Building the Future

Cochlear implants are electrical devices that consist of a system of tiny implantable electrodes that can directly activate "hearing nerves" in the inner ear or "cochlea" to treat deafness.

But only a restricted set of sounds can be signalled this way because the nerves are difficult to activate.

Now, University of New South Wales scientist Gary Housley and his colleagues have found that electricity from the cochlear implant can be used to make cells in the inner ear pick up short pieces of DNA coding for a gene for a nerve growth signal, called BDNF that can be injected into the ear.

This, in turn, makes the hearing nerves grow and become much more sensitive to signals from the cochlear implant, with the potential to dramatically improve the quality of the hearing experience.

Gary - The cochlea or our hearing organ converts sounds of different frequencies into information that's encoded in the auditory nerve fibres which then transmit that information to the auditory processing centres in the brain. There are about 4,000 cells called hair cells and they have these little hair-like processes on the tops of them and they respond to the vibrations produced by sound and release neurotransmitter that stimulates the auditory neurons.

Chris - And when a person goes deaf, what's gone wrong with the cochlea structure in those people?

Gary - Typically, it's the hair cells that are the most vulnerable. When the hair cells are lost, then in fact, the cells around them also seem to die. With that, they stop the production of, if you like, a hormone or a chemical that sustains the auditory nerve fibres then the auditory nerve fibre dies back. That's the state that the cochlea lies in if you like, at the point where people become severely hearing impaired and perhaps, a cochlear implant might provide a possible means of restoring a degree of hearing to those people.

Chris - When someone has a cochlear implant fitted, how does it work to restore hearing to those areas that have become hard of hearing?

Gary - A cochlear implant typically consists of 22 or fewer electrodes. What they do is by passing current from those electrodes out through the cochlea tissue, they're able to electrically stimulate and excite those auditory neurons. When those neurons fire their action potentials again, people can actually perceive sound.

Chris - So, how have you sought to improve the situation?

Gary - Well, we have tried to find the means to regenerate those auditory neurons, get the nerve fibres to a point where they're much more easily stimulated and therefore, give a broader and richer hearing experience.

Chris - How do you think you can do that?

Gary - Through gene therapy, it's possible to get cells to synthesise and release nerve maintenance factors - the neurotrophins - that have been lost when the hair cells died if you like. We use the cochlear implant to provide very short electrical pulses which were effective in actually driving the DNA into cells that were very close to the electrodes to make the nerve fibres head to those electrodes.

Chris - How do you get the DNA for the growth factor into the area in the cochlea where you want to use the electricity from the cochlear implant to get it into the adjacent cells?

Gary - We produce the DNA which codes for the sprain derived neurotrophic factor and we're able to inject that into the cochlea and then we pass the few electrical pulses and literally, within 5 seconds, we've been able to create small pores in cells that are very close to the electrodes. They take up the DNA and then in short order, they start producing the neurotrophin and within a few days, the auditory nerve fibres are growing back out and towards the electrodes.

Chris - Is this a permanent change or is this just temporary, this nerve response?

Gary - Using imaging techniques, we could see these new outgrowths for up to 3 months after our gene therapy. But by the time we'd gone out to 12 weeks, there were far fewer of these nerve fibres. So, what is clear to us at the moment is that, the expression is waning. So, this certainly would something we would want to look at and potentially find a means of sustaining the gene therapy for a longer period of time.

Chris - If you make measurements after these nerve cells have grown in this way in response to the nerve growth factor that you've expressed, does this translate into more sensitive hearing in your experiments?

Gary - Well, I think that was the really exciting point. With the regeneration that we achieved, we're able to then make a functional assessment of potential for improved hearing. The technique that we used for that is very similar to the technique that's used very broadly for newborn baby screening. It's called auditory brain stem response. We passed small currents through the cochlear implant, gradually step-up the amount of current that we're passing until, we're able to record a brainwave. With our gene therapy, we established that much smaller currents could be used to elicit a response. And then as we increase the amount of current, we got progressively greater increase in the output in those auditory centres in the brain.

This week researchers in Switzerland have created the smallest magazine cover in the world, using a tiny chisel to create an image so minute that 2,000 of them could fit on a grain of salt.

Colin Rawlings is one of the researchers behind the work...

Chris - The number one question must be, why on Earth have you done this?

