A three-axis SOI accelerometer sensing with both in-plane and vertical comb electrodes

A three-axis capacitive accelerometer based on silicon-on-insulator is designed and fabricated. In the accelerometer, totally eight groups of capacitors are compactly arranged around an octagonal proof mass. The four groups of capacitors along orthogonal direction with in-plane comb electrodes detect XY acceleration, while the other four groups of capacitors along diagonal direction with vertical comb electrodes detect Z acceleration. Measurements of in-plane and vertical motion by the respective in-plane and vertical comb electrodes enable direct detection for all the three axes with differential capacitive sensing scheme. For the fabricated accelerometer in the size of 4 × 4 mm², the capacitance sensitivities of in-plane and out-of-plane accelerometers are 145.3 and 9.1 fF/g, respectively.     

Design, fabrication and testing of a high performance silicon piezoresistive Z-axis accelerometer with proof mass-edge-aligned-flexures

This paper presents design, fabrication and testing of a quad beam silicon piezoresistive Z-axis accelerometer with very low cross-axis sensitivity. The accelerometer device proposed in the present work consists of a thick proof mass supported by four thin beams (also called as flexures) that are connected to an outer supporting rim. Cross-axis sensitivity in piezoresistive accelerometers is an important issue particularly for high performance applications. In the present study, low cross-axis sensitivity is achieved by improving the device stability by placing the four flexures in line with the proof mass edges. Various modules of a finite element method based software called CoventorWare^™ was used for design optimization. Based on the simulation results, a flexure thickness of 30 μm and a diffused resistor doping concentration of 5 × 10¹⁸ atoms/cm³ were fixed to achieve a high prime-axis sensitivity of 122 μV/Vg, low cross-axis sensitivity of 27 ppm and a relatively higher bandwidth of 2.89 kHz. The designed accelerometer was realized by a complementary metal oxide semiconductor compatible bulk micromachining process using a dual doped tetra methyl ammonium hydroxide etching solution. The fabricated accelerometer devices were tested up to 13 g static acceleration using a rate table. Test results of fabricated devices with 30 μm flexure thickness show an average prime axis sensitivity of 111 μV/Vg with very low cross-axis sensitivities of 0.652 and 0.688 μV/Vg along X-axis and Y-axis, respectively.     

An effective PDMS microfluidic chip for chemiluminescence detection of cobalt (II) in water

A microfluidic chip for the chemiluminescence detection of cobalt (II) in water samples, based on the measurement of light emitted from the cobalt (II) catalysed oxidation of luminol by hydrogen peroxide in basic aqueous solution, is presented. The microfluidic chip was designed and fabricated from polydimethylsiloxane using micro-molding method. Optimized reagents conditions were found to be 5.0 × 10^?4 mol/L luminol, 1.0 × 10^?2 mol/L hydrogen peroxide, and 8.0 × 10^?2 mol/L sodium hydroxide. The system can perform fully automated detection with a reagent consumption of only 2.4 μL each time. The linear range of the cobalt (II) ions concentration was 1.0 × 10^?10–1.0 × 10^?3 mol/L and the detection limit was 5.6 × 10^?11 mol/L with the S/N ratio of 3. The relative standard deviation was 4.6 % for 1.0 × 10^?5 mol/L cobalt (II) ions (n = 10).     

A MEMS sandwich differential capacitive silicon-on-insulator accelerometer

A differential capacitive accelerometer with simple process is designed, simulated, and fabricated. To achieve a precision structure dimension with fewer processing steps, the silicon device layer transfer technology is being used to built a sandwich accelerometer based on a silicon-on-insulator (SOI) wafer, which was assembled by glass-si-glass multilayer anodic bonding. Deep reactive ion etching is being used to define symmetric beams and large mass block of equal thickness together in SOI device layer (up to 100 μm) in a single step to avoid alignment error in double side process. An actual accelerometer which is designed for 50 g measure range is fabricated with six lithography steps. Measurement results show 0.1166 V/g sensitivity and 0.022 % nonlinearity error in ±1 g gravity static response test. The accelerometer also provides a power spectrum less than 10.49 μVrms/Hz^1/2 (89.97 μg/Hz^1/2) in a non-isolated laboratory environment with a capacitive interface circuit.     

