Researchers have found the secret to improving a robot's sense of smell: Shove frog eggs up its nose. A team at the University of Tokyo has developed a sensor made from a genetically modified frog egg that can help a robot pick out insect smells and pheromones. As useful as a moth-smelling robot may seem, researchers believe the study published yesterday in Proceedings of the National Academy of Sciences is just one step towards an inexpensive but sensitive chemical detector. Study coauthor Shoji Takeuchi explains that such a device could pick out gases like carbon dioxide:

"When you think about the mosquito, it is able to find people because of carbon dioxide from the human. So the mosquito has CO2 receptors. When we can (extract) DNA (from the mosquito) we can put this DNA into the frog eggs to detect CO2." [Reuters]

Here's how they did it. Step 1 -- Get Some Frog EggsThough this is the first time they've appeared in a robot, the team says, genetically modified African clawed frog (Xenopus laevis) eggs have helped others labs to make detectors.

“People for many years, my lab especially, have been involved in work using Xenopus oocytes to express olfactory receptors,” said Laurence Zwiebel, professor at Vanderbilt University who was not involved in the study. “It’s a very convenient system; it’s essentially a little factory cell that you can harvest very easily and make it work for you.” [LiveScience]

Step 2 -- Add Some Bug DNA By injecting the immature egg cells with silkmoth, diamondback moth, and fruit fly DNA, Takeuchi and his colleagues spurred the frog eggs to produce those insects' olfactory receptors.

He likened the eggs to "platforms" and said studies in the past found that certain segments of DNA from the three insects were responsible for detecting odors and gases."We inject DNA into the frog eggs and then we can make some very useful and inexpensive sensors," said Takeuchi. [Reuters]

Step 3 -- Shake Vigorously The detectors--about the size of a matchbook--measure currents created when the eggs' smell receptors bind with odor molecules. This makes a much more sensitive biological smelling system than current sniffers which use physical vibrations.

Although e-noses have been around for a while--and are used to sniff out rotten food in production lines--they lack accuracy. That's because e-noses use quartz rods designed to vibrate at a different frequency when they bind to a target substance. But this is not a foolproof system, as subtly different substances with similar molecular weights may bind to the rod, producing a false positive. [New Scientist]

Finally researchers added the egg detectors to a robotic mannequin torso and head. When sprayed with moth pheromones, the robot gave a disagreeing head shake (see video). Hopefully it can one day do the same when it inhales a face full of CO2.

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Images: Nobuo Misawa, Hidefumi Mitsuno, Ryohei Kanzaki, and Shoji Takeuchi