Search

Capacitive micromachined ultrasonic transducers (CMUTs) have been widely utilized in applications of biomolecule monitoring, ultrasound medical diagnosis, and ultrasound therapy because of their advantages in high-level integration with integrated circuits, good impedance matching for acoustic transmission, and flexible element and array configuration compared with conventional piezoelectric ceramic transducers. Crosstalk effects on dynamics of a CMUT element, i.e. electrical, mechanical, and acoustic performance, would lead to unexpected spurious resonances. In this study, the mutual interaction from fluid and nearby cells in a CMUT element is newly investigated specially aiming to characterize their coupling effects with series and parallel parasitic effects based on a nonlinear Equivalent Circuit Model (ECM). The mutual interaction is evaluated with the electromechanical and acoustic characteristics by comparison between ECM and 3D Finite Element Analysis (FEA). Two representative CMUT element configurations, that are the rectangular with nine cells and the hexagonal with seven cells, are analyzed with different center-to-center distance. The radii of cells are set to be lambda 8 with different edge-to-edge distances. The parasitic effects are modeled by a series parasitic factor and a parallel-capacitance parasitic ratio. The coupling influence of crosstalk and parasitic effects on the performance of a CMUT element is evaluated, such as the impedance, phase, conductance, velocity, and ultrasound pressure field. The results of ECM-FEA-based methods show good agreements, and the improved ECM can be used for co-parasitic extraction with front-end interface.

Reduced graphene oxide (rGO) fiber as a carbon-based fiber sensor has aroused widespread interest in the field of gas sensing. However, the low response value and poor flexibility of the rGO fiber sensor severely limit its application in the field of flexible wearable electronics. In this paper, a flexible and wearable nylon fiber sensor modified by rGO and ZnO quantum dots (QDs) is proposed for wide-range NO2 gas detection at room temperature. The response value of the nylon fiber sensor to 100 ppm NO2 gas is as high as 0.4958, and the response time and recovery time are 216.2 s and 667.9 s, respectively. The relationship between the sensor’s response value and the NO2 concentration value is linear in the range of 20–100 ppm, and the fitting coefficient is 0.998. In addition, the test results show that the sensor also has good repeatability, flexibility, and selectivity. Moreover, an early warning module was also designed and is proposed in this paper to realize the over-limit monitoring of NO2 gas, and the flexible sensor was embedded in a mask, demonstrating its great application potential and value in the field of wearable electronics.

Tactile sensors have been widely used in the areas of health monitoring and intelligent human-machine interface. Flexible tactile sensors based on nanofiber mats made by electrospinning can meet the requirements of comfortability and breathability for wearing the body very well. Here, we developed a flexible and self-powered tactile sensor that was sandwich assembled by electrospun organic electrodes and a piezoelectric layer. The metal-free organic electrodes of thermal plastic polyurethane (PU) nanofibers decorated with multi-walled carbon nanotubes were fabricated by electrospinning followed by ultrasonication treatment. The electrospun polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) mat was utilized as the piezoelectric layer, and it was found that the piezoelectric performance of PVDF-TrFE nanofiber mat added with barium titanate (BaTiO3) nanoparticles was enhanced about 187% than that of the pure PVDF-TrFE nanofiber mat. For practical application, the as-prepared piezoelectric tactile sensor exhibited an approximative linear relationship between the external force and the electrical output. Then the array of fabricated sensors was attached to the fingertips of a glove to grab a cup of water for tactile sensing, and the mass of water can be directly estimated according to the outputs of the sensor array. Attributed to the integrated merits of good flexibility, enhanced piezoelectric performance, light weight, and efficient gas permeability, the developed tactile sensor could be widely used as wearable devices for robot execution end or prosthesis for tactile feedback.

This study investigates the sensing characteristics of micromachined electromagnetic cantilevers vibrating at different resonance orders and under static or flowing liquid immersions. The cantilever is designed with a wide-plate structure, which contributes to the modal optimization for basic and higher-order torsions. The fluid-structure interaction is used to analyze the parameterized expressions of the density and its changing sensitivity based on the cantilever’s flexural and torsional vibrations. They have successfully clarified the comprehensive factors that influence the density measurement performance. The study shows that the analytical predictions for the density changing sensitivity agree well with the experimental results. The experiments prove that the cantilever under flowing immersion appears significantly degraded in its density measurement accuracy. Higher mode and shorter length enable the cantilever to respond better density sensing behaviors under flowing immersion. These results here can be further generalized to guide the optimal design of cantilever-based resonators in flowing liquid monitoring.

