Affordable chemical sensor designed with liquid crystal

A new method in developing chemical sensors for flagging dangerous or important chemicals has been discovered by a team of chemical engineers at Madison. The method can be used to detect pollutants, explosives as well as chemical markers of disease from a person’s breath.

Madison professors Manos Mavrikakis and Nicholas Abbott are the men behind the discovery. Abbott, an expert in liquid crystals, previously built a chemical sensor and

Mavrikakis used his expertise in computational chemistry to improve on it so that the sensor may now detect a molecular mimic of dangerous sarin gas.

The framework that Mavrikakis and Abbott created aims to optimize metal cations, salt anions, solvents and molecules which built up liquid crystals. Note that the same liquid crystals are used on TV and computer displays.

With this research, the computational chemistry prowess of Mavrikakis and the experimental wizardry of Abbott were challenged to create a method to optimize the sensor components for a specific chemical substance. The optimization lead to a sensor that responds to a target molecule which is called the analyte.

New sensors for a lot more analytes could be created using the same method in the future. Besides dangerous chemicals, the materials that the team created could be used to detect if a fish is fresh or not based on the trace amount of foul-smelling molecule cadaverine. Another application is the detection of nitric oxide in breath for diagnosis of a respiratory disease.

It’s a challenge for Abbott and his team to create such specific and sensitive materials in the laboratory. And It is laborious to mix chemicals to obtain perfectly matched multiple components. It would take years if the team carried out trial and error experiments, and this is why they prefer computer simulations before trying them out experimentally.

“This is indeed the first time that computational chemistry with quantum mechanics has been used to put together a coherent way of thinking for narrowing down possible solutions for an explosively complicated problem,” says Mavrikakis.

The sensor is made out of a thin film of metal salt. On this material are liquid crystals attached to the surface all pointing at a specific orientation. The special liquid crystal molecules designed by the researchers are developed along with metal cations so that only minute amounts of analyte are needed to rattle the otherwise ordered interface between the liquid crystal and the surface. This disarray is an indicator that the analyte is present.

Airports use mass spectometry or high-performance liquid chromatography to detect explosive materials in their vicinity. However, this technology is not only expensive but also complicated. The liquid crystal sensors that Mavrikakis and Abbott developed are wearable and relatively cheap.

In the future, the researchers would like to try on new combinations of liquid crystalline molecules, metal salts and solvents in hopes of creating more sensitive and selective sensors.


More information can be found at: University of Wisconsin.

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