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The use of microfabricated cantilevers as bioaffinity sensors was investigated. Since many bioaffinity interactions involve proteins as receptors, we conducted studies of the magnitude, kinetics, and reversibility of surface stresses caused when common proteins interact with microcantilevers (MCs) with nanostructured (roughened) gold surfaces on one side. Exposure of nanostructured, unfunctionalized MCs to the proteins immunoglobulin G and bovine serum albumin (BSA) resulted in reversible large tensile stresses, whereas MCs with smooth gold surfaces on one side produced reversible responses that were considerably smaller and compressive. The response magnitude for nanostructured MCs exposed to BSA is shown to be concentration dependent, and linear calibration over the range of 1-200 mg/L is demonstrated. Stable, reusable protein bioaffinity phases based on unique enantioselective antibodies are created by covalently linking monoclonal antibodies to nanostructured MC surfaces. The direct (label-free) stereoselective detection of trace amounts of an important class of chiral analytes, the a-amino acids, was achieved based on immunomechanical responses involving nanoscale bending of the cantilever. The temporal response of the cantilever ([DELTA] deflection/[DELTA] time) is linearly proportional to the analyte concentration and allows the quantitative determination of enantiomeric purity up to an enantiomeric excess of 99.8%. To our knowledge, this is the first demonstration of chiral discrimination using highly scalable microelectromechanical systems.

The design, fabrication, and characterization of arrays of uncooled infrared and terahertz micromechanical detectors that utilize Si[O.sub.2] as a main structural material is described. The high thermal responsivities have indicated that the implemented devices could lead to an infrared imaging system with improved performance.

It has recently been shown that bimaterial microcantilevers can be used as uncooled infrared detectors. Bimaterial microcantilevers deform as their temperature changes due to the absorption of infrared photons. Infrared imaging using uncooled cantilever arrays has already been achieved by a number of groups. In this paper, we examined the performance of microcantilevers as uncooled infrared detectors with optical readout. As in the case of other kinds of uncooled thermal infrared detectors, temperature fluctuation noise and background fluctuation noise are fundamental limits to the performance of microcantilever thermal detectors. Since microcantilevers are mechanical devices, thermo-mechanical noise will also influence their performance. We fabricated a SiN[sub x] microcantilever thermal detector with an Al layer in the bimaterial region. For the microcantilever geometry and materials used, the background fluctuation noise equivalent temperature difference, NETD[sub BF], calculated for f/1 optics and a 30 Hz frame rate was found to be 1.26 mK. The NETD[sub TF], limited by temperature fluctuation noise, was calculated to be 7.4 mK while the thermo-mechanical NETD[sub TM] was calculated to be 5.3 mK. The sum of all fundamental noise sources, including the intrinsic noise of the “optical lever” readout, results in a total NETD of 9.2 mK. Absence of the readout noise would improve this parameter by only 2%. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Focuses on the improvement of the parameters of a nitrogen oxide sensor through conductivity modulation. Conductivity and thermostability of the sensor; Response time; Sensor sensitivity.