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I'M A TRAVELING MAN

by Tom Cantrell

Start ı Key to the I-Way ı Itıs a Small World After All ı Sources and PDF

ITıS A SMALL WORLD AFTER ALL?

A trip to Sensors Expo is always fun because the show is in Anaheim, and the Disney influence lends a fantasyland feeling to the affair.

The latest developments on the sensor front are indeed fantastic, especially the excitement around micromachine technology and MEMS (micro electro-mechanical structures). They are tiny machines built in silicon, meaning they can be smart and connected. It also means that, like regular chips, theyıll cost less tomorrow.

Youıve probably heard the more tabloid-like predictions for micromachines, such as tiny robots that can go on a fantastic voyage through your body, roto-rootering the excess fries and pizza along the way.

People who are involved in the biz know that the micromachine concept isnıt a fantasy. In fact, micromachined devices (such as accelerometers and pressure sensors) already enjoy widespread commercial success.

But, thatıs just the start. Thereıs no shortage of interesting things to sense or folks who propose to sense them with some kind of micromachine. A micromachine sensor can mimic an earlier electro-mechanical version while taking advantage of the cost saving, size reduction, and the improved reliability and accuracy of silicon.

Consider the story at Hygrometrix Inc. As their name implies, theyıre in the business of making humidity sensors. For more than 30 years, Hygrometrix has offered what might best be described as an electro-organic humidity sensor comprised of strain gages connected to cellulose crystallite structures, which are harvested from the humidity sensitive seed-throwing mechanism of a geranium.

It sounds whimsical, but works well. Accuracy, linearity, and repeatability are all good, within a couple of percent or so, and the design tolerates environmental extremes. However, it is slow to respond (5 min. to react to a large step change) and expensive to produce.

Now, Hygrometrix has refreshed the design with MEMS technology. A polymer bonded to silicon reacts to water activity like the geranium, exerting force on a four-beam micromachined strain gage. The result is that the Hygrotron (see Photo 4) does everything the older flower power design did, only faster (5-s step change response) and at half the price!

Photo 4ıProve to yourself that it isnıt the heat, itıs the humidity with the micromachined Hygrotron from Hygrometrix.

Although the focus at the Sensors Expo is naturally biased toward sensing, MEMS technology can also be put to work. One of the first and perhaps best known example is the mirror arrays made by TI that are used in the latest high-end projection systems.

So besides sensing, expect to see plenty of MEMS actuator applications, such as the micromachined fluid valve from Lucas Novasensor (see Figure 3).

Figure 3ıLucas Novasensor shows off the micromachined fluid valve, which is basically a silicon squirt gun.

Computers are pretty good at seeing, feeling, and hearing, but smell is one human sense they havenıt acquired yet. Oops! I spoke too soon judging by the zNose from Electronic Sensor Technology.

I must confess, Iım not sure how the lashup of a six-port two-position sampling valve, a temperature programmed gas chromatography column, an integrated thermo-electric heating element, and a SAW (Surface Acoustic Wave) detector works. But, according to the company, itıs the only electronic nose to be validated by the EPA. Judging by the screen shot (see Photo 5), this vaporware is real!

Photo 5ıLess Filling? Tastes Great? Only the zNose knows.

I can only begin to contemplate the interesting applications posed by such technology. How about a home-brew halitosis detector, a body odor buster, or maybe even a dirty-diaper alarm? Donıt you just love this business?

Well, thatıs it for this report from the road. But donıt worry, the show season is just getting into full swing. It wonıt be long before Iım back pounding the floor, picking up press kits, praying I can find a cup of coffee, and loving every minute of it.

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