Transistors made from cotton yarn, t-shirt computers incoming
By Sebastian Anthony
 
Altering the very fabric of technophilic  society, a multinational team of material scientists have created  electric circuits and transistors out of cotton fibers. Two kinds of  transistor were created: a field-effect transistor (FET), much like the transistors found in your computer&rsquo;s CPU; and an  electrochemical transistor, which is similar but capable of switching at  lower voltages, and thus better suited for wearable computers.
If  you&rsquo;re like me, you&rsquo;re probably thinking that cotton is a very strong  insulator and not at all conducive to conductiveness &mdash; but before you  accuse this team from Italy, France, and the United States of witchcraft  and wizardry, bear in mind that they kind of cheated. Cotton is just the substrate: To make it conductive, the researchers coated cotton threads in a variety of other materials. To make conductive  &ldquo;wires,&rdquo; the team coated the threads with gold nanoparticles, and then a  conductive polymer. To turn a cotton wire into a semiconductor, it was  dipped in another polymer, and then a further glycol coating to make it  waterproof.
The end result, according to the research paper,  is cotton yarns that can be used to fashion the basic building blocks  of a computer circuit, but still retain their flexibility. Because of  the coatings the threads are slightly stiffer, but on the flip side they  are more elastic, too. It is not a time-consuming process to create  these conductive cotton threads, either: It&rsquo;s comparable to dyeing.
These  tailor-made cotton circuits will weave the way to, quite literally,  wearable computers. For the first time, instead of incorporating small  chips or flexible printed circuits,  you will be able to build a t-shirt that is also a computer. Just think  how many interconnections there are in a standard cotton shirt &mdash; it&rsquo;s  on the scale of hundreds of thousands or millions &mdash; and each one could  become a transistor. We&rsquo;re obviously a little way away from that  reality, but the idea of incorporating sensors &mdash; radiation detectors,  toxic substance detectors, heart beat monitors &mdash; is just around the  corner.
Imagine the high-tech grandmother of tomorrow, too:  Instead of knitting you a crappy Christmas sweater, she could knit a  sweater with a built-in GPS unit, and love-handle sensors that alert her  when your body-mass index reaches dangerously low levels.
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