Since this new sensor allows water and air samples to be analyzed in the field, it is an improvement over classical techniques that require samples be carried back to the laboratory for analysis. This research, funded by the National Science Foundation, was presented on August 20 at the American Chemical Society’s 234th National Meeting.
The heart of the disk-shaped sensor is a microbalance that measures the mass of pollutant molecules.
“When pollutant chemicals get adsorbed to the surface of the sensor, a frequency change of the vibrating microbalance provides a measure of the associated mass change,” said Oliver Brand, associate professor in Georgia Tech’s School of Electrical and Computer Engineering.
Since each sensor has a diameter of approximately 200-300 microns, or the average diameter of a human hair, an array of a dozen sensors is only a few millimeters in size.
To determine how to selectively detect multiple pollutants in the same sample, Brand began collaborating with Boris Mizaikoff, an associate professor in Georgia Tech’s School of Chemistry and Biochemistry and director of its Applied Sensors Laboratory.
Mizaikoff and graduate students Gary Dobbs and Yuliya Luzinova selected commercially available hydrophobic polymers and deposited them as thin film membranes on the sensor surface. They continue to investigate innovative ways to consistently deposit the polymers at the disk surface, while ensuring sufficient adhesion for long-term field applications.
“By modifying the silicon transducer surface with different polymer membranes, each sensor becomes selective for groups of chemicals,” explained Mizaikoff.An array of these sensors, each sensor with a different chemically modified transducer surface, can sense different pollutants in a variety of environments ranging from industrial to environmental and biomedical monitoring applications.
A common VOC is benzene, with a maximum contaminant level set by the Environmental Protection Agency (EPA) at five micrograms per liter in drinking water. Many VOCs are present at similar very low concentrations, so effective sensors must accurately measure and discriminate very small mass changes.
“We’ve been able to measure concentrations among the lowest levels that have been achieved using this type of resonant microsensor,” noted Brand. “While we have not achieved the required sensitivity yet, we are constantly making improvements.”
Brand and Mizaikoff have tested their sensor device in the laboratory by pumping water with specific pollutant concentrations through a simple flow cell device attached to the sensor.
A typical test begins by flowing a water sample containing a known amount of pollutant over a sensor coated with a polymer membrane. When the sample flows through the cell, the mass of the microstructure increases, causing its characteristic vibration frequency, or resonance frequency, to decrease. By monitoring this resonance frequency over time, Brand and Mizaikoff can detect the amount of aromatic hydrocarbons such as benzene present in water.
The researchers plan to run field trials to investigate the use of this new microsensor in aqueous and gaseous environments for rapid on-site screening of multiple pollutants.
“With benzene and other VOCs high on the EPA priority pollutant list, it would be a major advantage to get a rapid reading of VOC concentrations directly in the field,” said Mizaikoff.
John Toon | EurekAlert!
A Map of the Cell’s Power Station
18.08.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau
On the way to developing a new active ingredient against chronic infections
18.08.2017 | Deutsches Zentrum für Infektionsforschung
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
18.08.2017 | Life Sciences
18.08.2017 | Physics and Astronomy
18.08.2017 | Materials Sciences