Dry electrode for the measurement of biopotential signals

This paper introduces a kind of silicon-based dry electrode for measuring biological signals.It uses microneedle arrays to penetrate into the stratum corneum to reduce skin impedance.The dry electrode requires neither skin preparation nor the electrolytic gel,is easy to use and causes no skin allergy.Two different technologies are chosen to manufacture microneedle arrays of dry electrode.One is deep dry etching combined with isotropic wet etching.The other is mechanical dicing combined with chemical wet etching (including isotropic wet etching and anisotropic wet etching).Microneedle arrays are coated with metal and divided into 25 mm 2 as dry electrode patch.Impedance testing shows that the impedance value of dry electrode can be comparable with that of commercial electrode in the 20 Hz-10 kHz frequency range.The steady-state visual evoked potential recording and analysis prove that the dry electrode can be used to detect electroencephalography.     

硅微机械陀螺的接口检测技术

研究了微陀螺的电容变化率为１０－７～１０－８时的微弱输出信号的检测技术,这是微机械器件研制中具有普遍性的技术难点。在研究检测微小电容变化量的积分电路的基础上,进一步采用了可抑制低频噪声和漂移的相关双采样技术,以及抑制由开关的电荷注入引起的误差的技术。     

Micromachined catheter flow sensor and its applications in breathing measurements in animal experiments

A combination of silicone oil and a parylene film coating was newly introduced in the packaging process of a catheter flow sensor for measuring breathing characteristics under high humidity conditions. The produced catheter flow sensor was used in two animal experiments described in this paper to verify its usefulness. At first, it was inserted into the air passage of a mouse, and then methacholine was given to it to provoke contraction of the air passage. The sensor could directly detect the breathing characteristics successfully. Then, the sensor was inserted into a rabbit bronchus by using a guide tube and a fiberscope. The position of the tube’s fore-end was confirmed from images taken using the fiberscope. The sensor directly evaluated the breathing characteristics of rabbits with and without a pneumothorax. We conclude from these results that our developed catheter flow sensor can be used in the future to directly measure the breathing characteristics in a bronchus.     

Micromachined gas sensors for environmental pollutants

An Au doped tin oxide thin film was deposited as base material for carbon monoxide detection over a micromachined substrate. The performances of a recent technique to heat the device, named fast pulsed temperature supply, are presented. This technique exploits the property that, due to the very low thermal mass of the membrane, the term required to reach steady state conditions is very short (about 40 ms). The sensor heater is periodically supplied for very short terms, hundred of milliseconds, and kept off for long ones, seconds or more. Besides a strong reduction of power consumption compared with isothermal characterization, an increase of sensitivity is observed. Different shapes of the heating wave were examined and results are summarized and compared. Received: 1 June 1999 / Accepted: 2 June 1999     

Micromachined infrared pneumatic detector for gas sensor

We present a micromachined IR detector based on the principle of a pneumatic cell and suited as an IR detector in a miniaturised gas sensor. The detector basically consists of a sealed cavity, in which the heat generated by absorbed IR light results in an increased gas pressure. This pressure rise is detected capacitively. The theoretical performance of a 1 mm² micromachined device is calculated, and it is shown that a detectivity of 3.6·10⁹ cm. Hz^1/2/W can be expected. Moreover, a pneumatic gas leak is proposed to avoid thermal drift. Using conventional Silicon micromachining techniques, a prototype was fabricated which confirmed the principle of operation., The experimental results are compared to the theory.     

Micromachined thermal shear-stress sensor for underwater applications

This paper reports the development of micromachined thermal shear-stress sensors for underwater applications. The thermal shear-stress sensor is a polysilicon resistor sitting atop a vacuum-insulated nitride diaphragm. Special challenges for underwater measurements, such as the waterproof coating and minimization of pressure crosstalk, have been addressed. More rigid diaphragms than the aerial sensors are implemented to increase the operating range and reduce pressure crosstalk, with the cost of larger power consumption and lower sensitivity. Sensors with different diaphragm dimensions and resistor lengths have been fabricated and tested. Nearly zero pressure sensitivity has been achieved by either reducing the diaphragm width or adjusting the sensing element length. The effects of overheat ratio and operating mode on the sensor's pressure crosstalk have been discussed. Parylene C is chosen as the waterproof material for the underwater shear-stress sensors. The primary failure mode is identified as the corrosion of the soldering pads.     

