Wearable technology may make you think of trousers with in-built mobile phone chargers, or a travel jacket complete with an in-built neck pillow and dedicated headphones pocket – but the materials we make many items of clothing out of today are technology in themselves.
Clothing made out of bendable batteries and flexible fabric circuits are coming, but man-made materials that wick moisture away from the skin to keep you comfortable are already here.
The most well known synthetic material that is used in sportswear, adventurewear, and workwear, is expanded polytetrafluoroethylene (ePTFE), better known as Gore-Tex.
Gore-Tex was the result of somewhat of a ‘happy accident’ in 1969 by Wilbert L. Gore and his son, Robert W. Gore, when they applied a sudden tug of pressure to polytetrafluoroethylene (also known as PTFE or “Teflon”), stretching the material by 800% and creating a micro porous structure that was about 70% air with 1.4 billion pores per square centimetre.
Until the invention of Gore-Tex, most clothing was made from natural fibres such as cotton, wool, silk, or hemp. Nylon was developed in 1935, but it was not until after the Second World War that it was used to make clothing due to shortages of silk and other materials, and it does not make a great clothing fabric as it traps water against the skin.
In contrast, Gore-Tex is a hydrophobic and breathable fabric. The micro-pores are large enough to allow steam produced when the body sweats to slip out, but on the outside the difference in surface energy between water and the PTFE creates a surface tension that causes water to bead-up into larger droplets that cannot get through. Clever! This surface energy is then maintained with a durable water repellent (DWR) finish on the surface.
Most people know Gore-Tex from its use in clothing and footwear from brands like Engelbert-Strauss, but the porous nature of the material also makes it ideal for a variety of other applications, most interestingly in grafts within the human body. The material is nearly entire inert, and the micro-pores allows the body to grow through it, which means you can find in a variety of products ranging from sutures, to vascular grafts, and synthetic knee ligaments.