Use of a surface-acoustic-wave sensor to characterize the reaction of styrene vapor with a square-planar organoplatinum complex

A coated surface-acoustic-wave (SAW) sensor is used to probe the reaction of styrene vapor with the square-planar platinum-ethylene pi-complex, trans-PtCl2(ethylene)(pyridine). A dual-SAW delay-line oscillator configuration is employed: one oscillator is coated with a solvent-cast film of the solid platinum-ethylene complex dispersed in a poly(isobutylene) matrix, and the second oscillator is coated only with polymer. Absorbed styrene vapor displaces ethylene to form the stable styrene-substituted complex, trans-PtCl2(styrene)(pyridine), causing a decrease in the oscillator frequency from the increase of mass on the surface of the sensor. For short-term exposures, there is a linear relationship between the logarithm of the rate of frequency change and the logarithm of the styrene vapor concentration, consistent with a power-law kinetic model for the heterogeneous trapping reaction. Deviation from this relationship above 300 ppm at 25 degrees C is attributed to the onset of multilayer adsorption of styrene at the surface of the trapping reagent. The sensor response exhibits an Arrhenius temperature dependence permitting estimation of the thermal activation energy for the olefin-substitution reaction. Calculated detection limits of 3 and 0.6 ppm of styrene vapor are achieved for operation at 25 and 40 degrees C, respectively.     

Trace detection of hydrogen peroxide vapor using a carbon-nanotube-based chemical sensor

The sensitive detection of hydrogen peroxide in the vapor phase is achieved using a nanochemical sensor consisting of single-walled carbon nanotubes as the sensing material. The interdigitated electrode-based sensor is constructed using a simple and standard microfabrication approach. The test results indicate a sensing capability of 25 ppm and response and recovery times in seconds. The sensor array consisting of 32 sensor elements with variations in sensing materials is capable of discriminating hydrogen peroxide from water and methanol.     

Application of a surface-acoustic-wave device for measurement of liquid flow rate

The use of a surface-acoustic-wave (SAW) device to measure the flow rate of liquids is described. A delay-line stabilized SAW oscillator heated to a suitable temperature above ambient is cooled by the flowing fluid. This results in a change in the oscillator frequency. The frequency of a 68-MHz oscillator operated at 9 degrees C above ambient is found to vary by more than 40 kHz for variation in water flow rate from 0 to 0.8 ml/min. Attractive features of this device include the ability to measure very low flow rates (less than 0.1 mul/min) and direct digital output. However, since this is a thermal type of flow sensor, the temperature of the fluid will be slightly elevated during its passage through the flow cell. The device should be useful in applications where low flow rates have to be monitored.     

Analysis of measurement errors of convective heat-transfer coefficient using a thin-walled heat-flux sensor

A theoretical ana lysis of the errors is made and it is shown that the convective heat–transfer coefficient in steady conditions on a rotating object of investigation can be measured by thin-walled sensors.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol.35, No. 2, pp. 243–249, August, 1978.     

Removal of styrene vapor from waste gases by a trickle-bed air biofilter

The trickle-bed air biofilter (TBAB) performance for the removal of high-strength styrene was evaluated under different gas flow rates and influent concentrations. Under pseudo-steady-state conditions, the elimination capacity increased but the removal efficiency decreased with the increase of styrene loading. More than 90 and 80% removal efficiencies were achieved for influent styrene loadings below 32 and 55g/m(3)/h, respectively. The TBAB appears to be an effective treatment process for controlling high-strength styrene emission under low-to-medium loading conditions, and the effectiveness could be maintained over 140 days of laboratory operation.     

