We have used embedded piezoresistive microcantilever (EPM) sensors in the detection of volatile organic compounds, industrial chemicals, and biological molecules. The EPM design incorporates a tiny piezoresistive microcantilever embedded or partially embedded into a material sensing layer. The sensing layer material is chosen so as to react to the desired analyte(s), and undergo a minute volumetric or vertical shift in dimension. In the present paper, we present results on the sensing of various VOC's, vaccinia virus in solution, carbon tetrachloride in vapor, and osmolality in human subjects.

The effect of dopants on the band structure and crystal structure of Ba0.5Sr0.5TiO3thin films on (100) LaAlO3 substrates has been investigated. The dopants include Ti, Mg and Al. The band-gap energies of the thin films were determined from the transmission spectra measured by UVVIS spectrophotometer and increased with the increase of dopant concentration regardless of the type of dopants. The crystal structure was studied by using transmission electron microscopy, atomic force microscopy, x-ray diffraction and micro-Raman spectroscopy. The relation between band structure and crystal structure was discussed.

In order to extend the dynamic range of a hydrogen sensor with a metal-insulator-semiconductor (MIS) type structure, Pd-Cr and Pd-Ni alloy gated samples were studied. The PdCr gated sample shows quite stable and reproducible response, and could measure hydrogen concentrations from 100 to 50, 000 ppm. While the Pd-Ni gated sample shows turn-on/off response drift, this drift is probably due to the presence of oxygen on the surface of the insulator and the formation of metal hydride. Furthermore, the effect of oxygen on the sensors response was investigated; oxygen may deplete protons from the metal/insulator interface and could reduce the sensor's response.

The aim of this work is the structural and sensing characterization of titanium-doped gamma iron oxide nanocomposites. These nanopowder materials were synthesized by the laser pyrolysis technique. It is based on the resonance between the emission of a CW CO2 laser line and the infrared absorption band of a gas (vapour) precursor. Basically, sensitised iron pentacarbonyl and titanium tetrachloride-based mixtures were used as gas-phase reactants. The compositional characterization of the synthesized nanostructures was performed by means of different analytical techniques. Introducing Ti in the Fe2O3 network in small quantities (< 1 %) seems to have little influence on titanium doped powder morphology (mean grain size ∼ 5nm) but increases the sensitivity of titanium doped iron oxide nanopowders with more then 20 % relatively to pure maghemite.

This paper describes the design, modeling, fabrication, and testing of electroplated metal electrostatic torsion micromirror arrays. The goal is to develop novel micromirror arrays optimized for high temperature operation for use in epitaxial growth systems such as MOCVD and MBE to define device structure and hence eliminate the need for etching and lithography. The metallic micromirror arrays were fabricated with a hexagonal shape and with diameters of 0.5 mm2 and 1mm2. The micromirror arrays were structurally composed of primarily electroplated nickel, a mechanically durable material with a high glass transition temperature and with controllable residual stress. The torsion beam was designed with a straight bar and serpentine shape in order to optimize the voltage necessary to tilt the micromirror by ± 10°. A finite element model built in Ansys has been employed to determine the micromirror geometries and performance. A voltage of 130 volts was required to rotate the mirror with a serpentine shape beams by 10°. In addition, the mirror was operated at a resonant frequency of 2.2 kHz.

This paper presents a novel method to create and integrate micro-machined devices and high aspect-ratio (height-to-width ratio) microstructures in which the microstructures are built up using multiple layers of photopolymer film and/or viscous solution. Very high aspect-ratio 2-and 3-dimensional (2-D and 3-D) microstructures were constructed by stacking photo-imageable polymer films. Such films may be dry films applied by lamination or solution layers applied by bar coating, or doctor blade coating. Photolithography is used in both cases to define the microstructure. This additive process of thin-film micromachining facilitates high aspect-ratio microstructure fabrication. We have demonstrated structures of up to 12-layers comprising 2-D arrays of deep trenches (180 μm deep and 25 μm wide) and a 2-layer SU-8 micro-trench array with an aspect ratio up to 36 on glass substrates. Miniaturized structures of interconnected reservoirs as small as 50 μm × 50 μm × 15 μm (∼38 pico liter storage capacity) are also being fabricated, along with a novel 5-layer microfluidic channel array and a vacuum-infiltration process for fluid manipulation. This method has the potential to create functional large-area micro-devices at low-cost and with increased device flexibility, durability, prototyping speed, and reduced process complexity for applications in optoelectronics, integrated detectors, and bio-devices. The novel multi-layer photopolymer dry film and solution process also allows microstructures in micro-electro-mechanical systems (MEMS) to be built with ease and provides the functionality of MEMS integration with electronic devices and integrated circuits (ICs).

