In early 1990 Nick Brown, the British entrepreneur behind the Paramo clothing brand, was struggling with the problem of how to make waterproof, outdoor activity clothing last longer. Sweat and condensation tends to rot conventional gear at the seams and once that happens the jacket usually has to be scrapped. As he already sold a water-repellent wax for clothing, he was particularly interested in the idea that more could be done to prolong the life of outdoor clothing using water-repellency.
He grappled with the problem for three years before turning to nature for the answer. But he didn’t have a team of physicist and biologists on hand. He had no expensive analytical equipment to help him. He finally found it with the help of a wet dog. And it cost him nothing.“Clothing”, explains Brown, “keeps you warm by trapping a layer of warm air next to the skin. But it also needs to keep you dry. So the conventional solution is to keep water out by making clothes waterproof from the outside, creating what is effectively a highly engineered plastic bag.” That’s fine as long as you don’t move. But when you are hiking or climbing or trekking through snow, the going gets hard and invariably you sweat.
“The problem is that water transmits heat 25 times more efficiently than air. So the moment you start sweating, the layer of dry air close to your body becomes moist and in the short run your clothes lose their ability to keep you warm. In the long run the seams are degraded by your sweat, “ says Brown. That doesn’t matter too much if you are running for the bus to work. But when you are camping out in the Andes, it could be fatal.
Damp dog insight
So the question he pondered was how could he design a fabric that would push moisture –(sweat and condensation) away from you, keeping you not only dry, but warm too. He chewed it over for a couple of years when one day he realised that animals share exactly the same problem. “Water off a duck’s back’ is a common enough phrase,” he says. So he started looking at sheep and dogs to see what happens to them when they get wet. “You see droplets running through their fleeces as coalescence brings it to the surface. You can actually watch it happening.”
That was his Eureka moment. “I spent a bizarre evening thinking and not sleeping and worked out that dogs stay dry and warm because their fleeces actively push water outwards.” How so? “Mammal hair is not all the same length, it is of varying lengths and that is the key,” he explains. “So on average, as you get further away from the skin, there are fewer hairs. That means the average distance between hairs increases. Thanks to natural oils, hair is water-repellent, so droplets form. Because of the laws of surface tension, droplets minimise their surface area as they get bigger by forming a sphere. To do that they have to move to where the gap between the hairs is greatest.”
Moving water by the natural physics of surface tension had to be better than trying to move water vapour by conventional means, concluded Brown. It was radically different from using breathable membranes or ‘moisture vapour transfer’ but not radically different from the way bird feathers work, he says. “Effectively mammal fleece and bird feathers works like a pump. Provided that less is coming in than going out, you’ll remain bone dry. Conventional jackets deal with 20 per cent of moisture. Our jackets can deal with 100 per cent,” he claims.
A major additional benefit is that this process works independent of humidity levels. When humidity is very high, there can be no evaporation with conventional clothing and you are basted in your own sweat. “Firemen call it boil in the bag syndrome,” says Brown cheerfully. But he says that cant happen with his system.
Brown believes that it was only by closely observing nature that he could finally came up with a product that (he thinks) is functionally superior to those of his rivals. “I now realise that very often problem solving is about using the right analogy.”
At this point the obvious question is, if this design is superior to conventional ‘breathable membrane’ products why is it not more widely adopted and why is Nick Brown not a very rich man indeed? Brown’s response reveals why much of the learning from biomimicry may be painfully slow in manifesting itself as useable products. There are often powerful market forces obstructing innovation he argues.
“We are commercially successful,” he says. “But the interest of the industry is vested in breathable membranes. And their business model is based on producing garments that have to be thrown away after a few years. Ours are designed not to become obsolete.” There needs to be a paradigm shift before his idea is more widely accepted, he argues. “I believe our system will win in the end. It took 30 years before front loading washing machines established themselves in the US even though they were technically superior to top loaders in almost every respect.”