Silicon chips posses multi-faceted properties

Chemists at the University of California, San Diego have discovered that silicon wafers can be easily made into tiny explosives that could be used to chemically analyse samples in the field or serve as power sources for tiny electronic sensors the size of a speck of dust.

"Most people are familiar with silicon as the material that is used in computer chips for circuits," says Michael Sailor, a professor of chemistry and biochemistry who headed the research project. "This is the same material, but we are making it into a very finely divided form of silicon, a nanocrystal, that has such a high surface area that it burns very quickly. The faster the burn, the bigger the bang."

Like gunpowder (a mixture of carbon, potassium nitrate and sulphur) the UCSD scientists knew previously that a silicon-based explosive would explode when mixed with potassium nitrate. However, Frederic Mikulec, a postdoctoral researcher in Sailor's laboratory, discovered by accident while working with a porous wafer of silicon that substituting potassium nitrate with gadolinium nitrate had the same effect.

"When he tried to cleave the wafer with a diamond scribe, it blew up in his face," recalls Sailor. "It was just a small explosion, like a cap going off in a cap gun. But it really surprised us, so we started looking more closely at it, because the gadolinium produced a very clean burning flame."

The absence of chemical impurities makes the gadolinium and silicon-based explosive ideal for use in a device that could perform rapid chemical analysis of toxic metals and other elements in the field.

Moreover, current manufacturing processes for computers could be easily adapted to produce such smart explosive or propulsion systems. "One of the things we have shown is that the construction of this explosive is compatible with conventional silicon fabrication techniques," adds Sailor. "In other words, the same tools that right now can put transistors on a chip could be used to build a rocket motor using the same material, silicon, that forms the chip as the power source."