Chemical engineers at the University of Wisconsin-Madison have developed a new way to create inexpensive chemical sensors for detecting explosives, industrial pollutants, or even the chemical markers of disease in a patient’s breath.
The idea came from two chemical and biological engineering professors, Manos Mavrikakis and Nicholas L. Abbott. By combining their expertise in computational chemistry and liquid crystals, the duo turned a sensor Abbott built to detect a molecular mimic of deadly sarin gas into a roadmap for tuning similar sensors to flag other dangerous or important chemicals.
The team's framework is a new approach for optimizing the components — similar to those found in flat-panel TVs — of a liquid-crystal-based sensor: metal cations (which are positively charged ions), salt anions, solvents, and molecules that form liquid crystals.
The research leveraged Mavrikakis' computational chemistry expertise and Abbott's experimental expertise, cycling between quantum chemical modeling and the laboratory experiments to optimize the sensor components for a targeted substance. By tweaking the individual components in turn, they identified a configuration that specifically responded to the molecule they wanted to sense, called the analyte. This same approach could also yield new sensors for a host of different analytes.
Looking to the future, such materials could be used to indicate the freshness of fish or meat based on the presence of the molecule cadaverine. Another variation could be used to detect respiratory diseases based on analysis of small molecules, such as nitric oxide in breath.
Consisting of a thin film of metal salt, the sensor material's liquid crystals are anchored to the surface, all pointing in the same direction. The researchers designed specific liquid crystal molecules and metal cations so that small amounts of analyte would disrupt the interactions of the liquid crystals with the surface, and throw the ordered arrangement into disarray. This is because the change in the liquid crystal would be a visible indicator of the analyte's presence.
Unlike expensive explosive-detecting puffer machines in airports that rely on complicated mass spectrometry or high-performance liquid chromatography equipment, the liquid crystal sensors could be portable, wearable and inexpensive.
The researchers plan to explore new combinations for additional analytes and develop new liquid crystalline molecules, in combination with other metal salts and solvents, to make more sensitive and selective sensors.
Source: Eureka Alert!
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