In this paper we present a comprehensive study of the impact of the Hydrogen (H2) annealing conditions on nano scale silicon fin structures. Hydrogen pressure was varied from 15Torr to 600Torr and anneal temperature was varied from 600°C to 900°C. We found H2 annealing can cause faceting, corner rounding and smoothing of the etched silicon surfaces. The degree of the fin transformation is a function of both pressure and temperature. Furthermore, low pressure and high temperature enhance the silicon movement and can cause damage to the nano scale fins.

Recently, carbohydate-carbohydrate recognition has emerged as a new type of interaction in cell adhesion processes. One of these carbohydrates, the LewisX determinant (LeX), has been shown to be involved in murine embryogenesis. Here we confirm the existence of this specific interaction by measuring the adhesion between giant vesicles functionalised with synthetic Lex bearing lipids providing to the LeXdeterminent a high orientational freedom. This was obtained by micropipette aspiration and contact angle measurements. By using a simple model involving the several contributions to the adhesion free energy, specific and non specific interactions could be separated and quantified. In a second step, using natural Lex bearing sphingolipids, we could underscore the high sensitivity of LeX-LeX recognition to molecular structure and prove that the possible orientations provided by the natural LeX bearing molecules not only allow but strongly favor LeX-LeX recognition.

We developed an efficient method in achieving a wide range of high-quality ZnO nanostructures by zinc powder evaporation at lower temperature. The synthesis under specific conditions of ZnO nanostructures, such as comb-like structures, well-aligned nanorods, nanonails and core-shell ZnO/SiOx nanowires, were introduced in detailed respectively in this letter. Meanwhile, SEM, TEM, HRTEM and EDX investigations were performed on the products and revealed the crystal structure and the growth mechanism. These high-quality nanostructures enriched the family of ZnO nanomaterials and may have potential applications in optoelectronics, sensors and nanoscale mechanics research.

We present a new conceptual active optical microphone based on complementary metal-oxide semiconductor (CMOS) - micro electro mechanical systems (MEMS) micromachining techniques. The diaphragm of the microphone has a diffracting grating fabricated by the CMOS process with only a small number of post-processes. The active microphone actuates the diaphragm on an arbitrary frequency by electrostatic force, and detects sound waves by the light waves. From the verification experiment result, this active microphone was able to perform advanced functions, such as the amplifier effect and the detection of phase information of sound waves.

This paper reports on the fabrication of novel all-polymer microbridge electrostatic actuators based on conductive polymers and using surface micromachining on glass substrates. The electromechanical properties of the microbridges are studied using electrostatic actuation and optical and electrical detection. The pull-in phenomena and a dependence of the bridge deflection with the square of the applied voltage are observed. Compared to the silicon-based microbridges, the polymer structures present higher deflection amplitude for the same applied electrical force. The resonance frequency of the polymer bridges occurs in the MHz range and with quality factors of the order of 100 when measured in vacuum. The mechanical properties of the polymer device are affected by the residual stresses.

We characterize, experimentally and theoretically, the electronic properties of the S/Cu(001) interface in two molecule-metal systems, Mercaptobenzoxazole(MBO) and Methanethiol on Cu(001), containing the S-headgroup. The S atom realizes the anchoring of the whole molecule to the substrate through the formation of an S-Cu hybrid, irrespective of the p(2×2) and c(2×2) reconstruction, but with different relative orbital contributions. This behaviour may be highlighted only by the comparison of the high resolution angular resolved photoemission spectra with the ab inito calculated electronic density of states of the interface.

We present the fabrication and electromechanical characterization of a class of polymeric high-elongation strain sensors. Samples of polydimethylsiloxane were coated with Creative Materials, Inc.'s 123-27 Electrically Conductive Silicone Ink and the resistance behavior was evaluated in uniaxial tensile tests. Large strains (up to 100%) were observed with monotonically increasing resistance changes. A clear, linear trend up to 65% strain dominated the resistance vs. strain behavior then resistance increased non-linearly. Image processing of the film coupled with a finite element conduction simulation indicate the change in resistance is primarily a geometric effect. Both the conduction path and the polydimethylsiloxane substrate break completely around 100% strain. The samples exhibit a gauge factor of approximately 10.

Ultra-Fine ZnO nanobelts are grown via thermal evaporation and condensation method without the use of any catalyst on the substrates. These nanobelts have an average width of about 5.8 nm. Photoluminescence spectra reveal that there is a blue shift in the near band edge ultra violet emission from 381 nm to 367 nm equal to 124 meV. These ultra-fine nanobelts have been studied for size induced optical and electrical properties.

