Sensors Mag

May R&D Round Up

May 4, 2012 By: Melanie Martella, Sensors

E-mail Melanie Martella

This month we have a mini sensor that measures the magnetic activity that happens inside your head and a sensor to measure just how ripe (or unripe) that apple is.

Measuring Magnetic Brain Activity
So, you first met this particular sensor back in 2010, when it had been used to measure the magnetic signature of a beating human heart. Not content with its ability to measure said magnetic signature down to 1 picotesla, the NIST and German researchers have improved the device's signal clarity and have now proved that it can be used to measure alpha waves, generated in the patient's brain when the patient moved their hand and shut and opened their eyes. As described in the article "NIST Mini-sensor Measures Magnetic Activity in Human Brain", the sensor is still built around a container in which sit some 100 billion rubidium atoms in a gas, coupled with a low-power IR laser (because, it turns out, rubidium atoms absorb more light the stronger the magnetic field), and fiber-optics to detect the light. While the new sensor isn't as sensitive as a SQUID, which is the gold-standard for making very tiny magnetic field measurements, it is much smaller, operates at room temperature, and (ideally) it'll end up being much cheaper to manufacture than current atomic magnetometers. Small sensors are easier to use on patients; the researchers hope that they could be used in magnetoencephalography (MEG) to make the process of taking the needed measurements less unwieldy and more useful.

Spotting Ripe Fruit
The adage "one bad apple will spoil the whole barrel" is really a tale of ethylene and its crazy fruit-ripening powers. Ethylene can be used to ripen unripened fruit or, if you happen to have a warehouse full of fruit that you want to keep in tip-top condition, you can strive to keep the ethylene concentration low (and by low, the typical concentration required to ripen fruit is between 0.1 and 1 ppm). The problem with existing systems that monitor ethylene concentration is that they're expensive. But what if you could put an inexpensive ethylene sensor onto every box of fruit? Wouldn't that allow retailers to manage food spoilage better? Well, that's the general idea behind MIT chemistry professor Timothy Swager and his students and the novel sensor they've developed The sensor uses carbon nanotubes doped with copper. When ethylene bonds with the copper atoms, the resistance of the carbon nanotubes increases. By adding tiny polystyrene beads (which absorb the ethylene and thus concentrate it), that resistance change is increased and the sensor's sensitivity is boosted. The article, "Comparing apples and oranges", describes the motivation and results of the project; the researchers have managed to detect ethylene concentrations as low as 0.5 ppm!

About the Author: Melanie Martella

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