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Selective sensing of harmful molecules with light: surface plasmon resonance (SPR) devices are the benchmark in optical sensing. They are used for detecting biomarkers of diseases, discovering drugs, analysing chemicals, ensuring food quality and safety, and detecting pollutants in the environment. Now, scientists are developing more highly sensitive devices for the detection of biological and chemical compounds.

few hundred nanometres of their metal surfaces. When a target molecule binds to sensing molecules placed on the device's surface, this alters the path of light travelling through the medium, changing its refractive index. This change is used to indicate the presence of the molecule.

Now, scientists Brian Corbett and Muhammad Khan of University College Cork in Ireland are working on improving the sensitivity, compactness and cost of SPR devices by changing the materials used to make them.

Bloch Surface Waves (BSW) are light waves that travel on the surface of insulating--or dielectric--materials, such as glass. Researchers are testing the use of dielectric materials, instead of the metals typically used for the surfaces of SPR devices, to develop BSW devices. By doing so, they are detecting even smaller changes in the material's refractive index.

"Bloch surface waves can be used for a variety of sensing applications," says Corbett. "This research has taken place mainly in the last 10 years, with demonstrations in sensing vapours, various biomarkers, and protein aggregation, for example. They can also be potentially used as a platform for compact integrated optical circuits." Corbett expects BSW devices to become commercially available in the coming few years.




Corbett and Khan have designed a simple BSW sensor, employing silicon as its surface material, which they believe has practical advantages due to the ease with which it delivers and detects light waves.

"The research shows that surface waves can be easily generated and they provide a sensitive measure to detect the binding of a material at a surface," says Corbett. "The sensor surface is simple and easy to fabricate with sensitivities comparable to and better than SPR sensors. These sensors can provide real-time sensing and may be a way to screen at the doctor's surgery for the presence of biomarkers for different diseases, such as cancer and Alzheimer's."

According to Corbett, the sensors still need to be tested for their durability in real environments. The team's aim is to develop an on-chip sensing platform with high sensitivity that can ultimately be used in benchtop or even smartphone-based devices, with potential applications in water guality monitoring.

>> Reference: Brian Corbett and Muhammad Khan: "Bloch surface wave structures for high sensitivity detection and compact wavequiding," Science and Technology of Advanced Materials Vol. 17 (2016) p. 1202082.

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Title Annotation:DESIGN IDEAS
Publication:Environmental Engineering
Date:Aug 1, 2016
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