Pinecone-Inspired "Smart" Clothes Expand, Contract

James Owen in London
for National Geographic News

October 13, 2004

We're accustomed to borrowing from animals and plants when it comes to
clothing ourselves. Wool, cashmere, cotton, and the like all help to
keep out the cold.

But what about clothing that keeps us from overheating? Short of stripping, this isn't such an easy problem to solve.

Yet scientists may have done just that. Again, their inspiration comes from nature, but not from sheep or cotton plants. Actually, it grows on evergreen trees.

Britain-based researchers are now creating a new fabric that they claim adjusts automatically to changing body temperatures to keep the wearer cool. Its design is based on the mechanism used by pine cones to shed their seeds. This so-called smart clothing is being developed in England at the University of Bath's Centre for Biomimetics.

The department's head, Julian Vincent, said, "We've all known days when the weather alters quickly and it's difficult to dress to match the changing temperature. The new smart clothing will make all that unnecessary."

Biomimetics is the concept of taking ideas fine-tuned by nature over millions of years and mimicking them to develop cutting edge designs and products. This isn't a new discipline—in the 15th century Leonardo da Vinci designed flying machines based on his studies of birds. But recently biomimetics has become the focus of increased scientific investigation.

Work on the new smart fabric first began after an approach from the U.K. government. Military chiefs were seeking a more efficient field-clothing system for Britain's armed forces.

Vincent said, "When you get hot you produce perspiration, and we wanted something to get rid of the sweat. So we looked around in the plant world for mechanisms where a change in humidity causes a change in shape. Actually, there are quite a lot of them, such as peapods, which go bang when they dry out. But the pinecone turned out to be the best model."

Cone Scales

Pinecones remain closed while growing on trees, but after they drop they gradually open, allowing their seeds to be released. They can do this because the cone's scales have two layers of stiff fibers that run in different directions.

The inside of the scale expands more than the outside as the cone dries out. This causes the scale to bend outward.

When the idea was applied to the new fabric, this mechanism was reversed. "It's very simple," Vincent said. "You cut flaps in the clothing, and as the fabric absorbs water, one surface swells up and the flaps bend backwards."

The clothing is covered in these tiny flaps—each one just 1/200 of a millimeter (1/5000 of an inch) wide. When the wearer gets too hot, the flaps open automatically, so outside air can get through and cool them down. As the body's temperature drops, the flaps close again.

"It's the material itself which is responding, so it's only in the areas where you're a bit hot and sweaty that it's going to open up," Vincent said.

A waterproof second layer prevents any rain or moisture getting through to the skin.

Vincent was cagey when asked about the materials used in creating the heat-sensitive fabric. "All sorts of different plastics and polymers are available—it's a matter of choosing the right ones," he said.

Vincent says the new material could have a wide range of applications, from outdoor gear to dresses, hats, and dress shirts. He says the technology could be in everyday use within a few years.

London College of Fashion is the other major partner in the project. Ph.D. student Veronika Kapsali has been working on the prototype material for the past three years.

"It's going to lead to a fundamental change in clothing," Kapsali predicted. "It's up to me to make something that looks pretty cool as well as innovative. I see this as a fascinating interface between design and technology."

Social Function

Besides preventing damp patches under the arms, Vincent reckons the fabric could have some interesting social functions.

"Having clothing that changes its shape when it gets humid could be quite fun and is almost a fashion statement," he said.

He says it may also have a role to play in the dating game—by signaling interest to the opposite sex.

"When you meet someone you find attractive, you quite often get a bit heated, so the fact your clothes are getting a curly surface is a bit of a giveaway," he said. "What you could then do is have the inner layer a different color from the outer layer, so as you start getting interested your clothing changes color."

This isn't the first hi-tech garment to be inspired by a design found in nature. Swimsuits like the one worn by multiple gold medal winner Michael Phelps at the recent Athens Olympics mimic hydrodynamic ridges on a shark's skin and reduce a swimmer's drag in water.

Vincent and his colleagues at the University of Bath are also investigating the structure of penguin feathers with the goal of developing thinner, more efficient insulation fabrics.

"A penguin pelt has got a temperature gradient in the order of 80 degrees Centigrade [176 degrees Fahrenheit] across a thickness that's no more than two centimeters [0.8 inch]," he said.

Meantime, if someone of the opposite sex looks your way and their clothes start switching color like a chameleon, they're probably at the cutting edge of fashion. It's also possible they would like to get to know you better.

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