You are as old as the theory you believe in!
06 December 2018 by David Bott
This week started a little early, for I flew out to Boston on Saturday for the 2008 Fall Materials Research Society Meeting. I am not sure how long I have been going to this meeting, but it must be close to 25 years. It has about 40 parallel sessions and covers nearly all of materials science. It provides a useful way to get primers in new areas and catch up with the latest thinking in others.
On Monday, the first presentation was on Multiple Exciton Generation. As I understood it, normal photovoltaic cells are limited to an efficiency of about 32% because any incident photon with an energy greater than the band gap will lose the excess energy as heat (being a physicist, the presenter said “thermal phonons”). The idea is to use colloidal nanocrystals of semiconductor to collect photons with multiples of the band gap energy faster than they can thermalise and so increase the energy efficiency of the cell. I think they proved that it was possible to do the basic science but left the issue of how they would harvest the resulting excitons for others to ponder. Theoretically they have increased the efficiency to 42%.
Next up was a chemist who delighted in showing picture of chicken wire – a.k.a. conjugated aromatic chemical structures. These have been used for years to build conjugated (and therefore optically and electrically active) chains and sheets, but this guy reckons that he has made 3 dimensional conjugated structures.
Next up was one of Tony Ryan’s ex-students (he may even have been paid for by ICI). He makes polymersomes using block copolymers. In these the molecular architecture of the copolymers is adjusted to form vesicles of defined size. They are often touted as drug delivery systems and the design here was particularly neat. The size of the polymersome was at a level that it could be absorbed by a cell using invaginative endocytosis. Once inside a cell, particles are usually further processed by lowering the pH. This would disrupt the structure of the polymersome, delivery its cargo into the cell. A further build was that the cargo altered the osmotic pressure and disrupted the cell. Neat work, and supported by well presented characterisation data.
The next presentation, actually in a session half a conference centre away, demonstrated the power of fashion, for it used RNA attached to gold nanoparticles designed to be absorbed into cells by endocytosis. In this case the “treatment” was biological – using the RNA to affect the cell growth – but it does demonstrate that the use of nanoparticles in biological systems is getting more adventurous and better defined.
The next presentation, even further away, used viruses as templates for the growth of nerve cells. There is a fair amount of work aimed at finding ways to re-grow nerve cells, mainly because they don’t - which means nerve damage is invariably catastrophic. What seems to be evolving is an understanding of the type of substrate needed to promote nerve growth – highly linear polypeptides of specific sequences, but entry and exit substrates need to be different.
The final talk of the morning was a review of collagen. Collagen is the basic building block of connective tissue and, despite many years of investigative work, seems to forever yield new insights. The presenter managed to wring a new slant on the question by asking how a single polypeptide could have become so dominant in biological structures, but then failed to answer his own question.
One of the joys of the MRS is the Symposium X lectures. These take place at lunchtime and provide free pizza, thus guaranteeing a large audience. They are invariable introductory and usually populist. Mondays was by a physics professor from the University of Texas at Dallas and was based on her book “The Physics of NASCAR”. It was a well-constructed run through the physics and materials science of the cars construction, its energy absorbing bits, the engine, fuel and oil – all highly limited by regulation. Her final point was the kicker. Apparently, the circulation of all the “scientific and technological magazines” is about 18 million and the readership is 80% male with an average age of 47. 75 million people follow NASCAR, are about 60% male, has an average age of 26 and want to know why “their” driver didn’t win each weekend. Public engagement in science and technology should address what people want to know rather than preaching. Well done, Diandra!!
After lunch, it was trip down memory lane to see an old friend talk about the synthesis of novel electroactive polymers for cheap, reasonable efficiency solar cells. I talked to him afterwards and he is getting pots of money from the Victoria Government to develop the science and technology.
I stayed on for a couple more talks in the same vein, but they were less convincing!!