The electronic spin polarization of alkali-metal-vapor atoms is a pivotal parameter for atomic magnetometers. Herein, a novel method is presented for determining the spin polarization with a miniaturized single-beam spin-exchange-relaxation-free (SERF) magnetometer on the basis of zero-field cross-over resonance. Two separate laser beams are utilized to heat the cell and interrogate the vapor atoms, respectively. Spin polarization can be extracted by measuring the resonance response signal of the magnetometer to the transverse magnetic field under different irradiances. Results of these experiments are consistent well with the theoretical predictions with the maximum deviation less than 4%. The proposed method has the integrated advantages of possessing a simple configuration and in-situ measurement. Furthermore, combined with a homemade optical differential detection system with a factor of approximately three of the power noise suppression, the developed single-beam SERF atomic magnetometer with a measuring sensitivity of 32 fT/Hz1/2 has been achieved. This demonstrated approach can help guide the development of chip-scale atomic magnetometers for bio-magnetic field imaging applications.

This paper presents the new design and fabricating process of a packaged micro piezoelectric vibration energy harvester (PVEH). Structures are designed and parameters are optimized through finite element modelling and analysis. The double L-shaped tungsten proof mass block and thick copper-based PZT bimorph are proposed to ensure the harvester with high electrical power. Polymethyl methacrylate (PMMA) packaging and epoxy resin bonding supply the flexible clamping of piezoelectric cantilever, which decreases the resonant frequency, increase average PZT stress, reduces the maximum PZT stress and broadens the effective frequency range. Bulk PZT bonding is used in PVEH prototype fabrication. Experimental results show that the packaged PVEH resonates under the excitation of 1 g (9.8 m s−2) at 160 Hz. It has an optimum resistance load of 47 kΩ. More importantly, its maximum output power is 2.49 mW in experiments, and the half-power bandwidth is 22 Hz. After package, it has a high volume power density of 0.64 mW/cm3 g2 with the volume of 3.9 cm3 (2 cm × 1.5 cm × 1.3 cm). Connected with energy harvesting circuit, PVEH can light up a light emitting diode (LED) under broadband vibration frequency. The proposed PVEH with broadband output power in mW level is promised to power up some microelectronic devices for application.

In this paper, based on the basic characteristics of microwave, a new method of generating microwave landing signal is presented in the form of fourth power creatively using Gaussian beam generation method, which is commonly used in microwave generation method. The Gaussian microwave landing signal generated by the new algorithm in this paper can make the pulse scan in the baseband phase of the signal to meet the requirements of the international civil aviation convention. Compared with the conventional Gaussian microwave beam generation method previously adopted, the new algorithm proposed in this paper is simpler and more effective in the actual application and operation process, and can greatly save development resources, which provides a better scheme reference for the generation of microwave landing signal in engineering practice.

A novel probe-type thin film thermocouple has been fabricated successfully for high temperature measurement applications. WRe26 (tungsten-26% rhenium)-In

In order to deal with the problem that electronic device can be affected by electromagnetic interference from external environment, this paper studied the influence of the proposed rectangular metallic enclosures to achieve effective electromagnetic shielding based on finite-integration technique. A three-dimensional simulation model of a rectangular shielding enclosure was directly established with the plane wave of timebased Gaussian pulse excitation, which was utilized to establish electromagnetic radiation intensity. The electromagnetic shielding effectiveness was simulated both in frequency domains and in time domains, with different apertures numbers on front of rectangular enclosure. The thickness parameter was further investigated, which is essential to increase the operating stability of electronic system. It needed to have high capability in anti-electromagnetic interference to ensure the efficient transmission of weak signals.