MEMS-based microthruster with integrated platinum thin film resistance temperature detector (RTD), heater meander and thermal insulation for operation up to 1,000°C

We have fabricated microthruster chip pairs—one chip with microthruster structures such as injection capillaries, combustion chamber and converging/diverging nozzle machined using the deep reactive ion etching process, the other chip with sputtered platinum (Pt) thin film devices such as resistance temperature detectors (RTDs) and a heater. To our knowledge, this is the first microelectromechanical systems-based microthruster with fully integrated temperature sensors. The effects of anneal up to 1,050°C on the surface morphology of Pt thin films with varied geometry as well as with/without PECVD-SiO₂ coating were investigated in air and N₂ and results will also be presented. It was observed that by reducing the lateral scale of thin films the morphology change can be suppressed and their adhesion on the substrate can be enhanced. Chemical analysis with X-ray photoelectron spectroscopy showed that no diffusion took place between neighboring layers during annealing up to 1?h at 1,050°C in air. Electrical characterization of sensors was carried out between room temperature and 1,000°C with a ramp of ±5?Kmin^?1 in air and N₂. In N₂, the temperature-resistance characteristics of sensors had stabilized to a large extent after the first heating. After stabilization the sensors underwent up to eight further temperature cycles. The maximum drift of the sensor signal was observed for temperatures above 950°C and was less than 8.5?K in N₂. To reduce the loss of combustion heat, chip material around microthruster structures was partially removed with laser ablation. The effects of thermal insulation were investigated with microthruster chip pairs which were clamped together mechanically. The heater was operated with up to 20?W and the temperature distribution in the chip pairs with/without thermal insulation was monitored with seven integrated RTDs. The experiments showed that a thermal insulation allows the maximum temperature as well as the temperature gradient within the microthruster chip pairs to be increased.     

A novel architecture design for VLSI implementation of integer DCT in HEVC standard

This paper presents novel hardware of a unified architecture to compute the 4?×?4, 8?×?8, 16?×?16 and 32?×?32 efficient two dimensional (2-D) integer DCT using one block 1-D DCT for the HEVC standard with less complexity and material design. As HEVC large transforms suffer from the huge number of computations especially multiplications, this paper presents a proposition of a modified algorithm reducing the computational complexity. The goal is to ensure the maximum circuit reuse during the computation while keeping the same quality of encoded videos. The hardware architecture is described in VHDL language and synthesized on Altera FPGA. The hardware architecture throughput reaches a processing rate up to 52 million of pixels per second at 90 MHz frequency clock. An IP core is presented using the embedded video system on a programmable chip (SoPC) for implementation and validation of the proposed design. Finally, the proposed architecture has significant advantages in terms of hardware cost and improved performance compared to related work existing in the literature. This architecture can be used in ultra-high definition real-time TV coding (UHD) applications.

     

一种电容式微机械加速度计的设计

介绍了一种新型基于滑膜阻尼的电容式微机械加速度计.该加速度计根据差分电容极板间正对面积的改变来检测加速度大小,保证了输出电压与加速度之间的线性度.对加速度计进行了结构设计和分析.给出了加速度计的制作工艺流程,研究了解决深反应离子刻蚀过程中的过刻蚀现象的方法.初步测试结果表明,该加速度计的灵敏度比较理想,谐振频率与理论计算相吻合.     

Dark energy or local acceleration?

We find that an observer with a suitable acceleration relative to the frame comoving with the cosmic fluid, in the context of the FRW decelerating universe, measures the same cosmological redshift as in the ΛCDM model. The estimated value of this acceleration is β ? 1.4 × 10^?9 m/s². We discuss two different scenarios, a motion with constant acceleration and a helical motion (although other alternatives are also likely), and we show that the final value of the peculiar velocity is sensitive to the type of the peculiar motion.     

The fulfillment of a three step-size models pedometer based on accelerometer and embedded system

Pedometers are known to have steps estimation issues. This is mainly attributed to their innate acceleration-based measuring sensory. This work proposes a novel implementation of microcontroller and accelerometer sensor, based for three step-size models pedometer in calorie consumption calculation. To verify the output voltage stability of accelerometer sensor, the methods of statistics analysis are introduced to extract the useful features. Three kinds of different steps are employed to obtain the analytic data. The proposed pedometer dimension of a proto-type is 68?mm (L)?×?42?mm (W)?×?15?mm (H).     