Deposition of diamond coating on pure titanium using micro-wave plasma assisted chemical vapor deposition

The nucleation and growth of diamond coatings on pure Ti substrate were investigated using microwave plasma assisted chemical vapor deposition (MW-PACVD) method. The effects of hydrogen plasma, plasma power, gas pressure and gas ratio of CH₄ and H₂ on the microstructure and mechanical properties of the deposited diamond coatings were evaluated. Results indicated that the nucleation and growth of diamond crystals on Ti substrate could be separated into different stages: (1) surface etching by hydrogen plasma and the formation of hydride; (2) competition between the formation of carbide, diffusion of carbon atoms and diamond nucleation; (3) growth of diamond crystals and coatings on TiC layer. During the deposition of diamond coatings, hydrogen diffused into Ti substrate forming titanium hydride and led to a profound microstructure change and a severe loss in impact strength. Results also showed that pre-etching of titanium substrate with hydrogen plasma for a short time significantly increased the nuclei density of diamond crystals. Plasma power had a significant effect on the surface morphology and the mechanical properties of the deposited diamond coatings. The effects of gas pressure and gas ratio of CH₄ and H₂ on the nucleation, growth and properties of diamond coatings were also studied. A higher ratio of CH₄ during deposition increased the nuclei density of diamond crystals but resulted in a poor and cauliflower coating morphology. A lower ratio of CH₄ in the gas mixture produced a high quality diamond crystals, however, the nuclei density and the growth rate decreased dramatically.     

Conformal aluminum oxide coating of high aspect ratio structures using metalorganic chemical vapor deposition

The metalorganic chemical vapor deposition of aluminum oxide has been studied over a wide process parameter range. Electrical properties of as-grown and annealed layers have been investigated using planar aluminum/aluminum oxide/silicon capacitors. The best processing conditions resulted in a leakage current of 10 nA/cm² at an equivalent oxide thickness of 3.6 nm. In addition, the film conformality was evaluated on silicon trench structures with aspect ratios of up to 60. Excellent step coverage of over 90% (thickness at trench bottom to thickness at trench middle) was achieved at temperatures below 400 °C and a pressure of 100 Pa. After annealing the electrical properties of these layers, analyzed on planar test structures, were comparable to the results obtained at higher deposition temperature.     

Detection of noncharged organic substances by new measurement method using a lipid membrane sensor

This paper reports a new measurement method to detect ppb levels of noncharged organic substances using lipid/polymer membrane sensors. Noncharged organic substances have large influences on the adsorption of positively-charged lipids to negatively-charged membranes. Organic solvents (trichloroethylene) and endocrine disrupting chemicals (di-2-ethylhexylphthalate) were detected by utilizing the sensor output, which is the change of membrane potential caused by interactions among the lipid membrane, noncharged organic substances, and lipids in solution. This new potentiometric method has a possibility of detection of a trace amount of noncharged toxic substances.     

Contact-independent measurement of electrical conductance of a thin film with a nanoscale sensor

Contact effects are a common impediment to electrical measurements throughout the fields of nanoelectronics, organic electronics, and the emerging field of graphene electronics. We demonstrate a novel method of measuring electrical conductance in a thin film of amorphous germanium that is insensitive to contact effects. The measurement is based on the capacitive coupling of a nanoscale metal-oxide-semiconductor field-effect transistor (MOSFET) to the thin film so that the MOSFET senses charge diffusion in the film. We tune the contact resistance between the film and contact electrodes and show that our measurement is unaffected. With the MOSFET, we measure the temperature and field dependence of the conductance of the amorphous germanium, which are fit to a model of variable-range hopping. The device structure enables both a contact-independent and a conventional, contact-dependent measurement, which makes it possible to discern the effect of the contacts in the latter measurement. This measurement method can be used for reliable electrical characterization of new materials and to determine the effect of contacts on conventional electron transport measurements, thus guiding the choice of optimal contact materials.     

双通道传递函数法测量矢量水听器自噪声

针对矢量水听器自噪声测量时受环境干扰严重的问题,提出了利用双通道传递函数法测量矢量水听器的自噪声。给出了双通道传递函数法降低环境干扰的原理;并通过实验手段分析了利用该方法测量时,环境背景噪声条件及水听器布放距离等因素对测量结果的影响。研究结果表明,利用双通道传递函数法测量矢量水听器的自噪声,可以有效降低环境背景噪声影响,得到更加准确的结果。该方法为准确测量矢量水听器的自噪声提供了有效的手段,为矢量水听器在远程探测领域的实际工程应用提供了测量基础。     

大时间常数传感器动态特性的在线实时补偿

在测控系统中传感器通常都位于系统的反馈通道.大时间常数的传感器严重地影响着系统的实时调节,为此,对大时间常数的传感器进行在线的实时补偿是十分必要的.本文通过分析,给出了对大时间常数传感器动态特性进行在线实时补偿的算法,该算法根据传感器在当前以及此前若干时刻的测量输出值yk,yk-1,yk-2直接给出现场被测量实际值的估计值xk,从而摆脱了由于大时间常数传感器的惯性给系统的实时调节带来的困难.为了实现对传感器的动态特性进行补偿,文章还给出了对传感器模型进行在线辨识的方法.     