This paper presents a micromachined piezoelectric resonator based on microcantilever with out-of-plane vibration for liquid density and viscosity determination. The microcantilever mainly contained a T-beam and four piezoresistive beams, which has significantly different vibration modes in liquid compared with fundamental plate microcantilever. The focus was set on 2nd out-of-plane vibrational mode, excited in a novel wave-shaped operation mode in liquid media. Finite element simulations were performed to optimize the operation mode and analyze the resonance characteristics. A high quality factor of 223 was achieved in cyclohexane at 71 kHz, and the sensitivity was calculated by four organic liquids, and 34 Hz/$\left(\mathbf{k g} \cdot \mathbf{m}^{-3}\right)$ was achieved. The results indicated that the proposed novel resonator with wave-shaped mode reached high quality factor as well as high sensitivity in liquids measurements.

In this paper, a novel resonant pressure sensor is developed based on electrostatic excitation and piezoresistive detection. The measured pressure applied to the diaphragm will cause the resonant frequency shift of the resonator. The working mode stress–frequency theory of a double-ended tuning fork with an enhanced coupling beam is proposed, which is compatible with the simulation and experiment. A unique piezoresistive detection method based on small axially deformed beams with a resonant status is proposed, and other adjacent mode outputs are easily shielded. According to the structure design, high-vacuum wafer-level packaging with different doping in the anodic bonding interface is fabricated to ensure the high quality of the resonator. The pressure sensor chip is fabricated by dry/wet etching, high-temperature silicon bonding, ion implantation, and wafer-level anodic bonding. The results show that the fabricated sensor has a measuring sensitivity of ~19 Hz/kPa and a nonlinearity of 0.02% full scale in the pressure range of 0–200 kPa at a full temperature range of −40 to 80 °C. The sensor also shows a good quality factor >25,000, which demonstrates the good vacuum performance. Thus, the feasibility of the design is a commendable solution for high-accuracy pressure measurements. The operating principle and experimental realization of a new piezoresistive resonant pressure sensor are shown. Resonant pressure sensors rely on changes in applied pressure to a diaphragm to cause the resonant frequency of the resonator to change. This enables high stability and signal-to-noise ratios, combined with a quasi-digital output; resultantly, resonant pressure sensors are often used in critical applications such as aerospace and for instrument calibration. Here, a team led by Zhuangde Jiang from Xi’an Jiaotong University, China, report a piezoresistive detection-based resonant pressure sensor. They establish the theory for their device operation, verified by both simulations and experiments. Their device shows an accuracy better than 0.02% FS and a resonant quality factor greater than 25,000.

The performance of microcantilever-based resonator working under different operation modes is analyzed in fluid density determination at different flow velocities. A setup is designed to control the liquid flow velocity along normal and tangential directions in the range of 0-4.37 m/s. Microcantilever-based resonators are fabricated with different lengths, which are excited to vibrate under 1st bending and 2nd torsion modes. The experimental results show that the normal flow velocity plays a leading role to impair the density measuring accuracy. The microcantilever-based resonator with shorter length and in higher order vibration mode is demonstrated to have a better measurement performance in flowing liquids.

Generally, CMUTs are composed of numbers of independent cells, whose edges are clamped on the posts. Such structure is characterized with high resonant frequency and high sensitivity. However, too much parasitic capacitance is often induced for the CMUTs because of the posts between cells, causing a low electromechanical coupling coefficient. At the same time, the collapse voltage is too high and does not have low power consumption characteristics. A through-hole CMUTs (TH-CMUTs) structure is proposed, which is clamped at the four corners of membrane. It has many advantages on the premise of ensuring the ultrasonic emission power and output current. Since the stiffness of TH-CMUTs structure is reduced, its collapse voltage can be greatly reduced. The original membrane on the post is suspended, then the original parasitic capacitance is transformed into the effective capacitance to increase the electromechanical coupling coefficient. Finally, the structure also has the characteristics of high filling ratio. All the advantages of proposed TH-CMUTs structure are simulated and validated.

