MEMORY CUBE BREAKS RECORD
The promise of pocket-sized storage devices that can hold not only your music collection but your entire DVD library too has been around for over a decade, thanks to a device called an optical cube that can cram in 1000 gigabytes (New 杏吧原创, 13 August 1994, p 22). The problem is that no one has yet managed to read or write the data fast enough to make them viable as a commercial device.
Now a team lead by Masaharu Nakano at Shizuoka University, Japan, has created a nanoscale structure that can store 2000 gigabytes of data in a 1-cubic-centimetre cube. The cube comprises eight layers of photosensitive urethane-urea copolymer, separated by layers of transparent polyvinyl alcohol.
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Data is recorded using a red laser with a wavelength of 790 nanometres in a way that controls the shape and spacing of individual bits, providing clear spacing between them. It is then read using UV light from a helium-neon laser with a wavelength of 0.6 nanometres.
The device breaks the current storage record for an optical cube. Sadly, reading and writing data still takes too long for it to be of any practical use.
SOLAR CELLS CASH IN ON UV LIGHT
A film of silicon nanoparticles might boost the efficiency of existing photovoltaic cells by capturing previously wasted ultraviolet photons.
While silicon in today鈥檚 solar panels can convert visible light into electrical energy, all that is produced from any UV absorbed is heat. Now a group of physicists from the University of Illinois at Urbana-Champaign have found that chopping up silicon into particles just 1 nanometre across allows the solar panels to make electricity from UV radiation too.
The team deposited a thin film of nanoparticles, made by electrochemical etching, onto a silicon base and blasted it with UV. The resulting film performed about 8 times as well as standard UV sensitive materials, producing around 750 milliamps per watt of UV light.
The film can be combined with existing solar cells to boost their output by as much as 10 per cent, the researchers say. It could also prevent solar cells overheating, especially in space, where UV levels are much higher.
Economics will determine the use of the new film, according to Eric Mazur, a physicist at Harvard University. 鈥淚f it costs twice as much to make a 10 per cent improvement, it won鈥檛 sell.鈥�
