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MEMS interferometric sensor boasts sensitivity at -1?N/m

Posted: 05 Mar 2014 ?? ?Print Version ?Bookmark and Share

Keywords:sensor? MEMS? interferometer?

MEMS-based sensors suffering from poor sensitivity has prompted a team of researchers from the Toyohashi University of Technology to develop a label-free biosensor, the sensitivity of which is claimed to have boosted by a factor of 100.

Conventional sensors used in medical applications detect molecules by measuring the deflection of cantilevers cause by biololecular adsorption. It is said that the low conversion of linear transducing from the mechanical deflection to the readout signal makes for the sensor's poor sensitivity.

In addressing this weakness, the researchers applied a Fabry-Perot interferometer. The device was integrated with a photodiode which utilises the non-linear optical transmittance change, enhancing the sensitivity.

Led by Kazuhiro Takahashi, the researchers predicted the theoretical minimum detectable surface stress of the proposed sensor at -1?N/m, two orders of magnitude greater than that of the conventional MEMS sensor.

The sensor was fabricated using a 4in p-type silicon wafer. The photodiode was integrated into the silicon substrate using ion implantation of phosphorus. Sacrificial polysilicon was isotropically etched to form a freestanding membrane. Amino-methyl-functionalised parylene was coated on the membrane for immobilisation of the biomolecules via electrostatic coupling.

The MEMS FabryCPerot interferometric sensor allows the use of a universal biochemical sensing platform in a label-free manner, the research team claimed.

- Christoph Hammerschmidt
??EE Times Europe

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