Sensors Mag

May R&D Round Up

May 7, 2010 By: Melanie Martella, Sensors

E-mail Melanie Martella

This month we've got a sensor that can detect microfissures in large, architectural glass panels, providing early warning of potential breakages; a wireless, passive fluid measurement sensor; and a tattoo-like experimental blood glucose sensor.

Sensing Damage to Glass Panels
Considering the prevalence of huge glass windows in modern buildings, and how very, very bad it is when those windows break or fall, some way to check the health of the glass panels seems like a very good idea. On the one hand, glass break sensors exist but only notify when the glass actually breaks. Which, if you're a pedestrian down below who's just had to dodge a falling window, is a bit late. A team of researchers from Fraunhofer Institute for Silicate Research (ISC), working with industrial partners, have developed a sensor that can detect tiny cracks—microfissures—in glass panels before they're visible to the naked eye, thus giving an early warning of damage. The researchers placed four 15 by 15 by 0.5 mm piezoelectric sensor actuator modules on the edge of a pane of glass, placed 1 m away from each other. One module emits an ultrasonic tone which is detected by the other three modules. If the tone doesn't change, then the glass is sound and no problems are present. But if the tone changes, that signals a problem and the pane can be replaced or repaired long before it is in danger of breaking. The sensors can also be used to detect damage incurred during transport and the researchers have even managed to insert them between sheets of laminated glass. For more on this story, read the article "Sensor predicts glass breakage" from

A Novel Fluid Sensor
Here's a handy development from the clever people at NASA Langley, a wireless thin-film sensor that can be used to measure fluids from inside or outside a closed container. The thin-film sensor is a spiral electrical trace on a flexible substrate. When the companion magnetic-field DA system is set to transmit, the sensor receives the signal and, in response, produces its own harmonic magnetic field. When the DA system is set to receive, it acquires the magnetic-field response of the sensor, which is affected by the fluid it's measuring. If it's immersed, the depth of the immersion will affect the sensor's frequency response. By placing three or more sensors within the container, you can acquire volume measurements as well as measure pitch and roll, since each sensor will provide a different level measurement. While this is of greatest benefit to those trying to measure fuels without having to open the tanks, the technology can be applied to all kinds of nongaseous materials. (Be sure to follow the link to see a video of the system in action.)

Sensor Tattoos for Diabetics?
While modern glucose monitoring systems require far small volumes of blood than earlier versions, they still involve the patient having to prick their fingers on frequent basis. But, if Dr. Heather Clark and her fellow researchers at Draper Laboratory have their way, those patients could end up throwing out their lancets for good. The researchers have developed a glucose-sensitive nanosensor that responds to changing glucose concentrations with changes in fluorescence. By embedding the sensors into skin, patients could monitor their blood glucose levels by monitoring the fluorescence changes. To learn more, read "The Glucose-Monitoring Tattoo" from MIT Technology Review.

About the Author: Melanie Martella

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