A novel micro-electromechanical resonator based on in-plane mode was presented for the measurements of fluid density and viscosity. With the purpose of enhancing the quality factor of micro resonator, double vibrators were connected by a center beam to not only drive the resonant structure in in-plane vibration mode but also reduce the vibration stress to be concentrated in the fixed terminal. Finite element analysis and numerical simulation were conducted to analyze and optimize the resonator structure. Based on the simulated analysis, its quality factor reached highly to 96 in ethanol with the resonant frequency of approximately 34 kHz. And the stress amplitude up to MPa on the center beam had strong relationship with both of the fluid characteristics and output voltage, which benefited to improve the measurement accuracy of fluid density and viscosity based on the piezoresistive principle.

Electrostatically actuated microplates with multilayer and material anisotropy properties, are widely employed in microelectromechanical systems. However, previous theories rarely consider the aforementioned properties simultaneously, hindering their widespread application. This paper proposes a general theoretical model for electrostatically actuated rectangular multilayer anisotropic microplates subjected to residual stress and hydrostatic pressure by combining the classical laminated thin plate theory, Galerkin method and a partial expansion approach for nonlinear electrostatic force. This model enables successful establishment of closed-form expressions for the main mechanical behaviors, e.g. the pull-in voltage, static deflection, and resonant frequency. Validation of these expressions, using finite element method simulations and experimental results, shows significant improvement in the analysis accuracy (15 times higher) compared to those theories neglecting the material anisotropy, as well as excellent applicability across a wide range of DC voltages and dimensions. Additionally, the influences of electrostatic softening effects and scale effects on the theories are also discussed.

Broadband low-frequency vibration and shock energies are ubiquitous such as biomechanical motion, which can be harvested to power wearable electronics. This paper proposes a compact design of V-shaped piezoelectric vibration energy harvester (V-PVEH) with impact stopper. To demonstrate V-PVEH having high power density, Euler beam model is proposed for qualitative comparison between V-PVEH and cantilevered piezoelectric vibration energy harvester (C-PVEH). FEA model in COMSOL for V-PVEH structure design is proposed especially for the stress check. Modal analysis, two bimorphs connection style, tip mass thickness, and acceleration amplitude are discussed in the experimental vibration validation. A peak voltage of 11.5 V at a low resonant frequency of 12 Hz and a maximum power of 0.442 mW are shown in experiments under the excitation of 0.1 g. A lumped parameters model with nonlinearity analysis for impact induced broadband and shock input is discussed comprehensively. The stopper design in V-PVEH can not only limit the vibration amplitude and prevent overload, but also form broadband of 8−15 Hz and generate large voltage output of 5−19 V when impact occurs at an acceleration of 0.4 g. Except for resonating excitation, biomechanical shock energy harvesting with ultra-low frequency of 1 Hz is testified for wearable V-PVEH to charge a 10 μF capacitor to 10 V in 5 s by stamping feet. Above all, V-PVEH with stopper is believed to show good performance in broadband low-frequency vibration and biomechanical shock energy harvesting.

A novel probe-type thin film thermocouple has been fabricated successfully for high temperature measurement applications. WRe26 (tungsten–26% rhenium)–In2O3 thermoelectric materials were used in the thermocouples to achieve high thermoelectric output and high temperature resistance. The films were deposited on a cylindrical substrate by magnetron sputtering technology. The annealing process of the thermocouples was studied to achieve optimal performance. The calibration results showed the thermoelectric output of WRe26–In2O3 thin film thermocouples reached 93.7 mv at 700 °C, and its sensitivity was 165.5 µV/°C under the temperature of the cold junction, which was 133.8 °C. The thermocouples developed in this work have great potential for practical applications.

In order to improve the measuring accuracy of micro-electromechanical system (MEMS) resonant sensor with micro-cantilever structure to measure fluid density, a temperature compensation method is presented. The elastic modulus of the micro-cantilever is calculated considering its temperature coefficient so that the working equation to measure fluid density is obtained with decreasing temperature disturbance on the measuring accuracy. The simulations and experimental measurements of several fluids with different densities were carried out by the MEMS micro-cantilever resonant sensor under different temperatures. The simulation analyses showed that the fluid densities measured by using the proposed resonant density sensor with temperature compensation were more fitted with the reference density values than those without temperature compensation. The experimental results showed that both the measuring accuracy and stability of the MEMS micro-cantilever resonant sensor in fluid density measurement were increased more than twice based on the temperature compensation method. Therefore, the proposed temperature compensation method is important to improve the measuring precision and stability of the MEMS micro-cantilever resonant sensor in fluid density detection fields.

