Fibre based electronic devices : Seminar topic

Weaving of electronics into any material

Scientists have always been known for doing impossible things and now a group of scientists from Massachusetts Institute of Technology (MIT) have done yet another thing by using two abundant raw materials to create fibre of pure crystalline silicon which could be used to add electronics, including microchips and solar cells, to almost any fabric.

The idea grew out of a long-term research effort to develop multifunctional fibres that incorporate different materials into a single long functional strand.

Until now, those long strands could only be created by arranging the materials in a large block or cylinder called a preform, which is then heated and stretched to create a thin fibre that is drastically smaller in diameter, but retains the same composition, but now for the first time, fibres created through this method can have a composition that's completely different from that of the starting materials.The new findings are described in paper in the journal 'Nature Communications' co-authored by Chong Hou, and six others at MIT and in Singapore.

The fibres are made from aluminium metal and silica, abundant low cost materials, which are commonly used to make window frames. The aluminium metal and silica glass react chemically as they are heated and drawn, producing a fibre with a core of pure, crystalline silicon-the raw material of computer chips and solar cells-and a coating of silica.

Hou tried a variety of metals, including silver, copper and aluminium-and in the latter case the result was not what they expected.When the scientists looked at the fibre, instead of a shiny metallic core, they observed a dark substance and they found that the core had silicon-in fact, very pure, crystalline silicon.It turned out that the chemical reaction in the fibre was well known one: At high temperatures used for drawing the fibre, about 2200 degree celsius, the pure aluminium core reacted with the silica, a form of silicon oxide.

This reaction left behind pure silicon, concentrated in the core of the fibre and aluminium oxide, which deposited a very thin layer of aluminium between the core and the silica cladding.

Now, Hou says,"We can use this to get electrical devices, like solar cells or transistors, or any silicon-based semiconductor devices, that could be built inside the fibre." Many teams, have tried to create such devices within fibres, he says, but so far all of the methods tried have required starting with expensive, high-purity silicon. A team is also working to produce specific structures, such as an electrical junction inside the material as it is drawn so that metals like gold or copper can be put in there to make a real electrical circuit.

Scientists also say that "This technology could open up new possibilities for electronics-including solar cells and microchips-to be incorporated into fibres and woven into clothing or accessories.    

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