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Transmission electron microscopy (TEM) is a highly effective method for scientific research, providing comprehensive analysis and characterization. However, traditional TEM is limited to observing static material structures at room temperature within a high-vacuum environment. To address this limitation, a microchip was developed for in situ TEM characterization, enabling the real-time study of material structure evolution and chemical process mechanisms. This microchip, based on microelectromechanical System (MEMS) technology, is capable of introducing multi-physics stimulation and can be used in conjunction with TEM to investigate the dynamic changes of matter in gas and high-temperature environments. The microchip design ensures a high-temperature uniformity in the sample observation area, and a system of tests was established to verify its performance. Results show that the temperature uniformity of 10 real-time observation windows with a total area of up to 1130 μm2 exceeded 95%, and the spatial resolution reached the lattice level, even in a flowing atmosphere of 1 bar. [ABSTRACT FROM AUTHOR]

Flow measurement is an essential requirement in medical, industrial, automotive and environmental applications, Thanks to the rapid development of microelectromechanical system (MEMS) micro-fabrication techniques, silicon-based microflow sensor chips used as the key component of microfluidic control systems have attracted particular attentions due to the miniaturized chip-size, high precision, low power consumption, rapid response and low-cost batch-fabrication capability. Up to present, many different types of silicon microflow sensors have been proposed and developed. This paper provides a review on recently completed works on design, fabrication and properties of the MEMS-based silicon monolithic microflow sensors. Some technical challenges and application outlooks are also discussed in the paper. [ABSTRACT FROM AUTHOR]

This paper presents a dual quantization lateral-axis capacitive electromechanical sigma–delta modulator (EM- \Sigma \Delta \mathrm M ) vibratory wheel gyroscope under mode-matched condition. A symmetric wheel gyroscope structure was designed, fabricated, and wafer-level packaged under vacuum. The EM- \Sigma \Delta \mathrm M interface loop adopts a fourth-order multifeedback and local resonator \Sigma \Delta \mathrm M noise shaping structure, taking advantage of single-bit and multibit quantization in a single-loop modulator. To evaluate the influence of quantization noise, various numbers of bits of the multibit quantizator were compared and the optimal number of bits was calculated. The interface circuit system was implemented in hardware based on a low-noise front-end application-specified integrated circuit and a back-end discrete-time EM- \Sigma \Delta \mathrm M realized in a field-programmable gate array chip. The system clock was generated using a self-clocking scheme, which allows interfacing to gyroscope with a wide range of drive frequencies. Experimental evaluation indicated that the digital gyroscope system achieved a scale factor of 2073LSB(4.1 mV)/deg/s, with a nonlinearity of 0.046%, a noise floor of 3.1 m°/s/ $\surd $ Hz within a bandwidth of 100 Hz, and a bias instability of 1.3 deg/hr. [2017-0081] [ABSTRACT FROM PUBLISHER]

In the microelectromechanical systems (MEMS) field, low-range (e.g., kPa or sub-kPa) differential pressure sensors have remained difficult for decades. Generally, there are two unsolved problems that hinder volume production and wide applications in consumer-electronics. First, high sensitivity required very thin and large sensing diaphragm normally fabricated with low yield, and thus, high selling price. Second, high sensitivity required large deflection of the diaphragm easily causeing severe output of non-linearity that degrades the detecting precision. This paper reports a so-called thin-film under bulk (TUB) MEMS technique to high-yield fabricate high-performance low-range pressure sensors for smart central air-conditioning systems. With the single-wafer-based TUB structure, pressure-induced stress is highly concentrated in a bulk-silicon beam-island structure for piezoresistive readout, where a very thin but uniform poly-silicon diaphragm can be formed beneath the bulk-silicon structure to sustain the pressure. The beam-island reinforced structure brings about decreased deflection and highly linear output. Micro-columns are also formed under the bulk-silicon islands as over-range protection stoppers that are important for low-range pressure sensor. After the description about the 1.2 mm $\times 1.2$ mm tiny-sized sensor-chip design and its single-wafer fabrication process, a test is conducted that results in 22-mV output for 1.2-kPa measure range and very good linearity of ±0.05% (FS). About $100\times $ over-range protection capability of the sensor is also achieved. The novel high-yield TUB process can be used for low-cost production of high-performance pressure sensors for the applications of new-generation smart central air-conditional systems and spirometers, etc, and the bulk/surface combined TUB micromachining technique promises to be widely used for the formation of various complex MEMS structures. [2016-0309] [ABSTRACT FROM PUBLISHER]