Microcapillary electrophoresis chip with a bypass channel for autonomous compensation of hydrostatic pressure flow

The application of chip-based microcapillary electrophoresis (µCE) to determine the electrophoretic mobility of molecules and particles has been intensively studied in the last two decades. Balancing the hydrostatic pressure between both ends of the microchannel is essential for free-zone electrophoresis and highly accurate measurement. This balancing operation appears simple on a macroscale (e.g., >?10^?3 m); however, on a microscale (e.g., 10^?6–10^?3 m), it is not straightforward because of the complexity of the interface dynamics at the meniscus. The hydrostatic pressure flow is unstable because of the small size of the microchannel, which is smaller than a single droplet of water. In this study, a µCE chip design was proposed by adding an extra bypass channel to balance the fluid level of the two open reservoirs and inhibit the generation of hydrostatic pressure flow within the microchannel. The fluid behaviors in the microchannel and current and voltage (I–V) characterization were experimentally studied. In addition, a numerical simulation of the electroosmotic flow and hydrostatic flow in the µCE chip was performed. The comparison between the µCE chip with and without the bypass channel showed that the bypass channel did not produce a disturbance in the microchannel for the electrophoretic measurement. The simple microchannel design enabled autonomous compensation of the hydrostatic pressure from the instability of the meniscus, and thus improved the usability of the chip-based µCE chip and the accuracy in the electrophoretic measurement.     

Design and simulation of a high-performance Z-axis SOI-MEMS accelerometer

This paper presents a new micromachined z-axis accelerometer as well as a new method to sense the out-of-plane displacement capacitively via comb finger arrays. The new design built the z-accelerometer using eight folded beam suspension to minimize the off axis sensitivities in both the x- and y- directions. The proposed method implements the sensing electrode as a comb finger arrays surrounding the sensor. This method enables the realization of the sensor by bulk micromachining process, increases the sense capacitance and reduces the off-axis sensitivity. This process allows building the micromachined accelerometer with large inertial mass. This work introduces the design and simulation for this accelerometer. The introduced method results in a high sense capacitance as well as high sensitivity. The simulated sense capacitance is 19.6627 pF. The sensor sensitivity is 2.037 μm/g with a very small total noise equivalent acceleration of 3.096 μg/ $ \sqrt {Hz} $ .     

Chemiluminescence detection for Cu (II) based on 1,10-Phenanthroline-hydrogen peroxide reaction on a PDMS microfluidic chip

A simple, rapid and effective method for the determination of copper (II) in water on a PDMS microfluidic chip with chemiluminescence (CL) detection is presented. The CL reaction was based on oxidation of 1,10-phenanthroline by hydrogen peroxide in basic aqueous solution. Polydimethylsiloxane (PDMS) was chosen as material for fabricating the microfluidic chip with two steps lithography method. Optimized reagents conditions were found to be 6.0 × 10^?5 mol/L 1,10-phenanthroline, 1.2 × 10^?3 mol/L hydrogen peroxide, 6.5 × 10^?2 mol/L sodium hydroxide and 2.0 × 10^?3 mol/L Hexadecyl trimethyl ammonium Bromide (CTMAB). In the continuous flow injection mode the system can perform fully automated detection with a reagent consumption of only 3.4 μL each time. The linear range of the Cu (II) ions concentration was 1.0 × 10^?8 mol/L to 1.0 × 10^?4 mol/L, and the detection limit was 9.2 × 10^?9 mol/L with the S/N ratio of 3. The relative standard deviation was 2.8 % for 1.0 × 10^?6 mol/L Cu (II) ions (n = 8). The most notable features of the detection method are simple operation, rapid detection and easy fabrication of the microfluidic chip.     

一种新结构硅微机械压阻加速度计

设计、制造并测试了一种新结构硅微机械压阻加速度计.器件结构是悬臂梁-质量块结构的一种变形.比较硬的主悬臂梁提供了一定的机械强度,并且提供了高谐振频率.微梁很细,检测时微梁沿轴向直拉直压.力敏电阻就扩散在微梁上,质量块很小的挠动就能在微梁上产生很大的应力,输出很大的信号.5 V条件下,灵敏度为14.80 mV/g,谐振频率为994 Hz,分别是传统结构压阻加速度计的2.487倍和2.485倍.加速度计用普通的N型硅片制造,为了刻蚀高深宽比的结构,使用了深反应离子刻蚀(DRIE)工艺.     

Microelectromechanical systems vibration powered electromagnetic generator for wireless sensor applications

This paper presents a silicon microgenerator, fabricated using standard silicon micromachining techniques, which converts external ambient vibrations into electrical energy. Power is generated by an electromagnetic transduction mechanism with static magnets positioned on either side of a moving coil, which is located on a silicon structure designed to resonate laterally in the plane of the chip. The volume of this device is approximately 100 mm³. ANSYS finite element analysis (FEA) has been used to determine the optimum geometry for the microgenerator. Electromagnetic FEA simulations using Ansoft’s Maxwell 3D software have been performed to determine the voltage generated from a single beam generator design. The predicted voltage levels of 0.7–4.15 V can be generated for a two-pole arrangement by tuning the damping factor to achieve maximum displacement for a given input excitation. Experimental results from the microgenerator demonstrate a maximum power output of 104 nW for 0.4g (g=9.81 m s^?1) input acceleration at 1.615 kHz. Other frequencies can be achieved by employing different geometries or materials.     