A Micromachined Quartz Resonator Array for Biosensing Applications

An 8-pixel micromachined quartz crystal resonator array with a fundamental resonance frequency of 66 MHz has been designed, fabricated, and tested. A compact impedance-spectrum-analyzer electronic interface has been developed and combined with the quartz resonator array to form the biosensing system. The sensor array was calibrated using water–glycerol solutions, and the performance was found to be exactly as expected. Measurement of the crosstalk between the sensor pixels showed an isolation of $sim$ 30 dB. Selective functionalization of the pixels was achieved through the use of aqueous 3, 3 $^{prime}$-Dithiobis (sulfosuccinimidylpropionate) (DTSSP) molecules. The adsorption of avidin on DTSSP gave a frequency signal of 60 kHz in comparison to unfunctionalized pixels. The specific adsorption of avidin on functionalized pixels was confirmed through fluorescence microscopy. Comparing the performance of the micromachined quartz crystal microbalance (QCM) with a commercial 5-MHz device, we found that the micromachined QCM has a 4.25 times higher signal-to-noise ratio. Based on the measurement of the noise and using three times the frequency noise as the limit for the detection of avidin molecules, we expect to resolve a minimum of $sim$1/960 of a monolayer of avidin corresponding to an aerial mass density resolution of 0.7 $hbox{ng/cm}^{2}$ .$hfill$[2008-0196]      

Micromachined low-loss microwave switches

The design and fabrication of a micromechanical capacitive membrane microwave switching device is described. The switching element consists of a thin metallic membrane, which has two states, actuated or unactuated, depending on the applied bias. A microwave signal is switched on and off when the membrane is switched between the two states. These switches have a switching on speed of less than 6 μs and a switching off speed of less than 4 μs. The switching voltage is about 50 V. The switches have a bowtie shape and showed low insertion loss of 0.14 dB at 20 GHz and 0.25 dB at 35 GHz, and isolation of 24 dB at 20 GHz and 35 dB at 35 GHz. These devices offer the potential for building a new generation of low-loss high-linearity microwave circuits for a variety of phased antenna arrays for radar and communications applications     

A Micromachined Dual-Backplate Capacitive Microphone for Aeroacoustic Measurements

This paper presents the development of a micro-machined dual-backplate capacitive microphone for aeroacoustic measurements. The device theory, fabrication, and characterization are discussed. The microphone is fabricated using the five-layer planarized-polysilicon SUMMiT V process at Sandia National Laboratories. The microphone consists of a 0.46-mm-diameter 2.25-mum-thick circular diaphragm and two circular backplates. The diaphragm is separated from each backplate by a 2-mum air gap. Experimental characterization of the microphone shows a sensitivity of 390 muV/Pa. The dynamic range of the microphone interfaced with a charge amplifier extends from the noise floor of 41 dB/ radicHz up to 164 dB and the resonant frequency is 178 kHz.     

Bulk Micromachined Titanium Microneedles

Microneedle-based drug delivery has shown considerable promise for enabling painless transdermal and hypodermal delivery of conventional and novel therapies. However, this promise has yet to be fully realized due in large part to the limitations imposed by the micromechanical properties of the material systems being used. In this paper, we demonstrate titanium-based microneedle devices developed to address these limitations. Microneedle arrays with in-plane orientation are fabricated using recently developed high-aspect-ratio titanium bulk micromachining and multilayer lamination techniques. These devices include embedded microfluidic networks for the active delivery and/or extraction of fluids. Data from quantitative and qualitative characterization of the fluidic and mechanical performance of the devices are presented and shown to be in good agreement with finite-element simulations. The results demonstrate the potential of titanium micromachining for the fabrication of robust, reliable, and low-cost microneedle devices for drug delivery     

Micromachined acoustic-wave liquid ejector

This paper describes the design and performance of micromachined, self-focusing acoustic-wave liquid ejector (AWLE) that requires no heat, nozzle, nor acoustic lens. The AWLE has a very simple device structure and is easy to fabricate. Three versions of AWLE have been designed, fabricated, and tested for an ink-jet printing application. Also developed are computer simulation and design aids that take into account the acoustic loss in water and the two-time wave reflections at the water-air and water-transducer interfaces. The AWLE has been observed to eject water droplets of about 5 μm in diameter with radio frequency (RF) pulses of 5 μs pulsewidth. Overall, the AWLE has been shown to be capable of improving the printing resolution and speed of ink-jet printing significantly     

谐振式微传感器低功耗专用信号源研究

为满足皆振式微传感器对信号源低功耗、低失真的要求,本文提出了一种对现有DDS(直接数字合成)技术进行改进的方案,将现有的零阶保持逼近改进成为折线逼近来减小失真,并通过详细的公式推导给出了改进后波形失真度THD(总谐波失真)的计算公式.最后给出了MATLAB仿真结果和电路实现结果来验证方案可行性.结果表明在同等失真度下本...     

硅微机械振动陀螺零偏温度补偿研究

在对某型硅微机械振动陀螺进行大量高低温环境试验的基础上,根据试验数据,建立了一种零偏温度补偿模型,并用该模型对新测的试验数据进行了预测补偿.补偿结果表明:硅微机械陀螺经该模型补偿后零偏可以减少一个数量级,补偿效果明显.     

