Saturday, 20 September 2014
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Electronics have a 'nose' for gas detection

A method of creating sensing elements for ‘electronic nose’ systems could pave the way for lower-cost and more efficient gas-detection systems in the food and medical industry.

Researchers at the Holst Centre in Belguim and Imec in the Netherlands are using ink-jet printing techniques to create polymer-coated microbridges that can detect parts per million (ppm) concentration levels of chemicals in the air.

Currently, sensors such as these are made from quartz crystals or chemi-resistors but their low power efficiency makes them unsuitable for portable electronic systems. ‘Our objective in the end is to make energy autonomous systems that you could integrate into a mobile phone,’ said Sywert Brongersma, project leader.

The microbridges are embedded with piezoelectric ‘shakers’ in a high-density array, which cause them to vibrate individually when they come into contact with chemicals in the air. Changes in their modes of vibration are a sign of changes in vapour absorption in their coatings and an indicator of the presence of the targeted chemical.

Scanning electron microscope image of a complete sensor chip (9mm x 9mm) consisting of 160 unique individually addressable micromechanical resonators

Scanning electron microscope image of a complete sensor chip (9 x 9mm) consisting of 160 unique individually addressable micromechanical resonators

The researchers claim that the high length-to-thickness ratio of the microbridges means that the gas sensor chip has a high sensitivity to low-concentration vapours. Integration of piezoelectric read-out schemes also makes it low in power consumption (less than 1mW per bridge).

‘You can target many applications with this,’ said Mercedes Crego-Calama, project co-leader. ‘For instance, at the moment we’re looking at wine and cheese monitoring, but in the future it can be used for things such as smart food packaging or the detection of human diseases.’

Work is currently focusing on carrying out simultaneous measurements from different array structures. Brongersma believes this will be completed in the coming months and hopes to have several prototypes ready by the end of the year.


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