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Smart materials

16.10.2008
The country’s most elaborate travel-wear keeps the body cool in hot helicopter cabins, but transforms into a heat-retaining suit if the helicopter should fall into the sea.

We are in one of SINTEFs laboratory basins. The demonstration of the helicopter survival suit only takes a few minutes. The test person crawls out of the pool and changes into dry clothes.

Completely different rules apply during scientific trials: six hours without consuming food or drink, in a horizontal position in water at a temperature of two degrees Celsius with a strong breeze from a wind machine hitting you straight in the face. All this is necessary in order to create suitably realistic conditions.

Changes phase
The suit has been developed to help offshore platform personnel on the Norwegian continental shelf to survive should an accident occur and they fall into the churning waves below. The new suit, which has been jointly developed by SINTEF and Norwegian clothing manufacturer Helly Hansen, is tailor-made to meet the requirements of offshore platform personnel. As well as being a survival suit and providing protection against ice cold waters, the suit is customised to be comfortable during the helicopter flights to and from the platform.

“From a production perspective, people claimed that it was impossible to meet the conflicting requirements for cooling and heat insulation in the same suit,” says Research Director Randi Reinertsen, a Professor of Physiology at SINTEF and head of the working group that developed the new survival suit.

“We utilised a textile that can change phase and made use of our knowledge about how cold and heat affect the human body. This enabled us to develop a suit that works in tandem with the body’s own reactions to cooling and heating.”

In-woven capsules
The reason the newly developed Norwegian suit can manage the tasks of cooling and heating is attributed to the textile containing tiny in-woven capsules. The capsules comprise microscopic particles that consist of a specially developed type of paraffin wax. If the skin temperature of the person wearing the suit rises above 28 degrees Celsius, the wax changes phase from solid to liquid.

“Melting requires heat, which the paraffin wax takes from the body and cools the wearer in the helicopter cabin on hot days”, says Reinertsen. “On the other hand, if the person ends up in the sea, the paraffin wax changes phase and returns to a solid state, enabling the suit to return the stored heat back to the body.”

An analogy from everyday life is a glass of water containing ice cubes. Until all the ice has melted, the water retains the melting temperature of ice – in other words zero degrees Celsius. The temperature of the water will only begin to rise when all the ice has thawed.

“The findings show the textile keeps the suit wearer satisfactorily warm and comfortable for up to six hours in difficult conditions in the sea,” says Reinertsen. That can mean the difference between life and death.

Exploiting the properties
Materials have always been of great significance to humans. In earlier times, materials only had a support function. Wood, steel and iron were mostly used for building and construction. Today’s materials are of a different calibre, containing the addition of special properties, mainly electrical, optical, magnetic and chemical. Instead of using them for construction purposes, we equip them with properties that provide increased strength, better safeguarding against rust, repelling of graffiti or the ability to store or emit heat. The modern functional materials have forms such as membranes, catalysts, thin films, semiconductors and sensors.

“This is about exploiting, adjusting and adding new properties to the materials,” says Research Director Jostein Mårdalen at SINTEF. “Today we have the knowledge to develop materials in an intelligent manner with a minimum of trial and error.”

Intelligent materials
Smart materials provide us many opportunities. At the Department of Work Physiology at SINTEF, Tore Christian B. Storholmen is hard at work. He designed the helmet concept ProActive and recently received an award from the Norwegian Design Council. He displays the white helmet and explains why it is so smart.

“The helmet is lined on the inside with a material called d3o made with intelligent molecules. These flow freely as long as they are not subjected to pressure, but the second they receive a blow or impact they lock together. The material’s soft and flexible normal condition instantly locks and become hard and shock-absorbent,” says Storholmen, adding: “When the shock after the impact diminishes, the molecules unlock and become flexible again.”

The d3o material does not harden when it is subjected to impact, but the effect is comparable with a net that absorbs and distributes the force.

The helmet is shaped like a baseball cap. Parts of the helmet prototype are transparent to enable people to observe the d3o material.

The properties of d3o make it ideal for protecting the body, and it can be beneficial for sportspeople and those working in vulnerable conditions.

“I have a brother who works in the building and construction industry and he told me that many people find protective helmets uncomfortable,” says Storholmen. “I wanted to make a helmet that was good to wear and also offered the necessary protection.”

The intelligent material d3o is also used to provide knee protection in children’s overalls, snowboarders’ hats, football shin pads and protective equipment for motorcyclists.

