Liquid crystals, the visual element in products like digital watches and computer monitors may help in the quest for early detection of pathogens.
Developed by Professor Nicholas Abbott and doctoral student Justin Skaife, chemical engineers at UW-Madison, the advance could be especially useful for detecting serious pathogens like foot and mouth disease, West Nile virus, cryptosporidum or E. coli.
By using liquid crystals in combination with nanostructured surfaces, Abbott said his credit-card sized plastic chips could offer rapid detection of bacteria or a virus.
Liquid crystals are said to make effective optical amplifiers because their molecules tend to line up with each other over long distances, forming long strands of up to a million molecules.
When exposed to a specific pathogen, this tendency to organise will make the presence of microscopic bugs visible to the naked eye.
Abbott first noticed this phenomenon in 1998, when he published an article in the journal Science showing how liquid crystals can amplify the binding of proteins on surfaces.
That advance could be useful, for example, in detecting antibodies and other proteins in blood samples without the need for labels. But this patent, filed a year later showed that liquid crystals can also be used to detect entire organisms.
The researchers first used techniques of nanofabrication to alter the surface of their device with ridges and bumps that match the size of contours of a species of virus or bacteria.
Their next step involved exposing the surface to a water or soil sample from the field. Then the liquid crystal surface was laid over the surface.
If the sample contained a pathogen then liquid crystals respond by changing their colour or brightness, in the same way a computer monitor reacts to electrical fields.
‘We’re seeing an increasing focus on food pathogens and emerging diseases, especially with the greater movement of people and products around the world,’ Abbott said. ‘We really don’t have methods of detection in use now that are rapid, robust and inexpensive,’ he concluded.