Colin - Well, it sort of seemed like a fun thing to do, but also more generally, it was the work done with National Geographic, the guys that supplied the cover and they were looking for a way to sort of show kids that you could do surprising and weird things with science. So, at IBM we were pretty happy to get involved in that.

Chris - IBM has something of a rep for doing things with very small things. I remember iconically the spelling of IBM in xenon atoms about 25, 30 years ago, made lots of magazine covers then. Actually, how did you do this though? How did you actually make these tiny images?

Colin - It's actually related sort of to that work that Don Eigler did, I think that we use a very sharp tip and we start with a flat plastic layer. And then by applying or heating up the tip and then pushing it into the surface, we cause the plastic to evaporate and so we're left them with a sort of a hole in the area that we touched down on. Then if you scan over the surface making holes of the correct depth at each point, what you're left with is a sort of 3D topography of hills and valleys that if you do it correctly, it can look like a magazine cover or indeed, anything else that you want it to resemble.

Chris - So, the magazine cover is a slightly trivial application, but makes the point. Obviously, makes you very news worthy, but the point being that you could use the same technique then to make any kind of 3 dimensional microstructure, very tiny structures that you would need or have some kind of function for.

Colin - Yeah, exactly, that's right. So, as the technique gets more mature, that's sort of the processes, or sort of the way we try and go with this and there are things that you can do with 3D structures that it's hard to do with the sort of 2D structures that you can make with traditional techniques.

Chris - What sorts of things are you going to make?

Colin - So, there's now one effort that if you can focus light to a high enough degree then you can get interesting quantum effects that otherwise wouldn't be possible. So, that's something that - a paper that came out I think a year or two ago showing this theoretically and now, we try and make the experimental validation of this.

Chris - Why is this any better than what we can already do with what's dubbed "photo lithography" where we etch bits of silicon to make microchips which must be on the same sort of scale or smaller than what you are achieving here?

Colin - Yeah, exactly. In mean, the scale that we can do this on is actually a little bit better than you can do with optical lithography. Of course, where we lose its speed that it takes us much longer because we have to do it point by point. But I think the key difference is, firstly, that you can see what you've done straightaway. So, for scientists who are a bit error prone, this is a pretty nice thing that you can save for yourself a lot of time because you can directly see that you've made a mistake and then have another go. The other thing that we can do is this 3D patterning thing. That instead of writing one 2D shape that you can maybe extrude or stretch out the surface by or etch down into the surface, we can really make a 3D profile...

Chris - Can you also do this with more materials than just the traditional ways of etching microchips with silicon?

Colin - No. I think probably in the end, we're still making a shape and then we still use etching to transfer the shape from the plastic into another material or to apply metal to sort of control where metal is deposited or when dopants be controlled. So, in that sense, it works along the same lines.

It's not just the way we build houses that might change in the future, but the materials we use as well. In order to make housing across the world more environmentally friendly Michael Ramage from the University of Cambridge is trying to develop the use of bamboo to replace traditional building materials. Chris Smith wanted to know why bamboo?

Michael - We're very interested in bamboo because it is very fast growing. It's widely distributed around the world, particularly in areas where populations are growing and populations are moving to cities, but also, where trees don't grow. And it's extremely strong.

Chris - What about the environmental equation, whereby, in the same way that people in America were growing a lot of crops to make biofuels, but actually, they were taking land that could be grown for food out of production. There was an environmental cost there focused at, to buy the food in from elsewhere or turn other land into food producing land to make up for the fact that we're growing fuel crops. Can we make the same sort of arguments for bamboo?

Michael - Well, if anyone has grown bamboo in a garden, they know that it grows rapidly and it tends to grow anywhere. The countries that grow a lot of bamboo like China or Columbia, we find it grows very well on hillsides, extremely steep hillsides where you can't plant crops.

Chris - So, why are people not doing this already?

Michael - There's a long history of using bamboo in its natural form for houses in vernacular cultures. So basically, people building without architects and it's only in the last 20 or 30 years that people have processed bamboo into the type of materials we use in conventional construction.

Chris - Well, tell us more. How do you process it because when I've seen bamboo use in China, you see scaffolding or buildings to extremely great heights made of bamboo? You think, "Gosh! That doesn't look very strong" but actually, it clearly is. How is it used differently then?

