1 April 2002
Big plans for mini electronic nose
Warwick, England—Where can you find the world’s smallest nose? Sniff out the answer across the pond in the U.K., where engineers and scientists from the universities of Warwick, Leicester, and Edinburgh are working on building the world’s smallest electronic nose.
The goal is to combine odor sensors with signal processing components on a single silicon chip about a square centimeter. The instrument would require little power and could fit in your palm.
Electronic noses have been around for years. They sniff out problems in the food, beverage, and perfumery industries. But they are large, have limited sensitivity, and frequently need recalibration.
"We are taking recent developments in the fields of nanotechnology and polymer physics to design novel microsystems that are able to mimic our nasal passages and olfactory sensors," said University of Warwick engineering professor Julian Gardner. "Combining such technologies with biologically inspired signal processing methods developed at Leicester and Edinburgh should lead to a new generation of so-called micronoses, or a nose on a chip."
"We are hoping we can improve on existing systems by following biology much more closely," said Dr. Tim Pearce of Leicester University. "The information processing of our system is very much inspired by how the olfactory system works in nature."
The sensing part of the device will consist of arrays of electrically conductive polymers.
However, the new system will process and interpret signals in a way much more akin to biology.
"When sufficient numbers of odor molecules interact with an olfactory receptor neuron in the real nose, an action potential is induced—a spike of voltage that is sent down a nerve fiber to be processed by the olfactory pathway of the brain," Dr. Pearce said. "We will design our system to do a similar thing. If there is a high concentration of odor molecules, trains of spikes will be generated, and their frequency will be proportional to the concentration of the molecule."
This "neuromorphic" approach introduces a time factor into the system—the number of spikes per second—unlike the signals in conventional electronic noses. This gives the signal processor another layer of information that could be useful, for example, when trying to distinguish among complex mixtures of odor molecules.
At Edinburgh, Dr. Alister Hamilton’s team is devising ways to integrate the whole system on to a single silicon chip. "We are designing analog circuits that interface to the sensor array developed at Warwick and sending the signals into some analog circuits that mimic the mammalian olfactory system," he said. "We’re using parallel analog computation strategies that are derived from biology rather than implementing a conventional digital processor. By concentrating on very low power consumption analog circuits, we hope to produce a system with long battery life."