Smart functions
“We are becoming increasingly better at exploiting material properties because our basic understanding of material properties is increasing,” says Mårdalen. “We are also gaining increasingly more advanced analytical tools to study materials at the nano-level. Possibly the most important contribution is that we can now design materials on a nanometer scale.”

Chemists and physicists have for a good many years studied materials at nano-level, but have been unable to build with sufficient precision at submicro level. Scientists have now come so far that they are in a position to construct and manipulate at atom level with sufficient precision. This is one of the main reasons why nanotechnology is now gathering speed.

“This knowledge gives us the possibility to customise materials and surfaces so they gain the properties we want,” says Mårdalen.

Improving packaging
As one example, Scientists at SINTEF utilise nanotechnology to improve the materials in food packaging. Contact with air is one of the main factors that reduce food quality. Food producers are therefore reliant on packaging that has good capacity to block out oxygen, while the recycling perspective is also important.

“Today’s food packaging has barrier solutions with up to nine layers of polymers, making it complex and expensive,” says Research Director Bjørn Steinar Tanem. “We are working to reduce the number of layers by blending nano-particles into the plastic. We are also working on solutions where we combine barriers with an increased degree of material recycling. Today the different layers of packaging comprise such different polymers they the material can’t be recycled.”

The new packaging will be better, cheaper and more environmentally friendly than today’s food packaging. The research is now in the verification phase. If this is successful, the next phase is factory trials.

Retaining heat
Can a coating really retain heat? The answer is yes. In the project Heat Reflective Coatings, SINTEF in collaboration with Hydro Aluminium and DuPont Powder Coatings, created a powder coating that reduces heat loss. The coating is applied to aluminium window and door frames.

Jostein Mårdalen brings up some of the project designs on his computer as he talks eagerly.

“The coating means that the heat loss through window frames is reduced by between 20 and 23 percent,” he says. “It is unusual to think insulation in this manner, but the effect is great. The secret behind this invention is to use nanotechnology in an established industrial process – powder coating.”

The coating’s properties may also be used for the opposite purpose: to keep heat out. One extremely relevant example may be preventing a car from becoming over heated on a warm summer’s day.

In order to achieve these properties, the research scientists have developed a coating with low heat radiation and excellent heat emission capabilities. The coating has already been commercialised and is utilised by manufacturers of aluminium frames. It is environmentally friendly, virtually free of solvents and can in time also be used to insulate other things than windows.

“From an energy perspective, this is very interesting. It’s about thinking in a revolutionary way about insulation,” says Mårdalen. “We visualise that it’s relevant to apply this coating on different types of building products to reduce heat loss or solar heating. This product is extremely useful.”

Capturing light
Some of Mårdalen’s colleagues at SINTEF are working on another coating – or thin film – that has a smart function: It will improve the efficiency of solar cells.

“Today’s solar cells capture about 15 percent of the sun’s light. The reason why more is not absorbed is that only visible sun light is captured,” says Senior Research Scientist Arne Røyset. “The conventional way of thinking is that the solar cells shall adapt themselves to the light. We have chosen to reverse the problem and also work on the sun light adapting itself to the solar cells.”

Humans can see light in the spectrum from 400 to 700 nanometres. Ordinary solar cells capture light right up to 1000 nanometres but, in spite of this, much of the light escapes. Sunlight has a specific wave length and quantity of energy. By combining two and two particles, the quantity of energy doubles, while the wave length halves.

“The thin film is placed on the outside of the solar cells and it is the optical properties that make this possible,” says Røyset. “By halving the wavelength, invisible light becomes visible and, as a result, it is captured by sun cells. We call this frequency conversion or light capture. The fact of the matter is we utilise the sun better.”

If the research scientists succeed, the coated solar cells will increase the efficiency of the solar cells without increasing the costs to any great extent. The solar cells and coating are an example of optical materials. The essential factors of optical materials are how the light is created, reflected, absorbed and spread.

“Previously material research was often about making materials stronger and lighter, as was the case with aluminium. We worked to improve the properties the materials already had,” says Røyset. “Now the research is turning increasingly more to giving the materials new functions. The potential is virtually unlimited.”

Contact: Jostein Mårdalen, SINTEF
Phone: +47 73 59 13 01, e-mail: jostein.mardalen@iku.sintef.no

Aase Dragland | alfa
Further information:
http://sintef.com

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