Michael - So, the processing of the bamboo is, it grows around. It's a stalk. It's a blade of grass that happens to be 17 centimetres in diameter. It gets split up into slivers which are then cut down into rectangles and then the rectangles are glued together to make big sheets of what we might refer to as plywood. It's a different material, but it's like a sheet of plywood.

Chris - What's its mechanical characteristics that mean it's better or at least equivalent to what we could otherwise use?

Michael - So, it's about 5 times stronger than timber in either tension or compression, so when you pull on it or push on it. Compared to its strength, it's extremely flexible. So, its flexibility is about the same as timber.

Chris - Gosh! These are good statistics. I can't understand why we're not all doing this already.

Michael - Well, the material is - although bamboo grows all over the world and there's a lot of the material and it grows extremely fast, there isn't a lot of bamboo that's processed. It's mostly processed for flooring as you probably have seen in buildings around Cambridge. It's quite popular.

Chris - It doesn't sound like it's rocket science to make those processed bamboo materials. You chop it up and glue it together which is what we're already doing for chipboard and things anyway, aren't we?

Michael - Yes, indeed, but one of the problems is that there is at the moment, very little market because engineers and architects don't necessarily have codes they can refer to for designing bamboo buildings. Without bamboo buildings being designed, companies are reluctant to make a lot of material that doesn't have a market.

Chris - So, how does it stack up in terms of where it could be deployed? What sorts of building applications could it have and will it save people money because all of this is going to come down to the bottom line? Is this going to end up costing them a load more? If so, they're not going to do it because they're going to pass it on to the customer and become uneconomically viable?

Michael - Well, we think in the research that we're doing at Cambridge University is, looking at how we can use this structural bamboo in large scale buildings. So, 6, 7, 8, 10-story buildings. At the moment, a building like that made of structural bamboo would be much more expensive than an equivalent in steel or concrete. But we think in the long term that it will become competitive especially if we change the way we price carbon.

Chris - Will this be mainly the cladding that the bamboo is used for or would you see it being used for all of the building so you could replace the steel frame or the timber frame, or whatever sort of building you're doing with some kind of bamboo composite?

Michael - The work we're doing at the moment is looking at ways to replace the structural frame with bamboo. There is already quite a bit of material that can be used for cladding, particularly the interior surfaces.

Chris - What about lifeing of the material? We know if you build a house from an oak frame, it'll be there in 500 years if you look after it. Do we know what the lifeing of these bamboo materials is?

Michael - The same is true for bamboo. If you keep it dry and keep it out of the sun and in other words, if the architects and the engineers detail the buildings correctly and they stay dry then it will last for a very long time, just like wood will.

Chris - Why is bamboo structurally sort of ultrastructural level so good in this regard? Why does it have these characteristics?

Michael - Well, we have partners at MIT who are working on that at the moment, but in simple terms, it's made up of very, very strong fibres that go in one direction up the stalk of bamboo. Those fibres themselves are extremely strong.

Chris - And so, if you cross them so they're at 90 degrees to each other when you stick the chips together then you're going to get this very, very powerful composite in two different directions just like plywood.

Michael - Yes and there are many ways you can put them together, either crossed or all oriented in the same way to get different sorts of properties, depending what you're trying to build.

Chris - Well, I might have to build my next house out of bamboo so the pig that built his house from straw was sort of halfway there. He's still using a sort of grass, wasn't he? Michael Ramage from the University of Cambridge, thank you very much.

Arguably one of the most important considerations when designing new buildings is energy efficiency; and a lot of that relates to how many lights need to be turned on to illuminate the interior. And as we build at higher densities, and try to meet strict thermal insulation requirements, architects are having to think even more creatively about how to make the maximum use of free lighting, in the form of natural daylight. From MIT, Christoph Reinhart...

Christoph - Daylight is an important concept not only for architecture but for really, everybody. If you think back before the times when we had electric lighting in building, really daylight was a necessity the only source of us being able to see what is going on in building. Why daylighting is important nowadays, has actually two reasons. Well first of all, it tends to provide a better type of lighting than electric lighting. It's because the colours of daylighting come out more vividly.  When daylight shines on objects, you can see them better. Now, another benefit of daylighting is of course that if we have a room without a window then we have to turn on the electric light and that takes a lot of energy if we use the daylight that comes for free.