A MEMS based vacuum packaging method is developed for uncooled optically readable infrared focal plane array (OR-IRFPA). The vacuum packaging structure is made up of three layers: a glass visible window, a silicon spacer, and a silicon infrared window. The silicon spacer is bonded with the glass visible window to form two cavities: one cavity for getter and another one for OR-IRFPA. The isolation wall with micrometer scale pores is designed to ensure air's free flow between two cavities and prevent getter powder from harming pixels of OR-IRFPA. The infrared window is used as cover board and selectively transmitting 8-14 μm infrared radiation. Infrared images of human body are gotten by using the vacuum packaged OR-IRFPA, which shows the vacuum packaging method is feasible and useful for OR-IRFPA. [ABSTRACT FROM AUTHOR]

This paper reports a self-aligned process for the fabrication of a high aspect ratio stepped polysilicon electrode with sub-micron capacitive gaps, which increases the coupling factor in capacitive driving and sensing. In contrast to the previous works, the polysilicon electrodes, which are formed by refilling the trenches and etching back, are anchored on the surfaces of steps in the trenches and etched by two-step deep reactive ion etching. The polysilicon electrodes are self-aligned and perfectly symmetric. Because of the 'U'-shaped profile produced by the refilling process, the polysilicon electrode is less sensitive to a stress gradient in Low-pressure chemical vapor deposition (LPCVD) polysilicon layer. A thin layer of heavily doped polysilicon and a low-stress polysilicon layer, instead of uniform, heavily doped polysilicon, are used to form the polysilicon electrodes without sacrificing the electrical performance, which decreases the deposition time for LPCVD significantly due to the much faster deposition of normal low-stress polysilicon. To validate the study, a single-crystal silicon length extensional mode resonator with a 300-nm capacitive gap is fabricated based on this process. The frequency of the resonator is measured to be 25.5955 MHz, with a quality factor of 67,656 under 20 Pa. [ABSTRACT FROM AUTHOR]

This paper presents a micromechanical resonant gas sensor, which is operated in extensional bulk mode, for high-accuracy sensing of ultra-low concentration chemical vapors. The designed and fabricated gravimetric resonant microsensor has exhibited both high Q-factor of 11157 in air and high mass sensitivity of 10.16 Hz pg−1. Much more importantly, both theoretical analysis and sensing experiment have verified that such an extensional resonance mode is technically advantageous in sensing accuracy (e.g., output signal linearity in terms of gas concentration and reproducibility of sensitivity), which can be attributed to the uniform vibration amplitude at each point of the gas-adsorbing area. Loaded with –COOH functionalized mesoporous-silica nanopaticles as sensing material, which features an ultra-large surface area, the chemical sensing micro-resonator experimentally performs precise detection performance to ppm-level ammonia vapor. The limit of detection is as low as 1 ppm and the response time of the sensor is as short as 10 s. [ABSTRACT FROM AUTHOR]

This paper reports a novel top-down/bottom-up combined resonant microcantilever chemical sensor, where the nanosensing material of a functionalized mesoporous thin film (MTF) is directly self-assembled on the sensing region of the integrated microcantilever. By using the batch-producible nano-on-micro construction technique, a large number of such sensors can be batch fabricated with uniform performance and low cost. More importantly, the sensing molecule terminals can be simultaneously constructed at the pore inner surface when the MTF is directly grown on the cantilever. With -\NH2-group-functionalized MTF directly grown onto the surface of the cantilever free end, the micro-/nanocombined gravimetric sensor has experimentally exhibited quick response and highly sensitive detection of \CO2 gas. [ABSTRACT FROM PUBLISHER]

