Fabrication and characterization of annular thickness mode piezoelectric micro ultrasonic transducers

Micromachining techniques, in combination with low temperature ceramic composite sol-gel processing, have been used to fabricate annular array thickness-mode piezoelectric micro ultrasonic transducers (Tm-pMUTs). The processing techniques of low temperature (710 degrees C) composite sol-gel ceramic (sol + ceramic powder) deposition and wet etching were used to deposit and structure 27-microm thick lead zirconate titanate (PZT) films on silicon substrates to produce annular array Tm-pMUTs. Using these techniques, high quality PZT materials with near bulk permittivity have been obtained. The Tm-pMUT devices were shown to resonate at approximately 60 MHz in air and 50 MHz in water. From resonance measurements k(t) values ranging between 0.2 and 0.47 have been calculated and shown to depend on the level of porosity within the film. Lower values of kt were observed for films with higher levels of porosity, which was attributed to the relative decrease in the effective piezoelectric coefficient epsilon(33) with respect to stiffness and permittivity as a function of increasing porosity. This paper presents the successful micro-fabrication of a Tm-pMUT device and discusses the optimization of the poling conditions and effect of PZT microstructure on the coupling coefficient k(t). Pulse echo measurements in water, showing a -6 dB center frequency of 53 MHz and 47% -6 dB bandwidth, using a target 15 mm away from the transducer, have been included to demonstrate successful operation of the device. Full analysis of these results will be conducted in later publications.     

Effect of baffles on nitrification in aerated facultative lagoons in a cold climate.

Tracer studies performed in two aerated facultative lagoons indicate some bypass and an overall hydraulic regime close to completely-mixed. Results were used to calibrate a hydraulic model based on the tanks-in-series approach. The hydraulic model was combined with a simple "death-regeneration" biokinetic model to simulate seasonal nitrification as observed over a three year period. Modifications were made to the hydraulic model to represent the effect of baffle installations to 1) eliminate bypass and 2) impose a plug-flow regime. Simulation results indicate there is some gain to eliminating bypass but that imposing a plug-flow regime would increase biomass washout rates and hinder nitrification.     

Preparation of 5‐Membered Rings via Radical Addition‐ Translocation‐Cyclization (RATC) Processes Mediated by Diethyl Thiophosphites

A practical method for the formation of thiophosphonates bearing functionalized monocyclic, fused bicyclic and spirocyclic residues is presented. The procedure requires the easily available terminal alkynes as starting materials as well as commercially and readily available reagents such as diethyl thiophosphite. The experimental procedure consists of a one‐pot process without any slow addition of one of the reagents.     

Optical modeling of organic solar cells based on CuPc and C60

We have investigated the influence of the poly(3,4-ethylenedioxythiophene)-blend-poly(styrene-sulfonate) (PEDOT:PSS) layer on the short-circuit current density (J(sc)) of single planar heterojunction organic solar cells based on a copper phthalocyanine (CuPc)-buckminsterfullerene (C(60)) active layer. Complete optical and electrical modeling of the cell has been performed taking into account optical interferences and exciton diffusion. Comparison of experimental and simulated external quantum efficiency has allowed us to estimate the exciton diffusion length to be 37 nm for the CuPc and 19 nm for the C(60). The dependence of short-circuit current densities versus the thickness of the PEDOT:PSS layer is analyzed and compared with experimental data. It is found that the variation in short-circuit current densities could be explained by optical interferences.     

Novozym 435-catalyzed synthesis of polyetheramides from amino-esters,or diesters and diamines built on ethylene- and diethylene- glycol moieties

The optimization of CAL-B-promoted (Novozym 435) A/B and AA/BB type polymerizations leading to polyetheramides, from amino ethylesters or diethyl esters and diamines based on ethylene- or diethylene-glycol moieties, is disclosed herein. From these preliminary experiments it became obvious that it is of prime importance: to avoid the presence of water by carefully drying the enzyme prior to use; to eliminate ethanol from the reaction medium, by working under reduced pressure in order to drive the amidation reaction forward; to select an appropriate high boiling solvent, the best choice being diphenyl ether. Under such experimental conditions, polyetheramides were obtained in 70–80% yield with an average degree of polymerization (DPn) up to 17.     

Leachability and termite resistance of wood treated with a new preservative: ammonium borate oleate

Synthesis of a new chemical compound combining water-repellence of oleic acid and biocidal effect of boric acid linked by ammonia have been followed and validated by fourier transformed infra red (FTIR). This compound named ammonium borate oleate (ABO) has then been studied as a wood preservative. Different molar ratios of oleic acid have been involved in the synthesis of ABO and leachability of those mixes from wood observed according to Japanese industrial standard. The formulation one mole of boric acid and one of ammonia (1:1:4) for four moles of oleic acid has shown the best efficiency compared to formulations 1:1:1, 1:1:2 and 1:1:3 with about 52% of boron remaining after weathering when other formulations retained respectively 10%, 29% and 46% of boron in the case of an impregnation of Cryptomeria japonica. Seven solutions of 1:1:4 ABO in ethanol of different concentrations were then produced and sapwood blocks of C. japonica and Fagus crenata were impregnated. A toxicity threshold of around 2.0 kg/m³ for both species was determined in a termite resistance test to Coptotermes formosanus indicating the positive effect of combining water repellent and biocide. Termite mortality recording and microscopic observations complete this study indicating that the action mechanism of ABO is providing a water resistant inner coating.     

Design for mass customization: Product variety vs. process variety

Mass customization (MC) has become a reality and cannot be neglected as one of the leading strategies in satisfying customers and assuring companies survival in today's markets. MC can be offered either via product variability or process variability. How this is achieved using both approaches is the main core of this article. After an overview of related works, the influence of design variability on the overall generated value of the product is studied via a metric approach. A case study of the shoe industry is also presented, based on the experience of a European project called Dorothy.     

Dielectrophoresis‐Assisted Integration of 1024 Carbon Nanotube Sensors into a CMOS Microsystem

Carbon‐nanotube (CNT)‐based sensors offer the potential to detect single‐molecule events and picomolar analyte concentrations. An important step toward applications of such nanosensors is their integration in large arrays. The availability of large arrays would enable multiplexed and parallel sensing, and the simultaneously obtained sensor signals would facilitate statistical analysis. A reliable method to fabricate an array of 1024 CNT‐based sensors on a fully processed complementary‐metal‐oxide‐semiconductor microsystem is presented. A high‐yield process for the deposition of CNTs from a suspension by means of liquid‐coupled floating‐electrode dielectrophoresis (DEP), which yielded 80% of the sensor devices featuring between one and five CNTs, is developed. The mechanism of floating‐electrode DEP on full arrays and individual devices to understand its self‐limiting behavior is studied. The resistance distributions across the array of CNT devices with respect to different DEP parameters are characterized. The CNT devices are then operated as liquid‐gated CNT field‐effect‐transistors (LG‐CNTFET) in liquid environment. Current dependency to the gate voltage of up to two orders of magnitude is recorded. Finally, the sensors are validated by studying the pH dependency of the LG‐CNTFET conductance and it is demonstrated that 73% of the CNT sensors of a given microsystem show a resistance decrease upon increasing the pH value.