This paper presents a novel PMUTs excitation method based on parametric excitation. An extra AC perturbation voltage at twice the frequency of the main excitation frequency was superimposed on the conventional sinusoidal excitation voltage. Finite element analysis and numerical simulation was conducted for an air-coupled bimorph PMUTs. The level of amplification was related to the phase difference between the perturbation & driving voltage and the quality factor of the structure. Compared with the conventional bimorph PMUTs, the transmission sensitivity of the PMUTs excited by parametric excitation method, can be improved by more than 200% around 1 MHz working frequency. In the end a verification experiment was conducted to verify the amplification ability of the parametric excitation method.

This paper presented a novel piezoelectric micromachined ultrasonic transducer (PMUT) based on mechanical coupling between an annular diaphragm and a circular diaphragm stacking together. The circular diaphragm whose pedestal grounded on the middle of the annular diaphragm, which formed a base excitation system. Compared to non-coupled traditional circular diaphragm PMUTs, the proposed PMUTs achieved higher transmission sensitivity by 173% with the resonant frequency of 6.14 MHz in water, due to the base excitation amplification of the circular diaphragm. Also, the array transmission performance of the proposed PMUT and non-coupled traditional PMUT with circular diaphragm was compared in the same array dimension. The results indicated that the array composed by the proposed PMUT had less cross-talk effect, which kept the central working frequency almost the same when it work solely.

In this paper, we have designed and fabricated the capacitive micromachined ultrasonic transducers (CMUTs) by low temperature bonding process under 350 °C. And the electrospinning technology is innovatively applied as a coating method for the functionalization of CMUTs' top membrane to achieve a uniform fiber structure, which is beneficial to absorbing and releasing the biochemical gas, that is to say, it can be applied to recycling use. It was further demonstrated that the mass effect on functionalized CMUTs' resonant frequency has been distinctly intensified with the increase of direct current (DC) bias voltage V bias between the top and bottom electrodes from 10V to 30V, the resonant frequency changes from 1.787 MHz to 1.664 MHz. Simultaneously volume sensitivity was calculated from 200.000 ppb/Hz to 78.125 ppb/Hz with the concentration of sulfur dioxide (SO 2 ) from 100 ppm to 333 ppm. By applying appropriate V bias , not only the volume sensitivity can be flexibly guaranteed, but also the energy consumption will be reduced.

Electrospun-based ZnO granular nanofibers (GNFs), with the granular feature which are able to modulate energy band along axises of the fibers, are regarded as great candidates to develop the UV photodetectors with high performance. However, when exposed to air, the oxygen absorption and desorption make the devices suffer from sluggish response. Here, via an easy and cost effective method of polydimethylsiloxane (PDMS) coating, the photo-response speed of electrospun-based ZnO GNFs photodetectors was enhanced by more than 104 times. The giant enhancement was attributed to both gas isolation and surface electron state passivation. The results exhibited an effective method to enhance response speed of electrospun-based GNFs photodetectors.

A novel magnetic field sensor is developed based on the microcantilever resonator to realize the parameter measurements of in-plane multi-axis magnetic field under different vibration modes. The working equations of the resonant sensor are established to calculate the strength and direction angle of measured magnetic field based on different resonances. The strength components of magnetic field along x-axis and y -axis are independently measured by the proposed resonant sensor under flexural and torsional resonant modes, respectively. The corresponding outputs of the sensor are linearly related to the magnetic field strength components. The finite element simulations are performed not only to prove the capability of the sensor to measure magnetic field under different modes, but also indicate the mode coupling of microcantilever resonator existed in the measurement. Thus, the coupling compensation method is proposed by amending ouput voltage of the sensor through experiments. The experimental results at atmospheric pressure show that the compensated accuracies of in-plane magnetic field are 3.06% (strength) and 1.59% (angle), and the measuring sensitivities are 98.79 µV mT−1 along x-axis and 92.46 µV mT−1 along y -axis, respectively.