表面等离子共振双光束差分研究和数值模拟

为提高光强调制型表面等离子共振传感器的灵敏度和抗干扰能力,本文提出了一种采用双光束差分光强的SPR检测新方法.通过对该方法的理论计算和数值模拟分析,得到了不同入射角和不同金膜厚度时,反射光强差与样品折射率之间的关系曲线.研究表明,与传统的光强调制方法相比,当两束光入射角相差5°,金膜厚度在40～50 nm时,该方法是有更高的灵敏度和更宽的测量范围,并且由于采用了光强差分技术,大大提高了传感器的抗干扰性和稳定性.     

Wavefront error measurement of high-numerical-aperture optics with a Shack-Hartmann sensor and a point source

We developed a new, to the best of our knowledge, test method to measure the wavefront error of the high-NA optics that is used to read the information on the high-capacity optical data storage devices. The main components are a pinhole point source and a Shack-Hartmann sensor. A pinhole generates the high-NA reference spherical wave, and a Shack-Hartmann sensor constructs the wavefront error of the target optics. Due to simplicity of the setup, it is easy to use several different wavelengths without significant changes of the optical elements in the test setup. To reduce the systematic errors in the system, a simple calibration method was developed. In this manner, we could measure the wavefront error of the NA 0.9 objective with the repeatability of 0.003 lambda rms (lambda = 632.8 nm) and the accuracy of 0.01 lambda rms.     

Selective binding and detection of magnetic labels using PHR sensor via photoresist micro-wells

We have developed a novel platform for selective binding of magnetic labels on planar Hall resistance sensor (PHR) for biosensing applications. The photoresist (PR) micro wells were prepared on the PHR sensor junctions to trap the magnetic bead at specified locations on the sensor surface and thin layer of Au was sputtered in the PR wells immobilize bimolecular. The Au surface is functionalized with single-stranded oligonucleotide and further biotin was used to immobilize streptavidin coated magnetic labels (Dynabeads Myone 1.0 microm, Invitrogen Co.). After removal of the PR wells on the sensor surface the non specific binding magnetic labels were successfully removed and only the chemically bounded magnetic labels were remained on the Au surface for detection of biomolecules using PHR sensor. We controlled the number of magnetic labels on the PHR sensor surface by using different sizes of the PR well on the junctions. The specifically bounded magnetic labels were successfully detected by characterizing the individual PHR sensor junctions. This technique enables the complete control over the magnetic labels for selective binding of biomolecules on the sensor surface for increasing the sensitivity of the PHR sensor as well as removal of the non specific bindings on the sensor surface.     

Finite element analysis of an optical fibre electric field sensor using piezoelectric polymer coating

Abstract

A novel approach for analysing an optical fibre electric field sensor by using the finite element method is presented. A singlemode optical fibre carrying a transversely poled piezoelectric poly(vinylidene fluoride) polymer coating was successfully modelled by using three-dimensional analysis. The response of the optical fibre electric field sensor was determined over a wide frequency range from 100 Hz to 50MHz. The modelling predicts a phase shift of 0.019 rad V^?1 m^?1 in the low frequency (axially unconstrained) region and 0.000 82 rad V^?1 m^?1 in the high frequency (axially constrained) region. At frequencies higher than 7 MHz the optical response is dominated by radial resonances of the fibre—jacket composite. Good agreement exists between the resonance peaks predicted by the simulation and those theoretically calculated using composite theory.     

Initiated chemical vapor deposition of a siloxane coating for insulation of neural probes

Recent advances in the field of neuroprosthetics have brought the possibility of human utilization into the near term. However, current implant coating chemistries require thicknesses of ~ 25 μm in order to provide the required electrical insulation, significantly increasing the diameter of the neural probe shanks and resulting surgical damage upon implantation. In this work, a novel biopassivation coating is created through initiated chemical vapor deposition (iCVD) of trivinyl-trimethyl-cyclotrisiloxane. The resulting material is a highly crosslinked organosilicon polymer matrix which is synthesized directly on the surface of the substrate. This material possesses an electrical resistivity which allows for a coating thickness on the order of only 5 μm. The material has also been demonstrated to retain its electrical properties in a simulated biological environment for over 3 years.     

