Electronic "Tongue" For Environmental Monitoring

The researchers, based at Cardiff University’s School of Engineering, have demonstrated that the ‘tasting’ part of the system can be fabricated from very small components, making it potentially easy and inexpensive to mass-produce. The next step would be to link the tongue to a computerised ‘brain’ to analyse the signals it generates.

The work is being carried out by Professor David Barrow’s team, with funding from the Swindon based Engineering and Physical Sciences Research Council (EPSRC).

The system is based on an analytical technique called chromatography (a technique for separating mixtures). Here, the chemical sample, contained in a liquid or a gas, is passed through or over a solid ‘matrix’ which has a high surface area – for example a glass cylinder packed with silica beads. It is possible to attach a variety of chemical ‘hooks’ on to the beads, so that as the sample passes down the column of beads different components will be ‘grabbed’ by the hooks to differing extents. In this way the various components can be separated from the mixture and analysed.

The Cardiff researchers’ system works on broadly similar principles, but on a much smaller scale. If a silicon chip is treated with hydrofluoric acid in a controlled way, it becomes etched with millions of tiny pores and channels, of dimensions of nanometres. “So if you etch a spot a millimetre square, you actually have several square metres of internal surface area,” says Professor Barrow. “It is in effect a tiny chromatographic ‘extraction cartridge’.”

“You could put the system in a river or factory process stream to monitor the mixtures flowing through it,” says Professor Barrow.