The next morning, I again went back – but this time to physics side of the coin. First up was the Nobel Prize winning physicist that all my friends hate. He is getting on now, but his enthusiasm for whatever he has just understood never fails to impress. This time, he has discovered spinodal decomposition and the gyroid phase. I think I first heard this described about 25 years ago, and is difficult to achieve – each of the 2 phases are co-continuous and permeate the whole space. The reason Alan is interested is that it gives a very large surface area between the 2 phases and is thus well set up for high efficiency ”bulk heterojunction” photovoltaic cells based on conducting polymers. His joy at the titled electron diffraction experiments he described
were either touching or a contrived practice for a funding application – who can tell.
He was followed by another man who has been doing roughly the same thing for the last 25 years. He concentrated on the surface states in bulk heterojunctions and tried to disagree with Heeger, but the only supportive response he got was when he showed a picture of snow-covered Chicago as an answer to Heegers omnipresent picture of sunny Santa Barbara. You should never criticise a god (even a minor one) in his temple.
Since I had been spotted by Richard Friend, we took time out from the next few talks to catch up. He was unimpressed by Heeger’s work, worried that the current research councils imperative was more on the side of quality of life and less on “making money” and generally unhappy that so many unimaginative academics were filling up the system without adding to the understanding of his fields. He has just finished his stint as Dean of Science (or whatever) at Cambridge and has a 2 year sabbatical as a result. He is intending to start a new company based on cheap, moderately efficient photovoltaics. We should watch him, the last 2 he started were doozies!!
I went back to catch his talk, the first of half he had mildly re-written to undermine Heeger. Don’t you love academics? He then went on to describe a series of time resolved spectroscopic studies of the excitons in organic photovoltaics, where pico-second generation, low mobility and nano-second recombination mean that the efficiency is decreased – but that the application of a bias voltage separates the components of the exciton and allows higher efficiency. He was followed by another synthetic paper of indeterminate importance.
Tuesday’s Symposium X was by a retired Army Colonel who has been running DARPAs medical programme for a while. Given that the audience of 400 was eating pizza, the early pictures of burned and mutilated soldiers were attention grabbing. Statistical analysis of Vietnam had apparently proved that the “golden hour” is a myth and you have about 20 minutes tops before you are beyond help, so he repeated the H2S experiments on chemically induced hibernation that Tony Teather had described at the RAEng a few weeks ago. He then went on to describe other urgent ways of dealing with flash burns, multiple penetration injuries and head trauma. His oft-repeated assertion that this benefits civilian healthcare didn’t quite ring true – we don’t tend to get massive and simultaneous injuries of type described in everyday life. Most civilians suffer from chronic rather than acute problems, but he’s going to spend the money anyway so he might as well try for relevance!! After the shock-horror bits, the section on prosthetics was mild and more interesting – the latest systems which are driven by thoughts require an interesting combination of physiology, materials science, electronics and software. The section on regenerative medicine built on some of the talks I had seen the day before (all probably funded by DARPA) and he ended with the challenge of fast tissue regrowth.
I thought I ought to check out his assertions, so covered the “tissue scaffold” session that afternoon. First up was from the Langer group (famous for growing the scaffold for an ear on the back of a mouse). There are many ways to get 2 dimensional templates and replicate them into almost any material, but 3-D stuff is difficult. As I understood this paper, they use a photo-polymerisable monomer and a 3-D interference pattern produced by a laser to get a porous scaffold on a bug friendly polymer. Not sure it was worth an invited talk!!
Next up was an electro-spinning paper. This got to be trendy about 7 years ago, but can trace its roots back to a 1902 patent and (allegedly experiments in the 16th century!). A polymer solution is slowly pulled out of a needle at a high differential voltage from the target – usually a rotational mandrel or sheet (or my hand!). They used the standard biocompatible polymers and got the standard amorphous networks that turned out to be good for cell growth. What a surprise!!
Next up was an advertorial for the Keck Centre for 3-D Innovation at the University of Texas at El Paso. They have assembled the whole range of additive layer manufacturing equipment (like the Loughborough Rapid Manufacturing Centre would be if it had a large cheque book) and were using it as a bespoke manufacturing set up for local biomaterials companies. What was depressing was that the guy didn’t seem to know what they did wit the materials he made for them!!
