: Microcantilevers, one of the most common MEMS structures, have been introduced as a novel sensing paradigm nearly a decade ago. Ever since, the technology has emerged to find important applications in chemical, biological and physical sensing areas. Today the technology stands at the verge of providing the next generation of sophisticated sensors (such as artificial nose, artificial tongue) with extremely high sensitivity and miniature size. The article provides an overview of the modes of detection, theory behind the transduction mechanisms, materials employed as active layers, and some of the important applications. Emphasizing the material design aspects, the review underscores the most important findings, current trends, key challenges and future directions of the microcantilever based sensor technology.

Bimaterial Microcantilevers as a Hybrid Sensing Platform

The paper pr esents analyses of current research projects connected with explosive material sensors. Sensors are desc ribed assigned to X andrad iation, optical radiation sensors, as well as detectors applied in gas chromatography, electrochemical and chemical sensors. Furthermore, neutron techniques and magnetic resonance devices were analyzed. Special attention was drawn to optoelectronic sensors of explosive devices. Keyw ords: Explosive device sensors, detection of explosive materials.

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Sensors and Systems for the Detection of Explosive Devices - An Overview

The damping effect in the nanoscale mechanical beam resonators operated under ambient conditions was studied. Experimental measurement of the viscous air damping in the nanowire cantilever resonators was carried out using the electric-field-induced resonance method; and a theoretical model, which accounts for the effects of dimension and material property of the nanowires and the air viscosity of the environment, was developed for describing the mechanical resonance and damping. The study showed that the damping effect in the nanoscale beam resonators operated in air could be as high as that in the microscale resonators operated in liquids, and scaled with the geometric dimension of the studied nanowire cantilevers.

Experimental measurement and model analysis of damping effect in nanoscale mechanical beam resonators in air

An urgent need exists for the development of inexpensive, highly selective, and extremely sensitive sensors to help combat terrorism. If such sensors can be made miniature, they could be deployed in virtually any situation. Terrorists have a wide variety of potential agents and delivery means to choose from for chemical, biological, radiological, or explosive attacks. Detecting terrorist weapons has become a complex and expensive endeavor, because a multitude of sensor platforms is currently needed to detect the various types of threats. The ability to mass produce and cost effectively deploy a single type of sensor that can detect a wide range of threats is essential in winning the war on terrorism. Silicon-based microelectromechanical sensors (MEMS) represent an ideal sensor platform for combating terrorism because these miniature sensors are inexpensive and can be deployed almost anywhere. Recently, the high sensitivity of MEMS-based microcantilever sensors has been demonstrated in the detection of a variety of threats. Therefore, the critical requirements for a single, miniature sensor platform have been met and the realization of an integrated, widely deployable MEMS sensor could be near.

Moore's law in homeland defense: an integrated sensor platform based on silicon microcantilevers

Analyte species and concentration identification using differentially functionalized microcantilever arrays and artificial neural networks

We report on the performance of a measurement system for the recognition of individual analytes and their binary mixtures which is based on a multiarray of four micromachined silicon cantivelers actuated at their resonance frequency. The cantilevers have been functionalized by organic polymers [polydimethylsiloxane (PDMS) and polyvinylpyridine (PVP)] and amorphous nitrogen-rich carbon nitride films. We found that the sensitivity and selectivity of the cantilevers coated with CNx films change according to the layer thickness. Our results show that the selected combination of sensitive layers ensures a wide range of specific, reversible and reproducible sensor responses upon exposure to methanol, 2-propanol, water and their binary mixtures. Further, it was found that the differences in recovery times of PDMS and CNx films after exposure to the two alcohols and their mixtures could be used especially for low analyte concentrations as a second characteristic in addition to the resonance frequency shift for th...

Chemical recognition based on micromachined silicon cantilever array

This paper summarizes our achievements in the development of an advanced microcantilever-based platform for the detection and recognition of various volatile analytes. The implemented microcantilevers include integrated piezoresistive readout, integrated thermally driven bimorph actuator, and a gold pad at the cantilever apex for functionalization toward the detection of specific substances. Up to eight single microcantilevers can be installed and investigated quasisimultaneously in either gas flow or gas/vapor single injection mode. The experimental setup enables the detection of the microcantilever bending via surface stress changes, characterization of either amplitude or phase spectra of the microcantilever, and also calibration of its sensitivity.

Experimental setup for characterization of self-actuated microcantilevers with piezoresistive readout for chemical recognition of volatile substances.

