How to

25 August 2016

Water-Cooled Clothing Explained

Clothing designed specifically to cool you down using water is used in many industries. You might have heard of motorcyclists and race car drivers wearing these garments, but they are also used by medical professionals and their patients, military personnel during operations, industrial workers labouring in hot factories and tunnels, and animal-lovers to protect horses and dogs from heat stress.

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The most common application of this cooling technology is in the form of a vest, though it has been applied to various other items including hats, jackets, neck bands, wrist straps, wheelchair pads, dog mats, dog coats, horse blankets, and even car seat covers. It is also the basis for the cooling undergarment in NASA space suits.

Several methods have been developed to carry heat away from the body, from absorbent materials which offer relief when they are soaked in water – basically a high-tech wet towel – to full-blown piped garments which circulate cold water. There are advantages and disadvantages to each; for instance, evaporative technologies are dependent on lack of humidity in the air, and the piped cooling requires you to carry a backpack and replace the ice and battery periodically.

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California-based TechNiche International produces cooling garments which function using both piping and evaporating technology. Their HyperKewl fabric is made of ‘cellulose fibers, bi-component binders, absorbent polymer fibres and process aids, according to the product’s data sheet, and uses evaporation to take heat away from the body. Wearers need only soak the absorbent fabric in water for 2 minutes before use. It claims to provide the wearer with temperatures 10-15 °F cooler than the ambient environment for 5-10 hours, depending on humidity and airflow.

Many evaporative garments use sodium polyacrylate crystals to absorb moisture and can have a slimy, slippery feel when wet. The salt is sometimes known as ‘waterlock’ because of its properties, and is used widely in babies’ nappies, potted plants and sanitary towels. The effectiveness of cooling garments is dependent on the evaporation rate possible in a given environment.

CoolPax are frozen and put into pockets to cool the body by taking heat away as it melts slowly. These are made of a phase-change material which is capable of storing and releasing large amounts of energy when it changes state between liquid and solid. The temperature of these CoolPax stays constant until all the material has melted, which makes it useful for cooling.

However, the effectiveness of the mechanism decreases over time, as the transfer of heat between the frozen core and melted outer layer slows down cooling. Also the products can be heavy, making any physical labour more difficult, as the chemicals most commonly used have only half the latent heat of fusion of ice, so you need twice the mass to get the same effects.

Their KewlFlow products pipe water cooled by an ice pack around a garment, and come with static and portable coolers. These can be very effective in any environment and provide consistent cooling for long periods of time, only limited by whether or not you change the ice and battery when needed. However, they can be a bit unwieldy and are pretty expensive.

TechNiche boasts high-profile clients such as Harley Davidson, BMV, Adidas, Tough Mudder, Medecins Sans Frontiers, KNVB, London’s 2012 Olympics, KTM Racing, and Pet Planet.

Enter VTT Technical Research Centre of Finland. These researchers specialise in Microfluidics, which is pretty much exactly what it sounds like: the study of how liquids move and behave in very, very, very tiny quantities. We’re talking channels with diameters of around 100 nanometres to several hundred micrometres. 

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This area of research emerged in the 1980s and has applications in all sorts of fields, like molecular biology and cellular physics. It’s been used to design many things that are used widely, such as printer cartridges, and a range of ‘labs-on-a-chip’, which can analyse substances like blood and water, and use sensors to detect, say, a bacterium that contaminates water.

VTT are at the forefront of microfluidic research, and are finding new ways to manufacture products that are commercially viable.

Ralph Liedert, the Key Product Manager of VTT’s diagnostic platforms came up with the idea to develop a cooling garment that uses microscopic channels and connects to a smartphone app to control your temperature. He was struck by the idea as he queued at Disneyland on a sweltering day with his daughter, wishing there was an app that would cool him down.

Unfortunately for parents in hot queues everywhere, the technology is not quite there yet, though VTT are working on making it a reality. They made a major breakthrough in November 2015 with a large-scale production method for embossing channel structures onto big sheets of plastic film, and are now looking for partners in the sports, wearable technology and cosmetics industries to commercialise the idea. The hot embossing method is cheaper and faster than the conventional ways used to manufacture computer chips and labs-on-chips, like photolithography.

Liedert explains the thought process:

‘Minuscule microfluidic channels can be compared to the cardiovascular system[…] This gave us the idea for other applications of our new method in addition to diagnostics, such as heating or cooling channels for clothing, or the storage and transport of substances that are only needed in small volumes (perfumes and fragrances) or that are very expensive (medicine).’

The channels can be embossed on hard and soft plastics, meaning the technology has a range of applications. Some ideas include creating credit card-sized perfume dispensers, cards to measure precise doses of medicine, and even gadgets to serve tiny quantities of hot spices in restaurants.

There are hopes that the tech could be used to warm up as well as cool down, which could make a big difference in Finland, where temperatures can fall to a wintry -50 °C!

Naomi Pyburn

Naomi is an English graduate with an itch to write. Her free time is spent blogging, reading feminist writing, cycling, cooking and managing her food Instagram account. Her not-so secret talent is the ability to nap anywhere.