University of Alberta Edmonton, Canada 29 November 1996

Cantilever within a cantilever within a cantilever within a...

Team of University researchers invents switching/sensing device that may have commercial uses

By Michael Robb

It started out-like all good ideas-as a curiosity driven exploration. In the end, a team of University of Alberta Electrical engineering and mathematics students and professors and industrial partners has successfully designed a micro-machined cantilever device that could have a multitude of optical switching and sensing uses.

"This little device has generated a lot of interest," says team leader Sandy Robinson (Electrical Engineering). Adds co-researcher Walter Allegretto (Mathematical Sciences) it's a great example of what happens when the theoretical and the practical work comes together. "In this case, they're closely related."

The micro-machined device can be used as a deflectable mirror and a mass sensor. Really a nested array of cantilevers supporting a central flat leaf, the whole structure is made from two layers of conductor separated by a layer of insulation and supporting silicon dioxide. The nested cantilevers are nested within one another to increase its deflection capabilities.

The device is activated by current and magnetism. Other similar devices activated thermally typically have small deflections and slower response times, -10 milliseconds. The researchers point out that this device is fast, very fast, with a 25 microsecond response time-and that has obvious advantages in the microelectronics world where fast is good and faster is better.

"It can easily measure a change of mass of one nanogram, a thousandth of a millionth of a gram," explains Dr Robinson. And that may also end up being very useful for biomedical researchers, he points out, although that idea is really in its infancy. The growth of bacteria, for example, could be detected and measured; it would serve as a kind of mass biosensor, they speculate. Its ability to sense the presence of water and other fluids may also prove useful.

And like all good ideas in the microelectronics world, the drive is now on to miniaturize the whole system. Meanwhile, the device is receiving international recognition in trade journals.

Credit for the original idea goes to former Electrical Engineering graduate student Bing Shen, who is now working in industry. And the researchers have industrial partners. They have the assistance of the Canadian Microelectronics Corporation, Mitel and Nortel in the production of the device and assistance locally from the Alberta Microelectronic Centre and TRLabs. The Natural Sciences and Engineering Research Council is also funding some of the work. And several other professors, a visiting professor and graduate students are involved in the project.

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