This paper reports novel single-wafer-based piezoresistive micro flow sensors, which are bulk micromachined only from the front side of the silicon wafer to facilitate the sensor-bare chips directly packaged into micro-fluidic systems with low-cost surface mounting technology (SMT). With neither double-sided micromachining nor multiwafer bonding needed, two structural types of the piezoresistive flow sensors are designed and fabricated in (1 1 1) wafers, where 'type A' sensor has a smaller channel cross section area compared to 'type B' sensor. After the bare sensor chip directly attached on a printed circuit board (PCB), wire bonded between the pads and the PCB for electric interconnection and the inlet/outlet front side connected, deionized water is flowed into the both types of flow sensors to characterize piezoresistive output of the differential pressure sensing elements in terms of the flow rate. For 'type A' and 'type B' sensors that are both power supplied with DC 5 V, the sensitivities are sequentially measured as 766.80 mV (µL s-1)-1 and 19.12 mV (µL s-1)-1, with the nonlinearities as 0.4% FS and 0.9% FS, respectively. Compared with traditionally fabricated micro flow sensors, the single-chip fabricated differential-pressure flow sensors can be low-cost volume manufactured. Moreover, the bare sensor chips can be simply SMT packaged for low-cost micro-system applications. [ABSTRACT FROM AUTHOR]

A single-side processed dual-cantilever high-shock accelerometer in (111) silicon wafers is proposed in this paper. The device is formed by using advanced silicon surface and bulk micromachining technologies, including deep-reactive ionic etch and lateral under-etching structural release. Because the sensor is fabricated in (111) silicon wafer and has a single-chip single-side structure, it facilitates simple post-packaging, reduced device dimension, and low cost mass production. The controllable gap distance between the bottom surface of the cantilever and the substrate can be used for restraining cross-sensitivity of orthogonal direction. The performance of the accelerometer is examined by using a free dropping hammer system. The results of the shock test show the acceleration sensitivity of 0.71 \mu\Vg^-1 for a 20 500 g shock acceleration under 3.3 V power supply and the resonant frequency of 79 kHz. The zero-point offset temperature drift of the sensor is 89 \ppm/^\circ\C within the temperature range of -20\ ^\circ\C to 120 ^\circ\C. \hfill[2010-0048] [ABSTRACT FROM AUTHOR]

Abstract: Two kinds of integrated scanning probe microscope (SPM) probes are developed. The first kind is AFM probes realized with a novel masked–maskless combined etching process. Both the nano-tips for scanning and the bending cantilevers are simultaneously formed with the masked–maskless combined anisotropic etching technique. The simultaneous formation method effectively avoids damage to the previously formed tips when the cantilever shaping is processed. The testing results for the probes show the imaging quality comparable with commercial probes. The second kind of probes is an integrated probe with both a piezoresistive sensor and an electric-heated tip. This kind of probe is used for thermal–mechanical data storage, with the pulse-heated tip for data writing and the piezoresistive sensor for data reading. Nano-sized bumps have been formed by probe scanning on PMMA thin film, resulting in a storage density beyond 30GB/in.2. [Copyright &y& Elsevier]

Abstract: A micromachined piezoresistive cantilever magnetometer, with a self-calibration function on-chip integrated is presented . When the cantilever is subjected to a magnetic field to be measured, the magnetic force will exert upon the magnetized nickel thin-film pattern that is located at the cantilever end. The magnetic force bends the micromechanical cantilever, which is further read out by an integrated piezoresistor. For realizing the self-calibration function, an aluminum spiral is integrated around the cantilever to provide an artificial magnetic field, when an electric current flows through the spiral coil. The artificial magnetic field can be used to drive the cantilever bending and causes a self-calibration output signal. With this on-chip self-calibration scheme, the detection of magnetic field can be immune to the long-term drift in remanence of the magnetized nickel pattern, thereby, improving the sensing stability. Bulk micromachining technologies are used to fabricate the sensors. The formed sensor is used for magnetic-field measurement, resulting in the piezoresistive sensitivity as 1.06×10−4/mT and the sensing resolution 4.58μT. [Copyright &y& Elsevier]

