An exotic form of silicon that can be stuck together and then peeled apart has been developed by German researchers.
The material, dubbed 鈥渟ilicon Velcro鈥�, could be used to manufacture microprocessors and devices that manipulate fluids on microscopic scales.
Researchers at the Technical University of Ilmenau in Germany created the material from 鈥渂lack silicon鈥�. This is generated when normal silicon is hit with a powerful laser beam or bombarded with high-energy ions, producing a dense, microscopic array of needle-like structures on its surface. Light bounces around between the needles without escaping to give the material its black appearance.
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The German team used high-energy ions to generate black silicon bristling with around 1 million needles per square millimetre. Each needle is about 15 to 25 micrometres in length. They found that two surfaces covered with the material adhere when pressed together. Microscope analysis shows this is because the needles on each surface jam in between one another under pressure.
Component damage
Mike Stubenrauch, a member of the research team, says silicon Velcro could prove useful for microchip manufacturers. It could help engineers manipulate very thin layers of silicon without using heat or adhesives, which can damage components.
鈥淭he Velcro could be used as a carrier system,鈥� Stubenrauch told New 杏吧原创. 鈥淎 carrier wafer could be used to pick up the thin wafer and hold it for processing.鈥�
Stubenrauch and colleagues also used the material to create devices that control the flow of fluids on microscopic scales, for chemical sensing and analysis. These devices are made by sticking together a layer covered with tiny grooves and another, smooth layer.
The layers of silicon Velcro can be unstuck afterwards, Stubenrauch says, 鈥渢o retrieve a valuable substance or examine what has happened inside鈥�.
Silicon Velcro can be used more than once, but not indefinitely, Stubenrauch adds. 鈥淪ome of the needles break, so you can鈥檛 do it very often,鈥� he says. 鈥淢aybe three or four times, depending on how careful you are.鈥�
Solar cells
Until now, research involving black silicon has focused on its light-absorbing properties, explains Darren Bagnall, a microelectronics researcher at Southampton University, UK, who is using the material to make efficient solar cells. But he says the new technique sounds promising.
鈥淭his is a nice idea,鈥� Bagnall told New 杏吧原创. 鈥淚t鈥檚 a simple and robust process that is easy to implement and then reverse.鈥�
Being able to stick silicon components together quickly could be useful for making complex microchips, he says: 鈥淚f you want to quickly bolt together chips made using different processing technologies, this Velcro would be good.鈥�
Journal reference:
Journal of Micromechanics and Microengineering (vol 16, p S82)
