Response to colour is said to be a subjective matter, but a jeweller grading a diamond cannot allow philosophical issues to cloud his judgement. Now, a tiny spectrometer from the German company MicroParts could help him to analyse stones with scientific certainty.

Claimed to be the world’s smallest spectrometer – it easily fits into a matchbox – the spectrometer is particularly suitable for designing portable and hand-held instruments. Dentists already use the spectrometer to obtain an exact match between their patients’ teeth and dentures. One of MicroParts’ customers has even developed an instrument to check the skin colour of newborn babies for the diagnosis of hepatitis. Another potential use is in auto spray shops, where the colour of the paint must be adjusted to match the fading of the car’s colour over a period of several years.

Miniature laboratories are another exciting field, where the tiny spectrometers can be integrated with capillary based fluid sampling system. These hand-held instruments can, for example, quantify phosphates, nitrates, metals and toxins in groundwater or analyse human body fluids.

At the moment, MicroParts produces the spectrometers for visible and mid-infrared wavelengths. A near-infrared unit is being developed, as are prototype sensors for the detection of gases like butane, propane, methane and CO(2).

In operation, optical fibre channels guide incident light into the spectrometer. A blazed diffraction grating splits the light into its constituent wavelengths and focuses these components along a photodiode array.

The key to making the spectrometer accessible to mass markets, however, lies in the manufacturing technology. MicroParts developed a microstructuring technique which starts with deep X-ray lithography in which synchrotron radiation exposes a photosensitive resist through a special mask. Organic solvents then develop the exposed areas to produce a plastic template which is filled with metal in an electroforming bath.

After the plastic has been stripped, the metal is polished and fitted to an injection moulding machine. This then becomes the master mould for the final device.

Photonics and Analytical Marketing is the distributor of the spectrometer in the UK. The spectrometer is available with a complete evaluation kit for design engineers, including a computer interface and software, as well as many accessories that include light sources, cuvettes and flow cells.

Photonics and Analytical Marketing

Tel: Leeds (01132) 931985

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