Zenith scattered light measurement: observations of BrO and OClO

Stratospheric BrO and OClO observations have been made for the first time over a tropical station, Pune (18° 31′ N, 73° 55′ E) using a Differential Optical Absorption Spectroscopy (DOAS) technique by measuring zenith sky scattered light spectra in the wavelength range of 346–358 nm by ultraviolet (UV)/visible spectrometer. The Differential Optical Density (DOD) fitting technique is applied for the right selection of a suitable spectral region for the analysis to minimize interference and poorly fitting absorption features, and also to minimize the residual of the fit. Observed DODs of O₃, NO_2, BrO, OClO, O₄, Rayleigh and Ring are well fitted with the calculated DODs and the percentage DODs are found to vary up to 0.5%, 0.8%, 0.15%, 0.13%, 1.5%, 1.2% and 1.3% respectively. Chlorine and bromine species play an important role in the ozone depletion, hence O₃, NO₂, BrO and OClO Slant Column Densities (SCDs) are derived between 76° and 94° Solar Zenith Angles (SZAs). The SCDs of O₃ are found to be decreased in the twilight period (i.e. between 90° and 94° SZA) in the presence of sufficient BrO and OClO. Total Column Densities (TCDs) of O₃, NO₂, BrO and OClO are derived by UV/visible spectrometry, Brewer spectrometry and satellite-based Scanning Imaging Absorption spectrometer for Atmospheric Cartography (SCIAMACHY) for Pune and the higher latitude station Kanpur (26° 28′ N, 80° 24′ E) during the period 1 April–31 June 2008. The day-to-day variations in O₃ and NO₂ TCDs over Pune are found to be more than over Kanpur. BrO TCDs vary between 1.9?×?10¹³ and 4?×?10¹³ molecules cm^?2 over Pune, which are derived by UV/visible spectrometry, while they vary for the high-altitude station Kanpur between 0.5?×?10¹³ and 3.5?×?10¹³ molecules cm^?2 derived by SCIAMACHY. The OClO TCDs are found to have an increasing trend with variations between 2?×?10¹³ and 4.5?×?10¹³ molecules cm^?2 during the above period.     

光电加速度传感器非对称3×3解调系统SOPC设计

介绍了集成光学芯片、光纤质量块简谐振子和可编程片上系统(SOPC)混合集成光学加速度计的设计方法.采用基于3×3耦合器的干涉系统进行光相位的调制.研究了在非对称情况下的解调算法,从而解决了由于非对称性造成解调结果失真的问题.应用SOPC技术设计和实现数字信号处理系统,实现信号处理与数据传输的并行工作,实验证明该系统可以实时、线性地跟踪到加速度信号.实际测量灵敏度为4.62 V/gn,工作频带为1-1 066 Hz.     

The genuine short GRB 090227B and the disguised by excess GRB 090510

GRB 090227B and GRB 090510, traditionally classified as short gamma-ray Bursts (GRBs), indeed originate from different systems. For GRB 090227B we inferred a total energy of the e ⁺ e ^? plasma \(E_{e^ + e^ - }^{tot} \) = (2.83 ± 0.15) × 10⁵³ erg, a baryon load of B = (4.1 ± 0.05) × 10^?5, and a CircumBurstMedium (CBM) average density 〈n _CBM〉 = (1.90 ± 0.20) × 10^?5 cm^?3. From these results we have assumed the progenitor of this burst to be a symmetric neutron stars (NSs) merger with masses m = 1.34 M_⊙, radii R = 12.24 km. GRB 090510, instead, has \(E_{e^ + e^ - }^{tot} \) = (1.10 ± 0.06) × 10⁵³ erg, B = (1.45 ± 0.28) × 10^?3, implying a Lorentz factor at transparency of Γ = (6.7 ± 1.7) × 10², which are characteristic of the long GRB class, and a very high CBM density, 〈n _CBM〉 = (1.85 ± 0.14) × 10³ cm^?3. The joint effect of the high values of Γ and of 〈n _CBM〉 compresses in time and “inflates” in intensity in an extended afterglow, making appear GRB 090510 as a short burst, which we here define as “disguised short GRB by excess” occurring an overdense region with 10³ cm^?3.     

