Alex Goldmark investigates how new, responsive materials are changing the urban landscape.
The next breakthrough in architecture may not come from the likes of Frank Gehry, whose designs – from the Guggenheim in Bilbao to the Walt Disney Concert Hall – draw tourists from across the world. It’s more likely to come from a chemist. Why? Because our future buildings will be shaped as much by the materials on offer as by the visionaries whose work we come to hate or love.
Scientists are developing new compounds that aren’t just stronger, cheaper or cleaner than their predecessors, but are also smarter. They interact with the world around them, responding and adapting to it. They react to stimuli such as heat or light, stress or moisture – even to pollution.
“The benefits of a built environment that does some of the thinking for us shouldn’t be underestimated”
The potential benefits are impressive. Some of these so-called ‘smart materials’ reduce a building’s energy consumption by maintaining stable temperatures without the need for air conditioning. Others have resilience built-in, actively mending wear and tear. Still others can change the world around them. From self-repairing bridges to air-filtering paint, here’s a look at the technologies likely to transform the spaces in which we live.
The simplest innovations are already on the market. These aren’t the building blocks themselves, but the final layers we put on them. Several companies, including Johnstone’s in the UK and Sto® in the US, are offering external wall paints that clean themselves, thanks to a structure that repels dirt, inspired by the humble lotus plant. The rough surfaces of its leaves, whose cells are arranged in extensive folds with tiny wax crystals jutting out, cause water droplets to form little balls which attract dirt particles as they roll to the ground, nudged along by microscopic pockets of air. This new generation of paints draws on the same principles, so that the slightest shower washes away any build-up of dust and dirt. It doesn’t just make for a brighter, more attractive building: it also cuts maintenance costs, and reduces chemical runoff from cleaning products.
Other paints go a step further: purifying the air around them. It’s a technology well suited to the Philippines’ capital, Manila – the world’s most densely populated city, where high nitrogen oxide (NOx) levels result in more than 4,000 premature deaths a year. In 2010, the Metro Manila Development Authority teamed up with WWF-Philippines, the Global Campaign for Climate Action and paint company Boysen to create a 200 square metre mural at a metrorail station.
Artists covered this vast surface with Boysen KNOxOUT, a paint made with ultrafine titanium dioxide. This acts as a photocatalyst, harnessing energy from light to break down NOx in the air as it meets the painted surface, giving off negligible amounts of water, carbon dioxide and calcium nitrate. Tests carried out by the Philippine Institute of Pure and Applied Chemistry suggested the mural can reduce pollutants equivalent to those emitted by 30,000 vehicles a day. The mural doubled up as an anti-pollution campaign, overlooking the city’s busiest highway and poignantly facing the Marikina River which burst its banks in 2009, flooding the city with dirty water and displacing almost half a million people.
Wear and repair
Keeping clean is one thing; keeping healthy another. What if our built environment could have the same resilience as our bones?
“Throughout your life”, explains Janine Benyus, Head of the Biomimicry Guild, “your bones form and reform to reinforce lines of stress.” She envisions structures that mimic this by responding to the stress of frequent use.
It’s a vision which might soon materialise, thanks to research into innovations in structural concrete led by Carolyn Dry, Emeritus Professor of Architecture at the University of Illinois. “Concrete is brittle”, Dry explains, and so “the usual repairs do not hold.” She has developed an adhesive repair material, which can be embedded in similarly brittle, hollow fibres in the concrete. These crack when they come under strain, releasing the adhesive which penetrates the fissures and sets to form a new bond. It’s an automatic infusion of structural integrity, cutting repair costs and increasing safety.
Of course, prevention is better than a cure, and this is where Dry sees the real benefits of her invention, which she has tested on four full-size model bridges. The ones embedded with self-repair fibres performed better than the control bridge. “The entire structure [was transformed] into a ductile material,” she explains, with “energy … dissipated all over.” The result was not only the prevention of catastrophic failure, due to the enlargement of any one crack, but greater resilience overall, thanks to the fibres’ ability to dampen down vibrations.