Nanoparticle metal films functionalized with calixarenes offer a novel technology for highly effective, technologically feasible, small and cheap chemical gas sensors. We have designed, manufactured and measured the performance of chemical gas sensor elements, where molecular absorption by the calixarene layer controls the electrical conductivity of a nanoparticle gold film evaporated on a dielectric substrate. The sensors were exposed to several alcohol and water vapors and the dynamic sensor responses were analyzed. Resistance variation of the measured samples achieves 10%. Current-voltage curves, recovery characteristics and temperature dependencies of the sensor elements were investigated. Degradation of the sensitivity due to the aging effect was observed. We show that differences in the sensor recovery time, as well as concavity or convexity of the leading edge of the sensor transition curve could be used as additional information parameters for chemical recognition system.

http://ieeexplore.ieee.org/iel5/9624/30805/01426255.pdf

Calixarene-coated nanoparticle gold films for chemical recognition system

Der Artikel beschreibt die Realisierung von piezoresistiven Cantilever-Arrays für die Raster-Kraft-Mikroskopie. Sensoren für die Raster-Sonden-Mikroskopie (RSM) sind aus physikalischer Sicht faszinierende Mikrosysteme, da sie durch geeignete Kombination von Physik und Technologie ein neues nanoskopisches Materialverständnis ermöglichen. Die Raster-Sonden-Mikroskopie führt nicht nur zur Eröffnung neuer Horizonte für die Grundlagenforschung, sondern bietet auch die Chance, durch die Entwicklung neuartiger Sensoren und Sensorarrays bisher ungenutzte Wirkmechanismen zu nutzen. Physikalische, biologische und chemische Größen und Wechselwirkungen können auf der Basis von Mikro-Biegebalken (sog. Cantilever) durch die Umwandlung in eine mechanische Reaktion (Verbiegung des Cantilevers) sehr effektiv erfasst und dann wiederum in elektronisch verwertbare Signale umgewandelt werden. In diesem Artikel werden die Grundideen zur Realisierung von selbstoszillierenden piezoresistiven Cantilever-Arrays als System vorgestellt, mit denen Bilder mit hoher Geschwindigkeit aufgenommen werden können. This paper reports on to the realization of piezoresistive cantilever-Arrays used in scanning probe microscopy (SPM). Sensors for the SPM are peculiar microsystems since the combination of physical and microtechnological principles allows to gain an insight into the material science at nanoscale. Moreover SPM technology is opening new horizons in fundamental research and gives a chance to employ new interaction principles for the realization of new sensors and sensor arrays. Physical, biological, and chemical values and interactions can effectively be detected and analyzed using cantilevers, where the nanomechanical interactions can be transformed into an electric signal. The basic issues for the realization of a complete system of self-actuated, piezoresistive cantilever arrays are described.

Raster-Sonden-Mikroskopie mit Cantilever-Arrays (Scanning Probe Microscopy with Cantilever Arrays)

NANOJET (Nanonozzle Plasma Jet Microfabrication Technology) based on scanning micro/nano-nozzle is a competitive candidate for high-resolution direct nano-structuring of different materials. In this device, electrically neutral radicals created in plasma discharge are transported through a small tapered capillary (or nozzle). A short distance between the nozzle and treated surface allows the localized chemical interaction. A description of free radicals transport through a high aspect ratio hollow tip and localized etching and high etching rates without ion bombardment are demonstrated in this work. A Monte Carlo (MC) based simulation model is used to study the transport and kinetic properties of atomic oxygen gas flow through the finite length cylindrical nozzle with different aspect ratios. The general aim of these investigations is to determine and optimize the radicals transport and optimal etching capability. The MC-simulations are compared with detailed experimental measurements, carried out for different nozzle sizes, etching rates, and distances between the nozzle outlet and the sample. To explore the influence of the oxygen gas flow kinetic properties on the etching parameters, the oxygen atoms transmission is simulated for a variety of the nozzle aspect ratios. This article presents the fundamental considerations and the experimental proofs of the outlined nanofabrication technique.

D. Filenko

Papers

Chemical recognition based on micromachined silicon cantilever array

Experimental setup for characterization of self-actuated microcantilevers with piezoresistive readout for chemical recognition of volatile substances.

Calixarene-coated nanoparticle gold films for chemical recognition system

Raster-Sonden-Mikroskopie mit Cantilever-Arrays (Scanning Probe Microscopy with Cantilever Arrays)

Radicals transport modelling in NANOJET