The development of flexible, stretchable electronic components means that electronics can now be integrated directly into clothing. The next step towards smart clothing will be smart fibres, turning the garment itself into wearable technology.
For wearables to reach a truly mass market, they will need to be useful, practical, smart and stylish. Seamless integration into fabrics and clothing is merely a logical extension of wearable electronics. This means sensors are always located close to the body, making the devices more comfortable and less intrusive. Owners are able to use their wearables frequently and regularly, so enhancing the quality of the data collected. According to market analyst IDTechEx, 2015 was a record year for investment in smart clothing and e-textiles, with market volumes reaching 100 million dollars. The market is already forecast to be worth 3 billion dollars in 2016.
The term “smart clothing” actually covers a wide variety of different technologies: based on physical and chemical changes on their surface, textile fabrics can integrate functions such as lighting, heating, controlled release of substances, temporary changes in colour or texture, as well as sensory and actuating properties. Examples already in existence include jackets for drivers of convertibles with built-in heating and sports clothing which detects when the wearer is getting too warm and opens vents by way of shape memory alloys.
The integration of electronics and microsystem technology into textile fabrics enables a range of additional functions to be implemented for various applications. Chip manufacturers have developed special System-on-Chip (SoC) solutions for the wearables market. The Curie module from Intel, for example, is the size of a button and incorporates a microprocessor, Bluetooth Low Energy Radio, sensors, as well as a battery charger.
Iron-on LEDs
Fashion designers have long been experimenting with light sources built into clothing. Miniaturised, energy-efficient LEDs are ideal for creating lighting effects in flexible, light, shapeable fabrics. Some examples of this “light-emitting fashion” were presented in the fashion show held as part of the 2015 Maker Faire Berlin: Guido Burger, for example, sent a model down the catwalk wearing a so-called “social skirt”. The key feature being that the skirt has large numbers of motion sensors worked into it which detect an approaching smartphone and then alter their lighting behaviour. Light designer Lina Wassong made a virtue out of a necessity: she, too, was looking to sew lots of multi-coloured LEDs into a dress, but was frustrated by the available technology. So, together with friends, she set about designing a flat LED that can be simply stuck or ironed onto the garment. Using an Arduino – an open-source microcontroller board – she is able to control lots of the tiny lights individually, making her dress a real eye-catcher at any party.
Printed-on photovoltaic energy
Generating power from the electronics integrated into clothing is of more practical benefit – to power a smartphone or other wearable tech, for example. That is what designer Theresa Scholl did with her “Pink Bionic” textile product. Scholl is a masters student in Textile Products at the Hochschule Niederrhein college. Her smart-fabric top features a pattern made of imprinted conductor strips which converts sunlight into power. A delicate steel net relays the electric current to a storage unit.
Flexible display
Another key step in creating smart clothing is the ability to integrate a display into the fabric, using which the user can interact with the wearable. Researchers at the Holst Center in the Netherlands presented the world’s first flexible, stretchable LED display which can be laminated onto textiles. The display is mounted on a polyimide substrate and encapsulated in rubber, meaning it is also washable. The technology uses production processes that are already established in manufacturing industry, so it can be quickly put into mass production. The second generation of the display presented in August 2015 has a resolution of 13 pixels per inch and an average brightness of more than 200 candelas per square metre.
Jeans for the next century
Clothing becomes really smart and user-friendly when electronics do not have to be built-in, but rather the fabric itself enables the functionality. Some time ago, a team headed by Huisheng Peng from Fudan University developed flexible, stretchable fibre-form supercapacitors for installation in e-textiles. And Google is currently working with jeans manufacturer Levi Strauss & Co. to develop a fabric which turns trousers into a touchpad. The technique involves weaving fine, conductive threads into the fabric. They allow tailored touch- and gesture-sensitive surfaces to be woven into any area of a garment. This means complete sensor networks can also be woven into trousers, creating large, interactive surfaces. They are connected to a main processor which processes all the data and relays them wirelessly to another wearable. So at the touch of a finger, the jeans can be used as an input device to a smartphone in the pocket, for example. Google demonstrated the project at its Google I/O developer show and has already shown that it is able to reproduce the standard functions of a touchpad such as cursor control and gesture input.
(Picture credits: A.Berns/Th. Scholl)