Quantitative analysis of microfluidic mixing using microscale schlieren technique

In this study, we discuss the employment of microscale schlieren technique to facilitate measurement of inhomogeneities in a micromixer. By mixing dilute aqueous ethanol and water in a T-microchannel, calibration procedures are carried out to obtain the relation between the concentration gradients and grayscale readouts under various incident illuminations, concentrations of aqueous ethanol solution, and knife-edge cutoffs. We find that to broaden measuring range with minimal error, the luminous exitance should be tuned to have a reference background with an average grayscale readout of 121, and dilute aqueous ethanol solution with a mass fraction of 0.05 should be used along a 50 % cutoff. For concentration gradients greater than 6.8 × 10^?3 or below ?2.5 × 10^?2 μm^?1, the calibration curves show great linearity. Correspondingly, the discernable limit of our microscale schlieren system is 2.3 × 10^?5 μm^?1 for a positive refractive index gradient and ?8.6 × 10^?5 μm^?1 for a negative refractive index gradient. Once the relation between concentration gradients and grayscale readouts is known, the concentration distribution in a microfluidic can be reconstructed by integrating its microscale schlieren image with appropriate boundary conditions. The results prove that the microscale schlieren technique is able to provide spatially resolved, noninvasive, full-field measurements. Since the microscale schlieren technique is directly linked to the measurement of a refractive index gradient, the present method can be easily extended to other scalar quantifications that are related to the variation of refractive index.     

Sea ice small-scale surface roughness estimation based on AMSR-E observations

In this article, the retrieval of a sea ice small-scale surface roughness parameter using a proposed model is investigated at several Advanced Microwave Scanning Radiometer Earth Observing System (AMSR-E) channels (6.9, 10.7, and 89 GHz) over the Arctic oceans. The AMSR-E 89 GHz observations with a spatial resolution of approximately 6 km?× 4 km, nearly three times the resolution of the currently operational radiometer SSM/I 85 GHz (15 km?× 13 km), are fully exploited to retrieve the total and multiyear (MY) ice concentrations through the utilization of the ARTIST sea ice (ASI) and polarization corrected temperature (PCT) algorithms, respectively. To improve the accuracy of the retrieved ice concentration, a tie-point adaption scheme was used to obtain daily adaptable tie-points for the two ice concentration algorithms. A sea ice small-scale roughness parameter was then calculated with the model proposed by Hong for the above-mentioned three frequencies. At lower frequencies, such as 6.9 and 10.7 GHz, roughness estimates are available for all ice types. However, estimates at 89 GHz are physically illegitimate over the wintertime MY ice cover. The model estimates at the two low frequencies were further studied over a protracted period (2003–2010). The annual time series of the averaged estimate over the Arctic sea ice were found to exhibit a slightly decreasing trend (?2.1 × 10^?3 and??1.9 × 10^?3 cm year^?1 for 6.9 and 10.7 GHz, respectively). Meanwhile, the winter time series showed an increasing trend whereas the summer time series showed a remarkably decreasing trend, which indicates more serious melting activity occurring over the Arctic ice.     

Production of uniform droplets using membrane, microchannel and microfluidic emulsification devices

This review provides an overview of major microengineering emulsification techniques for production of monodispersed droplets. The main emphasis has been put on membrane emulsification using Shirasu Porous Glass and microsieve membrane, microchannel emulsification using grooved-type and straight-through microchannel plates, microfluidic junctions and flow focusing microfluidic devices. Microfabrication methods for production of planar and 3D poly(dimethylsiloxane) devices, glass capillary microfluidic devices and single-crystal silicon microchannel array devices have been described including soft lithography, glass capillary pulling and microforging, hot embossing, anisotropic wet etching and deep reactive ion etching. In addition, fabrication methods for SPG and microseive membranes have been outlined, such as spinodal decomposition, reactive ion etching and ultraviolet LIGA (Lithography, Electroplating, and Moulding) process. The most widespread application of micromachined emulsification devices is in the synthesis of monodispersed particles and vesicles, such as polymeric particles, microgels, solid lipid particles, Janus particles, and functional vesicles (liposomes, polymersomes and colloidosomes). Glass capillary microfluidic devices are very suitable for production of core/shell drops of controllable shell thickness and multiple emulsions containing a controlled number of inner droplets and/or inner droplets of two or more distinct phases. Microchannel emulsification is a very promising technique for production of monodispersed droplets with droplet throughputs of up to 100?l?h^?1.