Integrated micrometer scale interpenetrating Au-Nanostructured TiO2 (NST) network nanocomposites have been fabricated using a two step process. First, NST pad arrays were prepared by reacting Ti surfaces, patterned with an SiO2 masking layer, with aqueous H2O2. NST formed is porous with pores 50 to 200 nm in diameter and walls about 75 to 125 nm thick. Second, Au was infiltrated into pores of NST using electroless deposition to form the nanocomposite. SEM studies indicate that Au was deposited into pores of NST with little void formation. Selective deposition of Au on NST pads was confirmed using XRD and area-mode XPS. This process is a general route to forming micrometer-scale nanocomposite features consisting of NST and metals that are amenable to electroless deposition.

Switches and relays that have emerged from the microelectromechanical systems (MEMS) technology have the potential to replace traditional solid-state devices due to broader operating temperature range, higher breakdown voltage, and much higher off-state resistance. Interest in MEMS switches and relays has surged recently, principally due to the demonstrated performance in switching radio-frequency signals. However, understanding of the effect of the surface topography on performance and lifetime of these microdevices is rather empirical. Therefore, the objective of this study was to explore the role of surface topography in various physical phenomena encountered at contact interfaces of MEMS switches and relays. Emphasis is given on the dependence of pull-in voltage, electric field, and electrical breakdown on surface topography and interpretation of contact interface phenomena associated with surface erosion and adhesion in the context of surface topography effects. In addition, current obstacles in the study of the influence of the surface topography on the performance of MEMS switches and relays are discussed in light of recent findings.

In this paper, we describe nanostructured substrates as suitable and functional platforms for neuron scaffolding. Neurons are electrically excitable mammalian cells that on network formation serve as conduits for information transfer. A vast amount of information is transferred through the cells in the spinal cord via synaptic and gap junctions in the electro-ionic fashion mediated by neutrotransmitters. Carbon nanotubes (CNT) are strong, flexible, conduct electrical current and they are biocompatible and non-biodegradable. They can be functionalized with different biomolecules like neuron growth factors and adhesion agents, properties that come useful in formation of neuron hybrids. These properties of the nanotubes make them potentially successful candidates to form prosthetic substrates to guide neurite outgrowth. A combination of microlithography and chemical vapor deposition is used to engineer patterned vertical multiwalled carbon nanotube substrates. These substrates function as scaffolds and are used to demonstrate the formation of directed neuronal networks. Multiple substrate geometries and nanotube heights are fabricated to determine the most suitable combination for understand the cell morphological changes. Changes in the interaction between the cell membrane and the nanotube substrate are visually characterized. Cell viability is determined via calcium staining and different types of nano-structure substrates are also tested for further studies.

The effects of temperature on micro heaters made of Ti/TiN stacks and pure TiN layers on bulk micromachined membranes have been studied. Ti/TiN stacks show a thermal stability up to 380°C, beyond that temperature an enhanced interaction within the stack and/or with adjacend layers leads to a degradation of the resistance. The pure TiN layers withstand temperatures up to 600 °C, this limitation is only given by the mechanical stability of the membran stack, which is destroyed beyond this temperature. These layers are suitable for sensors in which an elevated temperature provided by heating lines on a membran for thermal isolation and fast response is necessary for functionality.

Single-phase vanadium-dioxide (VO2) thin films have been deposited on various substrates by means of a reactive pulsed-laser-deposition technique. While the preferred orientation is (011) monoclinic for the films deposited on silicon substrates and (020) monoclinic for those deposited on sapphire substrates, the thermochromic properties of the VO2 layers is found to be fairly independent of the substrate type. It is further shown that W doping and Ti-W co-doping significantly improve the thermochromic properties. Following growth, VO2 layers were used in the context of the development of micro-switching devices. For this purpose, patterning of the VO2 layers was investigated using a high-density argon magnetoplasma. Highly anisotropic features have been produced with a high etch rate and a good selectivity over resist. The etch rate for VO2/Al2O3 samples is found to be higher than that for VO2/Si samples, which is due to the higher number of surface dangling bonds in the (020) phase as compared to the (011) phase.

Low pressure chemical vapor deposition (LPCVD) and plasma enhanced chemical vapor deposition (PECVD) silicon oxide and silicon nitride films were implanted subcutaneously in a rat model to study in vivo behavior of the films. Silicon chips coated with the films of interest were implanted for up to one year, and film thickness was evaluated by spectrophotometry and sectioning. Dissolution rates were estimated to be 0.33 nm/day for LPCVD silicon nitride, 2.0 nm/day for PECVD silicon nitride, and 3.5 nm/day for PECVD silicon oxide. A similar PECVD silicon oxide dissolution rate was observed on a silicon oxide / silicon nitride / silicon oxide stack that was sectioned by focused ion beam etching. These results provide a biostability reference for designing implantable microfabricated devices that feature exposed ceramic films.