Optical temperature sensor and thermal expansion measurement using a femtosecond micromachined grating in 6H-SiC

An optical temperature sensor was created using a femtosecond micromachined diffraction grating inside transparent bulk 6H-SiC, and to the best of our knowledge, this is a novel technique of measuring temperature. Other methods of measuring temperature using fiber Bragg gratings have been devised by other groups such as Zhang and Kahrizi [in MEMS, NANO, and Smart Systems (IEEE, 2005)]. This temperature sensor was, to the best of our knowledge, also used for a novel method of measuring the linear and nonlinear coefficients of the thermal expansion of transparent and nontransparent materials by means of the grating first-order diffracted beam. Furthermore the coefficient of thermal expansion of 6H-SiC was measured using this new technique. A He-Ne laser beam was used with the SiC grating to produce a first-order diffracted beam where the change in deflection height was measured as a function of temperature. The grating was micromachined with a 20 microm spacing and has dimensions of approximately 500 microm x 500 microm (l x w) and is roughly 0.5 microm deep into the 6H-SiC bulk. A minimum temperature of 26.7 degrees C and a maximum temperature of 399 degrees C were measured, which gives a DeltaT of 372.3 degrees C. The sensitivity of the technique is DeltaT=5 degrees C. A maximum deflection angle of 1.81 degrees was measured in the first-order diffracted beam. The trend of the deflection with increasing temperature is a nonlinear polynomial of the second-order. This optical SiC thermal sensor has many high-temperature electronic applications such as aircraft turbine and gas tank monitoring for commercial and military applications.     

High-performance fiber strain sensor of carbon nanotube/thermoplastic polyurethane@styrene butadiene styrene with a double percolated structure

In this work, a high-performance fiber strain sensor is fabricated by constructing a double percolated structure, consisting of carbon nanotube (CNT)/thermoplastic polyurethane (TPU) continuous phase and styrene butadiene styrene (SBS) phase, incompatible with TPU (CNT/TPU@SBS). Compared with other similar fiber strain sensor systems without double percolated structure, the CNT/TPU@SBS sensor achieves a lower percolation threshold (0.38 wt.%) and higher electrical conductivity. The conductivity of 1%-CNT/TPU@SBS (4.12×10⁻³ S·m⁻¹) is two orders of magnitude higher than that of 1%-CNT/TPU (3.17×10⁻⁵ S·m⁻¹) at the same CNT loading of 1 wt.%. Due to double percolated structure, the 1%-CNT/TPU@SBS sensor exhibits a wide strain detection range (0.2%–100%) and an ultra-high sensitivity (maximum gauge factor (GF) is 32411 at 100% strain). Besides, the 1%-CNT/TPU@SBS sensor shows a high linearity (R² = 0.97) at 0%–20% strain, relatively fast response time (214 ms), and stability (500 loading/unloading cycles). The designed sensor can efficiently monitor physiological signals and movements and identify load distribution after being woven into a sensor array, showing broad application prospects in wearable electronics.     

Digital signal processing for biaxial position measurement with a pyroelectric sensor array

This paper proposes a new full digital approach to estimate biaxial position with a pyroelectric sensor array. The previously developed analog interface shows its limits in the calibration procedure, requiring several trimming adjustments. A DSP-based hardware has been developed to experimentally evaluate three digital methods: radial basis function (RBF) neural network, best fitted plane (BFP), and look-up table (LUT) in the least mean square (LMS) error sense. Experimental results show that no dramatic improvements are obtained by the RBF, despite the long training required and the external PC support for weight calculation. The BFP reaches performances comparable to the analog processing system using only nine calibration points, but the best tradeoff has been found with the LUT technique. Actually, with a 64-point calibration set, LUT gives a root mean square error (RMSE) of 0.5% with respect to full scale (FS), offering a valid in-circuit compensation of array structural defects.