Year
2012
Abstract
Piezoresistive microcantilever sensors in which the microcantilever is partially embedded into the sensing material have been referred to as embedded piezoresistive microcantilever (EPM) sensors [1]. These EPM sensors operate by embedding or partially embedding a small piezoresistive microcantilever into a “sensing material”. The sensing material is synthesized in such a way as to respond volumetrically to the presence of a particular analyte species. In many cases, chemical, physical or other reactions with the sensor material may produce the desired volumetric shift. Sensing materials used in EPM applications may include common organic polymers, composite polymer/biomolecule materials, or polymers functionalized with other active particles or chemicals. When they are exposed to the analyte species, the sensing material volume change causes a bending or strain the embedded cantilever, which is subsequently measured as a resistance change by the sensor electronics. Volume changes in the sensing material may be due to diffusion of the analyte molecules into the sensing material, probe-target binding on the material surface or bulk, or surface or bulk chemical reactions between the analyte and sensing material. In many cases, only tiny volumetric changes are needed to successfully detect the target species, as microcantilever strains of only a few angstroms are measurable. Electronics for these sensors is generally simple and inexpensive, as only the resistance of the microcantilever is measured. Previously, these types of sensors have been used to detect volatile organic compounds [1], bacteria in solution [3], viruses [4, 5], carbon monoxide [6], cyanide [7], hydrogen fluoride, and other analytes.