Next up was a guy spinning regenerated silk using microfluidics. This is reasonable similar to the core technology of Oxford Biomaterials (nee Spinox) but missed out on the fundamental insight into the actual spider “technology”. Okay, so I ought to declare an interest, but it was uninspiring work!!
The last paper of the day was an intriguing one entitled “earthworm inspired locomotion”. Given by a guy from Cornell, it used a thermo-reversible polymer gel inside a glass tube. Staring with the swollen gel, he heated the plug from one end, it contracted away from the tube walls and towards the constrained end. As the heating progressed down the plug, it ended up in a contracted state with its centre moved down the tube by a couple of centimetres. Cooling from the same end, meant that the polymer expanded to anchor it to the tube and then expanded along its length and the cooling moved down the tube. Quite the best movie I have seen in a while. I cannot yet think of a use for this, but there has to be one – it’s so cool.
The next day started with a paper on fast optical control of spin states in quantum dots. Even with Nick Appleyard coaching me over the e-mail, I was lost and confused – and this was the graduate student because the professor was delayed by weather!!
Back into more comfortable territory for a paper on aortic ageing by a man with a truly impressive beard. It turns out that the aorta has an inside layer of collagen, a middle layer of elastin mixed with a little collagen and an outer layer of about 50:50 elastin and collagen. The average aorta apparently beats several billion time sin our lifetime so the mechanical properties and fatigue resistance are of real interest to an ageing human being. The upshot of the various analytical techniques used is that the elastin loses its crosslinks over time (making it less elastic) and the collagen crosslinks more (this is why old meat is tougher than meat from young animals, but don’t tell my wife!). Since these processes are protein mediated, it does offer the hope that tissue ageing can be reversed – but then who wants a heart that last forever if your brain is mush?
This was followed by an eternal favourite at the MRS – the talk on mussel fibres. It was biomimetics that brought me to Boston 25 years ago, so I have now seen several generations of this talk. I guess the novelty was that the speaker was from university in Indiana, which is nowhere near the sea!! He did have a better peptide analysis of the adhesive that showed the presence of DOPA
Couldn’t resist one chemical formula!! Those hydroxyl groups probably explain the strong binding and reactivity in seashell adhesives!
I then went to my final Symposium X. With the rather arch title “Materials Science in Profitable Solutions to Oil, Climate and Proliferation” I was prepared for the worst, and the bio of the speaker did nothing to assuage my worries. When a guy who looked like the spitting image of one of the detectives from Tintin peaked out from the podium, my joy was complete. However, I was wrong. Amory Lovins may come across as being a long way up his own posterior, but he has a right to some pride. His talk started with a scary facts overview of the world (well, actually it was only America, but he does come from Snowmass, Colorado) and went on to clearly unpack the challenges, detail some of the solutions and explain the needs. That he built his own low impact house in 1983 gives some clue to why I like him. I will chase down his detailed writing and analyse them properly but even if he is 80% wrong, the 20% has been well though through and I was impressed.
The flight back was not nice – I am too old for cost saving cheap seats and will sue Cyrus for the debilitation so caused.
Thursday was spent catching up with e-mails and the machinations of the LCV and Agri-Food IPs.
Friday I made the trek down to Swindon. First up was a visit by a horde of STFCers. It was too big and we struggled to get away from crop-dusting and into clear air. I think their basic message was that they wanted to be our friends and help us spend our money more effectively and they were our natural RC partners. The bit when they said they found it difficult to apply for our money was a dead giveaway. I don’t know if anyone else was impressed?
The final act of the week was 2 hour phone call with Mark Williamson (Carbon Trust) and Andrew Haslett (ETI) to prepare the document that Tom Delay, David Clark and Iain (allegedly) promised the ERP for the new year. I had to correct the usual misunderstandings about what we do and how we do it, but then so did they, so we are getting better at mutual understanding. Andrew seems to be going for a complete engineers model of the UK energy system so that ETI can invest appropriately. I cannot help feeling that since many have been at this for years, his solo efforts won’t cause anything more that a delay in TI action, but then what do I know?