MEMS-based piezoelectric vibration energy harvesters (MEMS-PVEHs) with center mass block are designed with the overall size 10 × 10 × 2 mm3, two prototypes including piezoelectric unimorph and bimorph beams are used respectively. This paper studies the characteristics of MEMS-PVEHs by modeling and simulation in COMSOL. Their eigenfrequencies are analyzed firstly, their optimal piezoelectric outputs are explored by changing excitation frequency and load resistance secondly, then the piezoelectric unimorph and bimorph beams are compared finally. The simulation results show that the optimal excitation frequency is slightly higher than the eigenfrequency, and the maximum piezoelectric power of the PVEH can be obtained only when the appropriate excitation frequency and load resistance are selected, and the power generation efficiency is 0.5. It has little difference between unimorph and bimorph to improve the MEMS-PVEH piezoelectric output. Finally, the piezoelectric unimorph with double opposite electrodes is designed based on the MEMS fabrication process.

To explore the predictive value of high-sensitivity C reactive protein (hsCRP) in middle-aged population during the peripheral arteriosclerosis.Random sampling method was used in the study. In 2006-2007 Kailuan Group health examination of 101,510 employees, using stratified random sampling method to select 5,852 as observational cohort included, in the final with a standard queue 5,440 in December 2009. This study selected to participate in the 2012-2013 health examination cohort as the research object, in accordance with the inclusion criteria ultimately selected survey 3,978, select the epidemiological investigation, physical examination, laboratory testing data analysis. Of the 3 978 subjects, 2,282 were male and 1,696 were female, and the baseline age was (53.80±11.14) years. According to the baseline hsCRP quartile level was divided into four groups for comparison of baseline data, using multiple linear regression analysis between hsCRP and brachial-ankle pulse wave velocity (baPWV). Area under the receiver operating characteristic (ROC) curve (AUC) was used to evaluate the prediction of hsCRP levels in peripheral arteriosclerosis.With increase of hsCRP levels, the survey of baseline levels of baPWV showed increasing trend, (1,445.49±300.55), (1,494.46±307.94), (1,547.67±320.34), (1,621.32±342.53) cm/s, respectively. Multiple linear regression results showed that age, by logarithmic transformation of hsCRP (lghsCRP) level, systolic blood pressure and fasting blood glucose for each additional unit, baPWV levels were increased 266.47, 58.00, 5.02, 39.79 cm/s (P0.001), and BMI for each additional unit, baPWV level decreased 9.52 cm/s (P=0.030). The prediction of hsCRP in peripheral artery showed that lghsCRP level of AUC to 0.59 (95% CI: 0.57-0.61), lower than the age and systolic blood pressure predicted value AUC (95% CI) of 0.69 (0.67-0.71), 0.75 (0.73-0.77), respectively.The hsCRP level could not predict the peripheral arteriosclerosis alone, and the combined age and systolic blood pressure level could have better predictive value.

Novel three-dimensional (3D) continuously graded phononic crystals (CGPCs) have been designed, and fabricated by 3D printing. Each of the CGPCs is an entity instead of a combination of several other samples, and the porosity distribution of the CGPC along the incident direction is nearly linear. The sound absorption characteristics of CGPCs were experimentally investigated and compared with those of uniform phononic crystals (UPCs) and discretely stepped phononic crystals (DSPCs). Experimental results show that CGPCs demonstrate excellent sound absorption performance because of their continuously graded structures. CGPCs have higher sound absorption coefficients in the large frequency range and more sound absorption coefficient peaks in a specific frequency range than UPCs and DSPCs. In particular, the sound absorption coefficients of the CGPC with a porosity of 0.6 and thickness of 30 mm are higher than 0.56 when the frequency is 1350–6300 Hz and are all higher than 0.2 in the studied frequency range (1000–6300 Hz). CGPCs are expected to have potential application in noise control, especially in the broad frequency and low-frequency ranges.

