Electronics, All Dressed UpNovember 13, 2015 By: Jeroen van den Brand PhD, Holst Centre
These days we all carry electronics around with us. Sometimes even a bit too much. So imagine if you could integrate some of these functions into the clothes you wear. This article shows how to produce flexible and stretchable clothing fabric that incorporates electronics. And who knows, maybe in a few years these textiles will be starring on the catwalk in sports, health, and safety clothing.
Why should we integrate electronics into clothing?
Ask an expert in wearable electronics about the future and he'll start dreaming about sensor bracelets, smart glasses, heart-monitoring patches and so. These dreams almost make our so-essential smartphone pale into insignificance. Because clothing and textiles are certainly not to be overlooked. In fact, they make the ideal platform for wearable electronics.
That's because clothing has many advantages over the examples mentioned above. First of all, clothes are something you have to wear anyway. You can forget your smartphone or sensor bracelet, but you won't forget to pull on a T-shirt or other garment. A second advantage is that clothing covers your whole body. This is important if you want to wear sensors that monitor your health or display lights that make you visible when you're riding your bike in the dark. And, finally, clothes help to make technology become invisible. For example, you can't see that you're wearing a heart monitor if it's integrated invisibly into your T-shirt.
Easier said than done
While you can already find examples of smart clothing on the market, it's still only a tiny taste of what is going to come. The smart clothing you find today still uses standard electronics in rigid form. Also, it includes tight-fitting clothing when sensors are involved. But if you're a heart patient, you probably don't want to wear a tight sensor T-shirt every day. Plus, at the moment, the functionality of smart clothing is still very basic. It can only get better.
Holst Centre kicked off the 'Smart Garment' program in 2014 because the researchers there believe that they have the technology needed to take smart clothing to a higher level. However, it promises to be anything but a straightforward exercise.
If you are going to incorporate electronics into fabrics, the material itself must not lose its intrinsic properties. If your T-shirt doesn't feel soft and the fabric can't breathe, or if it doesn't fall nicely round your body and you can't wash it, then you won't wear it for very long. And if it's expensive as well, you won't buy it in the first place. So we have to develop a technology that enables us to make inexpensive, thin, flexible and stretchable electronics that can easily be integrated at various locations on the garment. And not just one type of electronics, but various functionalities: visual displays, LEDs, sensors and actuators, antennas and radios for wireless connection, switches and so on.
Foil with printed electronics
Holst Centre is developing system-in-foil (SiF) technology, which enables electronics to be printed on large sheets. This is of interest for solar cells and for RFID tags that have to be integrated into packaging, as well as for smart clothing. Jeroen:
Using SiF technology you can produce thin, flexible and inexpensive electronic foil sheets. You start with a polyester sheet just 25 to 50 micrometers thick. You then 'print' your electronics on it. This is the ideal technique if price is important and you want to work with large surface areas. The polymers applied through the printing process are also flexible, which means that the foil retains its intrinsic properties. Working like this, we have been successful in producing circuits with multiple layers (four, to be precise), as well as passive components, sensors, OLEDs, and solar cells. Of course, it's not possible to print everything, which is why it is also important to develop a good integration technology enabling you to work standard components such as LEDs and microcontrollers nicely into the foil. This is something else we have demonstrated successfully.
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