A simple and efficient way of preparing highly sensitive SnO2 nanowire-based gas sensors without an arduous lithography process was studied. The network of SnO2 nanowires could be suspended upon the Si substrate by separating the Au catalyst layer from the substrate. As the electric current is transported along the networks of the nanowires, not along the bottom layer on the substrate, the sensitivity to gases was maximized in the suspended and networked structures. The sensitivities were 18 and 180 when the NO2 concentrations were 0.5 and 5 ppm. The response time was typically 20-50 s.

The application of vascular stents using conventional metals is limited because the implantation process will cause significant injury to the vascular wall and endothelium, resulting in neointima hyperplasia and then the development of long-term restenosis. The objective of this in vitro study was to investigate endothelial cell function (especially their adhesion behavior) on highly controllable nanostructured surface features. Considering the importance of the endothelium and its properties, highly controllable nanostructured surface features of titanium (a popular vascular stent metal) were created using E-beam evaporation to promote endothelialization and to control the direction of endothelial cells on vascular stents. Endothelial cells are aligned with blood flow naturally in the body. In this manner, the present in vitro study provides much promise for the use of nanotechnology for improving metals for vascular stent applications.

Rare-earth doped yttrium oxide nano-particles modified with bio functional polymers are one of the good candidate for upconversion bio imager. The requirement to the particles for bio imaging application is a small particle size less than 50 nm, dispersion and chemical durability in body fluid. In this study, polyacrylic acid (PAAc) was used for both precursor precipitation and surface modification of the calcinated particles. The use of the PAAc resulted in small particle size at 33 nm. Also, the modification by adding 104 PAAc/particle resulted in chemical durability and dispersion of the particles under heavily acidic and basic conditions.

In this paper we demonstrate a gas-phase process to fabricate Ag nanoparticles-based bio-sensing devices. Ag nanoparticles, prepared from the gas phase through spray pyrolysis, are size-selected via electrostatic classification. These size-selected nanoparticles are then successfully attracted and aligned onto an electrostatic-patterned biased P-N junction substrate to form high- resolution nanoparticle patterns. Particles in the size range of 30-100 nm were evaluated. Our approach provides a promising tool for precise assembly of nanoparticles for future device applications.

Aluminum wires are electrochemically sculptured into bi-directional templates for the growth and contacting of nanowires as three terminal devices. The utility of this nanostructured micro-template is demonstrated by a ZnO nanowire surrounding gate field-effect transistor. This bottom-up approach to a 3-D nanowire transistor is unique in that it can be almost entirely fabricated in a beaker using aqueous, room-temperature electrochemistry.

A passive chemiresistor micro-sensor was investigated for the detection of hydrazine compounds. Hydrazine compounds are a highly toxic and carcinogenic species exhibiting toxic effects in humans at very low levels of exposure. Therefore, a sensor capable of detecting ppb levels of hydrazine compounds is required to insure the safety of personnel. The present study describes the fabrication, testing, and characterization of a low-cost, ultrasensitive Poly (3-Hexylthiophene) (P3HT) thin film-based micro-sensor for the detection of hydrazine compounds. Standard microelectronic manufacturing techniques were used to form a micro-sensor composed of a silicon substrate, interdigitated gold electrodes, and P3HT sensing film. Responses of the micro-sensor to hydrazine compounds at different temperatures and concentration levels are reported. When exposed to 25 ppm hydrazine in nitrogen, the sensor's resistance was measured to change from a few ohms to over 10 Megaohms. The thermal stability of the P3HT micro-sensor and the method to improve thermal stability are also explored. Thermally annealing the P3HT micro-sensor was found to improve thermal stability at high temperatures. Moreover, the sensor exhibits good specificity to hydrazine and does not respond to the presence of NO2 and/or N2O.

We demonstrate a highly sensitive potentiometric gas sensor based on a resonating Si microcantilever. Using a scanning probe microscope based set up in non-contact mode, the microcantilever was made to oscillate at its resonance frequency with periodically changing amplitude, using simultaneous mechanical and electrical excitation sources. The variation of the oscillation amplitude was found to be extremely sensitive to changes in surface potential, and served as a linear indicator for surface work function changes caused by molecular adsorption. The microcantilever sensor was found to be able to detect changes in surface potential down to 50 microvolt, which is basically limited by the system noise. When applied to sensing hydrogen using platinum coated cantilevers, it was observed that the microcantilever sensor can detect 1000 ppm hydrogen with an estimated lower limit of the detection time of 70 ms, at a cantilever-ground electrode distance of ∼10 micron. Several parameters, such as ac signal amplitude, cantilever – reference electrode distance, quality factor, area, and spring constant of the cantilever, can be adjusted to significantly enhance the sensitivity, possibly by orders of magnitude. Excitation of the cantilever at subharmonic resonance frequencies was also performed to study possible parametric resonance effects. In this system it was possible to observe sub-harmonic resonance of order more than 50 (i.e. lower than one-fiftieth the resonance frequency).