It’s something that should be particularly attractive to US government bodies, which are facing an estimated $2.2 trillion bill for infrastructure repairs over the next five years, according to the American Society of Civil Engineers. But although Dry’s self-repair concrete product is ready to sell, there haven’t yet been any takers. Construction firms in the US, her current target market, are incentivised to use cheaper conventional concrete and rebuild roads more frequently, she explains. However, she hopes that plans by the US Department of Transportation to enforce lifecycle budgeting will mark the beginning of a shift to longer life materials.
Funds are already forthcoming for another application of Dry’s work, though: self-repair aircraft. The US Air Force Small Business Innovative Research programme is supporting the development of self-repair fibreglass and graphite laminates. Dry believes that the weight of planes (and therefore, their fuel consumption) could be reduced by using materials that are thinner, yet more resistant to stress. And she sees huge potential for further applications, from offshore pipelines that can remain intact under extreme pressure at the ocean floor, to boats that can heal dangerous ruptures quickly enough to stay afloat.
Professor Pradeep Rohatgi, Director of the University of Wisconsin-Milwaukee Composite Center, is working towards similar goals – but with a different approach. His focus is on metal matrix composites (MMCs), an industry already worth $100 million a year. MMCs are made by combining a metal with a different class of material, resulting in new properties and behaviours. Rohatgi is working on a new form of metal which, he claims, could withstand the intense heat of a bomb blast, or the impact of a car crash. Like Dry, he wants to keep the strength of the material, but make it less brittle.
He is creating a foam-like metallic structure, with little hollow pockets – micro-balloons, he calls them. “The cells are smaller and more regular than air bubbles, which make them better at energy absorption”, he explains. “They are also very light.” These micro-balloons are filled with a secondary material, such as fly ash – a by-product of coal-burning power plants. This recycled dust behaves like Dry’s adhesives, leaking out to fill cracks and breaks when stress, impact or heat causes the balloons to burst. Rohatgi is looking for ways to take his new metals into production, with funding for the next stages of his research from General Motors and Ford.
Black roofs trap heat. White roofs repel it. A difficult choice in an unstable climate, but one that architects may no longer have to make. New roof tiles can modify their surface to be dark or light, responding to the temperature outdoors. Former MIT researcher Robbie Barbero has co-founded Thermeleon to commercialise a coating for roof tiles that changes its properties to keep the building warm or cool, “with no input or thought required from the building owner”, he says.
So how does it work? The coating contains a polymer which dissolves in gel when temperatures drop, revealing a black background which absorbs light. The process is reversible, and so as the temperature rises, the polymer separates itself from the gel to form a white mixture that reflects light. Barbero expects a commercial product to be ready next year, and says he has investors lined up.
Roofs are a good starting point for improvements in energy efficiency, but office workers are perhaps more likely to notice and appreciate smart windows. Several universities in the US and China are working on thermochromic windows which, like Barbero’s roof tiles, respond to outdoor temperatures. The most common method uses a vanadium oxide (VO2) film coating. The properties of VO2 change dramatically in response to heat, increasing its opacity and reflectivity. Yes, the increased opacity may dim the view – but this could be useful in contexts where blinds themselves are too clunky or costly to operate.
The benefits of a built environment that does some of the thinking and facility management for us shouldn’t be underestimated. As the climate shifts, the task of predicting and preparing for volatile conditions isn’t getting any easier. Our ability to master the logistics of a quick response to a sudden shift (a natural disaster, for instance) is, at best, unreliable. Building a new landscape that will respond instantly for us could save billions in repair and rehabilitation costs. The technology is there: the question is whether today’s investors can respond soon enough.
Alex Goldmark is Contributing Editor at GOOD.
Photos: ©/PBAI / EDSA