materials. These different types of nanomaterials have quite different risk profiles. Consider cadmium selenide quantum dots, titanium dioxide nanoparticles, sheets of exfoliated clay, fullerenes like C60, casein micelles, phospholipid nanosomes – the risks and uncertainties of each of these examples of nanomaterials are quite different and it’s likely to be very misleading to generalise from any one of these to a wider class of nanomaterials.

To begin to make sense of the different types of nanomaterial that might be present in food, there is one very useful distinction. This is between engineered nanoparticles and self-assembled nanostructures. Engineered nanoparticles are covalently bonded, and thus are persistent and generally rather robust, though they may have important surface properties such as catalysis, and they may be prone to aggregate. Examples of engineered nanoparticles include titanium dioxide nanoparticles and fullerenes.

In self-assembled nanostructures, though, molecules are held together by weak forces, such as hydrogen bonds and the hydrophobic interaction. The weakness of these forces renders them mutable and transient; examples include soap micelles, protein aggregates (for example the casein micelles formed in milk), liposomes and nanosomes and the microcapsules and nanocapsules made from biopolymers such as starch.

So what kind of food nanotechnology can we expect? Here are some potentially important areas:

• Food science at the nanoscale. This is about using a combination of fairly conventional food processing techniques supported by the use of nanoscale analytical techniques to achieve desirable properties. A major driver here will be the use of sophisticated food structuring to achieve palatable products with low fat contents.
• Encapsulating ingredients and additives. The encapsulation of flavours and aromas at the microscale to protect delicate molecules and enable their triggered or otherwise controlled release is already widespread, and it is possible that decreasing the lengthscale of these systems to the nanoscale might be advantageous in some cases. We are also likely to see a range of “nutriceutical” molecules come into more general use.
• Water dispersible preparations of fat-soluble ingredients. Many food ingredients are fat-soluble; as a way of incorporating these in food and drink without fat manufacturers have developed stable colloidal dispersions of these materials in water, with particle sizes in the range of hundreds of nanometers. For example, the substance lycopene, which is familiar as the molecule that makes tomatoes red and which is believed to offer substantial health benefits, is marketed in this form by the German company BASF.

What is important in this discussion is clarity – definitions are important. We’ve seen discrepancies between estimates of how widespread food nanotechnology is in the marketplace now, and these discrepancies lead to unnecessary misunderstanding and distrust. Clarity about what we are talking about, and a recognition of the diversity of technologies we are talking about, can help remove this misunderstanding and give us a sound basis for the sort of dialogue we’re participating in today.

From micro to nano for medical applications

I spent yesterday at a meeting at the Institute of Mechanical Engineers, Nanotechnology in Medicine and Biotechnology, which raised the question of what is the right size for new interventions in medicine. There’s an argument that, since the basic operations of cell biology take place on the nano-scale, that’s fundamentally the right scale for intervening in biology. On the other hand, given that many current medical interventions are very macroscopic, operating on the micro-scale may already offer compelling advantages.

A talk from Glasgow University’s Jon Cooper gave some nice examples illustrating this. His title was Integrating nanosensors with lab-on-a-chip for biological sensing in health technologies, and he began with some true nanotechnology. This involved a combination of fluid handling systems for very small volumes with nanostructured surfaces, with the aim of detecting single biomolecules. This depends on a remarkable effect known as surface enhanced Raman scattering. Raman scattering is a type of spectroscopy that can detect chemical groups with what is normally rather low sensitivity. But if one illuminates metals with very sharp asperities, this hugely magnifies the light field very close to the surface, increasing sensitivity by a factor of ten million or so. Systems based on this effect, using silver nanoparticles coated so that pathogens like anthrax will stick to them, are already in commercial use. But Cooper’s group uses, not free nano-particles, but very precisely structured nanosurfaces. Using electron beam lithography his group creates silver split-ring resonators – horseshoe shapes about 160 nm across. With a very small gap one can get field enhancements of a factor of one hundred billion, and it’s this that brings single molecule detection into prospect.

On a larger scale, Cooper described systems to probe the response of single cells – his example involved using a single heart cell (a cardiomyocyte) to screen responses to potential heart drugs. This involved a pico-litre scale microchamber adjacent to an array of micron size thermocouples, which allow one to monitor the metabolism of the cell as it responds to a drug candidate. His final example was on the millimeter scale, though its sensors incorporated nanotechnology at some level. This was a wireless device incorporating an electrochemical blood sensor – the idea was that one would swallow this to screen for early signs of bowel cancer. Here’s an example where, obviously, smaller would be better, but how small does one need to go?