Perchlorate selective membrane electrodes based on synthesized platinum(II) complexes for low-level concentration measurements

Three synthesized platinum(II) complexes, [PtR₂(NN)] (R = Me, p-MeC₆H₄ and p-MeOC₆H₄; NN = 2,2′-bipyridyl), were studied to characterize their ability as an anion carrier in a PVC membrane electrode. The polymeric membrane electrodes (PME) and also coated glassy carbon electrodes (CGCE) prepared with [Pt(p-MeOC₆H₄)₂(NN)] showed excellent response characteristics to perchlorate ions. The electrodes exhibited Nernstian responses to ClO₄⁻ ions over a wide concentration range from 5 × 10⁻⁷ to 4.0 × 10⁻¹ M for PME and 1.5 × 10⁻⁷ to 2.7 × 10⁻¹ M for CGCE with low detection limits (4.0 × 10⁻⁷ M for PME and 1.0 × 10⁻⁷ M for CGCE). The electrodes possess fast response time, satisfactory reproducibility, appropriate lifetime and, most importantly, good selectivity toward ClO₄⁻ relative to a variety of other common anions. The potentiometric response of the electrodes is independent of the pH of the test solution in the pH range 2.5–9.5. The proposed sensors were used in potentiometric determination of perchlorate ions in mineral water, urine samples and also samples containing interfering anions. The interaction of the ionophore with perchlorate ions was shown by UV–vis spectroscopy.     

Micromachined multichannel systems for the measurement of cellular metabolism

Using living cells as the biological recognition element in a biosensor has two important advantages: cell receptors provide functional rather than structural specificity, and the cells provide second messenger pathways that amplify the receptor/ligand binding events. Cellular responses can be detected by measuring extracellular acidification with a silicon sensor. By using silicon micromachining technology, we can integrate the fluidic pathways and chambers for immobilizing cells with the silicon sensor. We describe a multichannel chip in which each channel is etched into the surface, and has its own flow of tissue-culture medium past the cells. Measurements have been made on adherent cells in which a muscarinic acetylcholine receptor is transfected. Responses to the agonist carbachol are shown.     

Micromachined jets for liquid impingement cooling of VLSI chips

Two-phase microjet impingement cooling is a potential solution for removing heat from high-power VLSI chips. Arrays of microjets promise to achieve more uniform chip temperatures and very high heat transfer coefficients. This paper presents the design and fabrication of single-jets and multijet arrays with circular orifice diameters ranging from 40 to 76 /spl mu/m, as well as integrated heater and temperature sensor test devices. The performance of the microjet heat sinks is studied using the integrated heater device as well as an industry standard 1 cm/sup 2/ thermal test chip. For single-phase, the silicon temperature distribution data are consistent with a model accounting for silicon conduction and fluid advection using convection coefficients in the range from 0.072 to 4.4 W/cm/sup 2/K. For two-phase, the experimental results show a heat removal of up to 90 W on a 1 cm/sup 2/ heated area using a four-jet array with 76 /spl mu/m diameter orifices at a flowrate of 8 ml/min with a temperature rise of 100/spl deg/C. The data indicate convection coefficients are not significantly different from coefficients for pool boiling, which motivates future work on optimizing flowrates and flow regimes. These microjet heat sinks are intended for eventual integration into a closed-loop electroosmotically pumped cooling system.     

A Micromachined Refreshable Braille Cell

A new concept for the realization of a refreshable Braille cell is presented. An electrothermally controlled microactuator that exploits the hydraulic pressure due to the volumetric expansion of melted paraffin wax is described. The paraffin wax is contained within a bulk micromachined silicon container. The container is sealed using an elastic diaphragm of silicone rubber. The container is heated using gold microheaters located on an underlying glass substrate. All the layers used to make up the containers are bonded together using an overglaze paste. The complete 3$,times,$2 dot Braille cell has air gaps between containers, to prevent unwanted actuation by means of heat leakage from adjacent containers. The prototype Braille cell measures 7$,times,$8.5$,times,$2 mm$^3$and its raised dots are held in equilibrium by pulsed actuation voltages. To maintain a dot height at 50% of its maximum, a duty factor of more than 0.8 was found, with an average power of 0.30 W ($ PRF = 0.027$Hz). The total actuation time for a dot on an up/down cycle was$sim50$s. The dot height increases with an increasing duty factor with a fixed PRF, and increases with decreasing PRF with a fixed duty factor. A stable maximum dot height was achieved by reducing the cooling time.hfillhbox[1381]     

微机械薄膜热膨胀系数的测试结构

在微电子机械系统(MEMS)领域,薄膜的热膨胀系数对于微电子器件、MEMS器件,尤其是微热执行器的设计是一个十分重要的参数.本文详细介绍和分析了薄膜热膨胀系数的几种测试结构,对于微机械薄膜热膨胀系数在线测试结构的设计有一定的参考价值.