How long does a piece of clothing last you before you have to throw it away and get a new one?
Clothing designers are beginning to use a technology from all sorts of applications, from mechanical engineering to buildings, to improve the lifetimes of clothing. In small electrical components and large buildings alike, fractures and cracks can be catastrophic. In many cases, it is simply too hard to detect all of these problems, so scientists make the problems solve themselves! Using materials which can self-heal – that is, repair themselves with no external influence – can make designs last much longer and prevent many disasters.
Self-healing fabrics provide a way for clothing to become more durable, and increasingly offer more innovative functions. When a piece of clothing made from one of these fabrics is damaged or even cut in half it can ‘self-heal’, making it much more durable. There are many types of self-healing fabrics. Commonly, the material is made of polymers which can be repaired using an adhesive, which is either pumped to the break through a system of tubes, or stored inside microcapsules distributed around the material, which split open as the material breaks.
Last week scientists developed a material which can self-heal and protect the wearer from dangerous chemicals. The materials were made by coating an ordinary material with a series of liquids to create layers of polyelectrolyte coating (positively and negatively charged polymers), in this case like the polymers in the proteins that comprise squid ring teeth. Each coating is less than a micron thick, so barely affects the look of the garment, and could even be applied to the stands of fibre before the material is made.
The scientists found that they could add an enzyme between these layers. They added urease, an enzyme which breaks urea into ammonia and carbon dioxide, and showed that adding the enzyme would work to stop the urea from reaching the skin of the wearer. By extension, any number of chemicals could be broken down by adding different enzymes, from the organophosphates present in herbicides and insecticides used in farming to hazardous chemicals used in factories and in chemical warfare to harm soldiers, to stop the chemicals from reaching and harming the skin.
Materials are also being created which, when broken, can restore their electrical properties. This is critical for safety, because damage to the material may change its resistivity and thermal conductivity, causing overheating. Scientists have added a dielectric insulating factor, nanosheets of two-dimensional boron nitride, which is added to a plastic polymer base. The electrostatic attractions present draw the broken pieces back together so that the hydrogen bonds can be re-established, and the mechanical, thermal and electrical properties restored.
For now, the developments are limited to industry, such as in farming and factory work, and the teams are still looking for ways to make more conventional textiles self-healing. But who knows how soon you’ll be able to find all this, and more, in your wardrobe!
David Gaddes, Huihun Jung, Abdon Pena-Francesch, Genevieve Dion, Srinivas Tadigadapa, Walter J. Dressick, Melik C Demirel, Self-healing Textile : Enzyme Encapsulated Layer-by-layer Structure Proteins, 2016, ACS Applied Materials & Interfaces, 10.1021/acsami.6b05232 (accessed 31/07/2016)
Penn State, Self-healing textiles not only repair themselves, but can neutralize chemicals, 25th July 2016, ScienceDaily, www.sciencedaily.com/releases/2016/07/160725121850.htm (accessed 31/07/2016)
Tanya Trofimencoff, Breakthrough in Self-Healing Electronics, 26th July 2016, Engineering.com, http://www.engineering.com/ElectronicsDesign/ElectronicsDesignArticles/ArticleID/12727/Breakthrough-in-Self-Healing-Electronics.aspx (accessed 01/08/2016)
Chris Woodford, Self-healing Materials, 15th March 2016, ExplainThatStuff!, http://www.explainthatstuff.com/self-healing-materials.html (accessed 01/08/2016)