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Mechanics gets sensitive

Tiny mechanical sensors being developed in the Nanoscale Science Laboratory can be used for applications as diverse as testing the performance of turbines, the purity of drinking water and the presence of cholesterol in the blood. These sensors, based on the deflection of a cantilever, have been developed using conventional silicon processing technology, which means they can be incorporated into conventional integrated circuits for a variety of applications. They can be produced to detect minute alterations in chemical, thermal, stress or mass loading or in magnetic signals.

sem photo of fly's eye with sensor

A sensor, 100µm long, shown in front of a fly's eye, for scale.

Professor Mark Welland explains: "These structures are about 100µm x 10µm in size, and less than 1µm in thickness. We can sensitise one side of them so that when a gas, chemical or even a particular protein passes over the surface, the structure is caused to bend. It behaves just like a very small mechanical beam. Using a laser of the type found in a CD player, we can detect the movement of the beam, which may be as small as only one atomic displacement, making this type of sensor extremely sensitive.

The small scale of these sensors means that up to around 50 different types of sensor can be packed on to a silicon chip only about 1mm2, all measuring and reporting on different things. The chips can then be incorporated into existing electronic technology such as computers or white goods such as fridges and washing machines.

This type of sensor is ideal for picking up small changes in pressure and velocity of the gases flowing in a working turbine, which provides crucial information for the designers. We are working on these in conjunction with researchers from the Aeronautics' laboratory; Drs Holger Babinsky and Howard Hodson" explains Mark Welland. "Ultimately smart sensors based on this technology will be built in to all sorts of things. They can be used to monitor the correct amount of detergent to be put in to a washing machine or the emissions given off from food in a refrigerator which will signal when it should be used. Alternatively, a smart sensor incorporated into a computer could monitor the breath of the operator for tell tale signs of say, when a diabetes sufferer should take an insulin dose."

The latest breakthrough has been the development of this type of sensor to work in a liquid environment, opening up new application areas, particularly in the pharmaceutical industry. For instance, the accurate detection of particular protein types can be used for monitoring harmful cholesterol levels, pregnancy testing or the levels of oestrogen in drinking water. This work is being carried out in conjunction with the Department of Chemistry, and pharmaceutical applications are being developed with funding from AEA Technology.

For further information, please contact Professor Mark Welland on 01223 332676, e-mail: mew10@eng.cam.ac.uk
Web site: http://www2.eng.cam.ac.uk/~nano-www/

number 9, July 2000 home | contents | previous | next