In this article, the experimental studies on ignition mechanisms and combustion characteristics of the micro combustor have been made for the designs and ignition of the combustor. A set of special experimental devices of ignition are designed and fabricated based on Si-based MEMS technology. The combustors of the experimental devices are the square cavity that varied from 1mm to 9mm in length and from 0.5mm to 4mm in height. The spark electrodes are Au electrodes. The gaps of electrodes are 10μm, 40μm, and 100μm. The experiments of the ignition mechanisms of premixed H2/air, the concentration limit of ignition, residence time, ignitor-breakdown voltage, and heat transfer have been made on the devices. The ignition mechanisms and combustion characteristics of H2/air in micro combustor have been discussed based on the results of experiments. The experimental results indicate that the ignition of the premixed H2/air in micro combustor is feasible. The range of the ignitable concentration has a significant reduction. The combustion is subject to the back-fire and liable to suffer from flame extinction. The height is at least larger than 0.61mm. The ignitor-breakdown voltage is at least 350V when the gap of ignition electrodes is 10μm.

In this paper, a new type micro piston internal combustion engine is reported. The micro engine can be used to provide mechanical energy for micro electric power generation system. It is consisted of three or four planar plate structure. This micro engine has special advantages in structure which are more suitable to minimize whole engine to MEMS dimensions than traditional engines. Compared with traditional or other existing micro piston engines, there is a sliding chute and crank mechanism rather than a crank and connecting rod mechanism to improve the space utilization ratio. The crank is fixed on the plate next to the main body plate of the engine. A free piston micro engine without the crank and connecting rod mechanism is given too. Scheme of structure, operation and characters of the micro engine are described in detail. The displacement, velocity and acceleration functions of piston are deduced to understand the rules of piston motion. Calculating formulas of porting parameters are deduced too. Finally, an example of the micro engine with specific design parameters is given. Mathematic modeling of the porting parameters is built. The calculation results show that the phase angles of the inlet, scavenging port and the exhaust port of the example engine are respectively of 21.78°, 156.27° and 158.39° under following conditions. Compression ratio is 5; working volume is 5mm3; length of stroke is 2mm; the sectional dimension of the piston is 2mm×1mm; and the value of revolution is 9000RPM. When the width of gas ports are all 1mm, the heights of inlet, scavenging port and exhaust port corresponding to the port phase angles above are respectively 72μm, 85μm, and 70μm. According to the assembly testing on computer, it is shown that the micro piston engine presented here is workable, controllable and suitable for MEMS fabrication in structure. It can be used as device to provide mechanical energy for micro electric power generation system.

SF6 /O2 Plasma cryo-etching is discussed to show that it is a promising technology for etching the high aspect ratio silicon structures. Through a series of etching experiments, process factors including chuck temperature, gas composition, chamber pressure and ICP coil power are variated to show their influences to the etching results. Some valuable details of the experiment data point to some key mechanisms of the cryo-etching. It is not the surface chemical reaction but the ion bombardment that dominates the cyro-etching process in most cases. Notching near to the mask is due to the discharging effects of dielectric layer, and ARDE effect here is also different from the usual etching processes but is driven by the sidewall step coverage effect to the ion sputtering.Copyright © 2007 by ASME

Vorticity-stream function method is successfully used to solve an incompressible gas flow in the parallel-plates micro-channel. A new formula in finite difference scheme is developed to describe the boundary vorticity based on the slip boundary theory and Taylor series expansion. Results show that the boundary vorticity are not only influenced by the Knudsen number (Kn) but also influenced by the tangential momentum accommodation coefficient (TMAC).Copyright © 2007 by ASME

To enable MEMS designers to create fabrication-ready models of MEMS devices in an intuitive environment, this paper describes a MEMS design strategy that uses parameterized three-dimensional (3D) part features to construct geometric models of MEMS devices and then generates mask-layouts and process flows automatically. SolidWorks, an outstanding 3D design tool, is utilized to build the 3D model of the MEMS device. Most frequently-used 3D MEMS part features are created in SolidWorks and saved to a user database through Application Programming Interfaces (APIs) of SolidWorks. When designing a MEMS device, the designer develops its 3D model by selecting 3D part features from the database, and then uses Finite Element Analysis (FEA) to refine the model until it exhibits the desired characteristics. Next, the model is used to generate mask-layouts and process flows. Finally, it is necessary to verify whether the mask-layouts and process flows are generated correctly by reconstructing them into a 3D geometric model and comparing it to the designed 3D model. If there are differences between them, the designer is supposed to modify the mask-layouts and process flows until they can result in the desired shape of the MEMS device.