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What appears to be an expensive studded dog collar is a new type of
flexible solar cell which its developers claim is cheaper and easier to
make than current photovoltaic cells which power devices ranging from satellites
to personal stereos. Photovoltaic cells convert sunlight directly into electric
current but are normally expensive because they are made from thin wafers
of very pure silicon. Texas Instruments and Southern California Edison have
developed a process for turning cheap low-grade silicon into tiny spheres
of pure silicon which they then fix onto a thin aluminium foil, 17 000 spheres
to each 10-centimetre square. The spheres are tougher than wafers and as
each sphere is an independent working cell, if it breaks down it will not
affect the rest of the array.