We present functional patterns fabricated using functional polymers. The functional polymer is MIP (molecularly imprinted polymer) system, which can be produced through “molecular imprinting” to create “synthetic receptor or binding sites” for bio/chemical detection technology. Those binding sites have specific molecular recognition functions for targeting organic or bio molecules. MIP's patterns in the micro-scale were fabricated for chemical sensors, diagonostic bio-sensors, and for drug delivery systems. We also obtained homogeneous MIP's micro-particles, which have high affinity receptor sites only using a microfluidic reactor.

Polymer/SWN nanocomposites were synthesized in the soap-free emulsion polymerization of methyl methacrylate (MMA) using 2-hydroxylethyl methacrylate (HEMA). The SWN in the polymer/SWN nanocomposites was individually dispersed in water, and these are adsorbed on the surface of monomer droplets. Polymer/SWN nanocomposites were obtained by adding an aqueous dispersion of layered silicate to the polymer emulsion. X-ray diffraction (XRD) and FT-IR spectra were utilized to characterize the structures of the nanocomposites. The degree of dispersion of these nanocomposites was investigated by transmission electron microscopy (TEM). Furthermore, the thermal and mechanical properties of polymer/SWN nanocomposites were determined using thermogravimetric analysis (TGA), differential scanning calorimeter (DSC) and dynamic mechanical analysis (DMA). The increased tanδ of the obtained nanocomposites is caused by the fine dispersion of SWN particles into the polymer matri

Despite their diverse application potential, carbon nanotubes (CNT) have adverse effects in vitro, and in vivo. Previous research has focused on the in vitro cytotoxic impact of CNT aggregates and associated nanoparticulate impurities. In this study, we compared the single-walled carbon nanotube (SWNT) aggregates, and their associated finely dispersed, non-aggregated carbon nanomaterials on rat aortic smooth muscle cells (SMC), through filtration of the aggregates from the CNT-treated cell culture media. In general, our research shows that the removal of single-walled carbon nanotube (SWNT) aggregates from cell culture test media inhibited the growth in SMC to a lower extent than the corresponding unfiltered media at pre-filtered SWNT dosages below 0.10 mg/ml. We also found suspended nanoparticles (likely amorphous and graphitic carbon associated with the SWNT) and a small quantity of SWNT in the filtered media may have contributed to the observed cell growth inhibition by the filtered media. In addition, we compared the effect of SWNT, a nano-sized material, with activated carbon (AC), a nanoporous, microparticulate material, on SMC growth. AC (0.1 mg/ml) was found to be less inhibitory to SMC growth than the SWNT aggregates and suspended matter (0.1 mg/ml), potentially implying an inverse proportionality between carbon nanomaterial size regimes and cell growth inhibition.

Contrary to the conventional use of semi-conductive metal oxides as gas detectors for components in air the analytical performance of segmented SnO2-layers were investigated to detect and discriminate impurities in inert gases such as nitrogen or helium. A broad variety of technical processes require high purity inert gases which have to be kept under permanent surveillance to detect leaks to the atmosphere, a gas release of contaminated fittings or other contaminations. The unique gradient gas sensor microarray of the Karlsruhe micronose (KAMINA) was equipped with segmented layers of either nanoparticle or sputtered SnO2 layers and exposed to a high purity nitrogen flow of 1lit/min into which temporarily model impurities have been admitted with a variety of concentrations. Pulsed exposures were performed to nitrogen containing oxygen (0.2 to 10 vol %), water vapour (5 to 15 % relative humidity) and 2-propanol as well as tetrachloromethane in the ppm range. For all model contaminations a fast and sensitive response has been found. The measured concentration dependence revealed a detection limit of about 0.01 vol% for oxygen and 0.03% of relative humidity for an operating temperature of the KAMINA chip at 325..273 °C. The detection limits for the organic compounds were even found to be in the lower ppb range. The conductivity patterns obtained from the simple segmentation microstructure of the KAMINA SnO2 layers operated with a temperature gradient were evaluated by a Principal Component Analysis (PCA) which proved an appropriate gas discrimination power to distinguish pure nitrogen and the different kinds of contaminations for both types of SnO2 layers. However, the sputtered layer showed better detection limits while the nanoparticle layers offered a better sensitivity, i.e. a higher slope of the concentration dependence.