Gore-Tex

This unassuming looking material is a surprisingly high-performance fabric. Gore-Tex is the trade name for this porous polytetrafluoroethylene (PTFE) fabric membrane whose chemical inertia and biocompatibility mean that it is used to mimic the stomach wall in hernia operations and to replace veins in vascular grafts – in aortic bypasses, for example. However Gore-Tex is probably most well-known for its ability to protect us from the elements in breathable rainwear.

By rapidly stretching PTFE under the right conditions you can create a very strong, durable, and waterproof microporous material that interacts in an interesting way with water in its various states. The surface of the PTFE membrane is pitted with over 9 billion microscopic pores per square inch, and these pores are approximately 20,000 times smaller than a drop of water, but 700 times bigger than a molecule of moisture vapour. Water droplets can’t penetrate Gore-Tex but moisture vapour – sweat, for example – can easily escape.

These qualities of chemical inertia, biocompatibility and microporosity also make this material useful as a bandage. This sample came from a cycle shop where it was sold as a gauze to dress cycling injuries: while protecting the wound from rain, dirt and contaminating substances, it still allows it to ‘breathe'.