Chris - What about human physiological impact as well? Are humans better off under daylight than under artificial light?

Christoph - Yeah, it's very good that you're asking that question. So, we've known for a long time that visual rendering of objects are better with daylight because it comes in all colours of the rainbow. So, they render the colour of that object very well. Something else that's very exciting that we only found out really within the last decade is that daylight not only provides us visual information about the world around us, but it also is linked to something that's called our circadian rhythm, so our biological clock. What that concept means really is that all of us, in our brain, we have a little clock that tell us what time it is. If we wouldn't get any clues from the outside world, through light, what time it is, then we would start drifting. Some of us would have maybe 25-hour days, others would have 23-hour days. So daylight, it's very important in training us, basically keeping us all synchronised that we can all follow our lives at the same time.

Chris - But equally, is it possible to end up with too much daylight exposure if you're working in a building and care is not taken. Could you end up with over lighting of the interior?

Christoph - Well, absolutely. That can happen. So, architects and owners think, the more, the better. So, if we just open our buildings, have a fully glazed facade then we get more daylight and it's necessarily better. But that's actually not the case because once we have too much daylight and we want to read a book or do something on an electronic device such as an iPad or a computer, then we might be in situations where we can't see because there's too much light. Basically, what there is, is really too much contrast. That means if you are in a room that is partly very, very bright to sunlight and then when you look in the back of the room, it's very dark, then our eye cannot adapt, cannot take in this large range of brightness variances and that's called glare, that leads to discomfort.

Chris - So, do architects have mechanisms to predict how much light is going to penetrate into a building, what the likelihood of glare occurring is and therefore, how to mitigate it?

Christoph - There are methods in place. So, especially over the last couple of decades, we've had made in the architectural world a lot of advances in modelling buildings in a computer. So, it's as if we are putting a building into something like a computer game from the gaming industry and then we can model the light for a whole year that shines on the building. So, we have become very good at predicting how much light there is in buildings.

Chris - Equally, does the same apply when trying to get light into a building? So, formatting the interior correctly so that you can get as much light as possible as deep into your building structure as possible. So, it's not just the people who sit by the windows that are well lit.

Christoph - Yes, that's a very good question. What is very important is how high the upper edge of the window is. So, if you're in a space right now, you're looking at the window, you really want to have the distance between the floor and the upper edge of the window as high as possible. So then you can basically get away with a window that takes maybe a third or so of the whole facade, the rest is just wall. But if the window is like a band of light which is close enough to the ceiling that on the one hand it allows you to look outside, but also, it's high up. Then it penetrates light very deep into the space.

Chris - Now, we're talking here about individual buildings, but often developments occur as whole clusters of buildings. So, is there any way or any tools available for architects to be able to format whole cities even so that they make the maximum use of available light and they minimise their cooling bills, they minimise their heating bills in order to be as energy efficient and light efficient as possible?

Christoph - Legislation has been in place for a long time. Arguably, one of the first legislations in the field of access to light at the street level and then buildings comes from 1917. These were the ordinances in New York city that when all the skyscrapers were being built in Manhattan that stipulated how much offset buildings have to have from the street so that there's sufficient light both on the street level as well as on the buildings. And these were really what we would call section base. So, it's as if you draw in 2 dimension a city on a piece of paper, just the outline. You don't really think 3-dimensionally of the problem. You just see two buildings next to each other that form an urban canyon.

Nowadays, due to advances in computer rendering and just availability of data on cities, what we've been working on in our lab is an urban modelling platform called 'Umi' and what this allows is that we can effectively use data that are available for many cities which are called geographic information systems that contain information about the form, the shapes of any building in the city that usage pattern, the existence of trees around it, the value of the building and so forth. So, we can take these big databases and convert them into energy and lighting simulation programmes and scenes, run simulations of lighting and energy for whole city and then provide that back to the city. So, they can then use this information for example to have better policies of how much distance between buildings have to exist when you go away just from the daylighting and look more at energy use in buildings. We can then use this for policy measures to say, what are the most offending buildings in our neighbourhood that use too much energy? How can we help these buildings save energy for the whole city?

Shaun Fitzgerald - I think the topic of green materials for buildings is amazing because one of the challenges that we have in a building is assessing the embodied energy and how much energy or carbon was used to make materials. If you make it out of things like bamboo, it becomes a carbon sequester.