Nickel’s high-tech potential

In a technological age that promises to miniaturize everything from motors to computer chips, nickel is expected to play an increasingly important role. The emerging field of micro-electro-mechanical systems (MEMS) is a case in point.

MEMS are tiny mechanical components — some no larger than a grain of sand — that usually contain integrated electronics. A handful have already found commercial applications, from silicon-based pressure transducers that provide precise measurements for medical monitoring to sensors designed to activate airbags in cars.

Industry observers predict that MEMS will do for mechanical components what microchips did for electronics. Indeed, the MEMS market is expected to grow to more than US$5 billion by 2002, according to Cronos Integrated Microsystems, the first commercial enterprise to focus exclusively on MEMS products.

Some MEMS, including those applicable to biomedicine (such as protheses), defense systems (such as sensors for detecting biological and chemical weapons) and portable consumer products, require three-dimensional metallic components. This is where nickel comes in.

Electro-deposited nickel gives structural integrity to 3-D components. In fact, micro-electrodeposition can be thought of as the small-scale equivalent of casting and welding used to manufacture structures at the macro level, says George Whitesides, professor of chemistry at Harvard University.

“The actual amount of nickel is minuscule, but the value that nickel provides is very high,” he says.

Whitesides is testing nickel for use in 3-D metallic structures, ranging from heat exchangers to components of small aircraft. His team combines electrodeposition with lithography, a set of techniques for pattern transfer, to build micro-trusses.

“The reason for working with nickel is that it responds to electro-chemistry, has good mechanical and corrosion properties, and is inexpensive,” says Whitesides.

For example, one technique routinely produces metal features at the 1-to-100-micrometre scale. Electrodeposition then transforms the planar metallic structure into miniature 3-D devices by joining together the separate 2-D components.

Nickel could even be used in biomedical applications, such as implants that dispense drugs, in which case the metal would likely be coated to prevent possible allergic reactions. The metal’s magnetic properties make it a natural choice for magnetic applications.

Alternative metals for 3-D applications include welded copper, material that has been machined out of silicon and, for biomedical purposes, stainless steel, titanium and gold.

By testing several different materials, the Harvard team hopes to develop micro-structures that cannot be produced economically by conventional means.

“We reached the point where we can demonstrate clearly that one can make interesting structures,” says Whitesides. “Now the question is, Are those structures sufficiently interesting that they will be worth someone’s effort to commercialize?”

Once the components pass applications testing, commercialization should be relatively problem-free, given that the devices are uncomplicated and inexpensive to produce.

— The preceeding is an excerpt from Nickel, a publication of the Nickel Devlopment Institute, based in Toronto.