A strong mechanical coupling scheme between two degrees of freedom (2-DOF) is proposed in this paper for resonance enhancement of silicon micromachined resonators. Two spring-mass-damping resonant units, with identical (or close) resonant frequency and great disparity in mass, are mechanically linked together to form a 2-DOF resonator. When the big unit (with bigger mass) is driven to resonate, a much-enlarged resonant amplitude of the small unit (with smaller mass) can be obtained, attributed to the strong mechanical coupling between the two units. PSPICE is used for simulation of the properties of the strong mechanical coupling effect. The simulation fairly verifies the mechanical coupling modeling of 2-DOF resonators and, furthermore, analyzes the effect of quality factor, which is dominated by damping, on the enlarged resonant amplitude, ratio of resonant amplitude between the two units, resonant frequency drift and resonant phase deviation. An ultra-thin silicon cantilever-shaped 2-DOF resonator consisting of a wide base-cantilever and a narrow working cantilever is fabricated with a high yield process. The 2-DOF resonator is driven in vacuum with incident laser light on the wide base cantilever. The resonant amplitude is detected with laser Doppler meter. Measurement results agree well with the strong mechanical coupling modeling of 2-DOF resonators. [Copyright &y& Elsevier]

Monolithic integration of micromechanical composite sensors needs to fabricate multiple levels of three-dimensional (3-D) microstructures to satisfy individual requirements from individual on-chip sensing elements. Meanwhile, volume fabrication of the composite sensors is needed in many applications that prefer single-sided process in low-cost non-silicon-on-insulator single wafer. A novel single-sided micromachining technique is herein proposed and developed to form such multilevel 3-D structures, where only integrated-circuit (IC) foundry available processes are used, i.e., neither double-sided process nor wafer-bonding is used. With the IC-foundry compatible micromachining process, a six-level 3-D microstructure has been successfully formed for tire-pressure monitoring system (TPMS) sensors. Benefited from the single-side process and the namely pressure-sensor in accelerometer (PinG) dual-sensor architecture, the single-wafer-based dual-sensor features a tiny chip size of 1.25 mm $\times $ 1.25 mm $\times$ 0.45 mm. Supplied with 3.3 V, 0.1-mV/kPa sensitivity for the 500-kPa-ranged pressure sensor and 0.05-mV/g sensitivity for the 120-g-ranged accelerometer are measured. By freely suspending the pressure-sensor structure from the stress-free mass end, the influence of acceleration to the pressure sensor is well eliminated, which was the main problem of the previous PinG sensors. Besides the achieved high-performance TPMS dual sensor, the IC-foundry manufacturable technique for multilevel 3-D microelectromechanical systems (MEMS) structures can be widely used in various monolithic MEMS devices. [2015-0034] [ABSTRACT FROM AUTHOR]

This study reports an oven-controlled microelectromechanical systems oscillator with integrated micro-evaporation trimming that achieves frequency stability over the industrial temperature range and permanent frequency trimming after vacuum packaging. The length-extensional-mode resonator is micro-oven controlled and doped degenerately with phosphorous to achieve a frequency instability of ±2.6 parts per million (ppm) in a temperature range of −40 to 85 °C. The micro-evaporators are bonded to the resonator, integrated face-to-face, and encapsulated in vacuum. During trimming, the micro-evaporators are heated electrically, and the aluminum layers on their surfaces are evaporated and deposited on the surface of the resonator that trims the resonant frequency of the resonator permanently. The impact of the frequency trimming on the temperature stability is very small. The temperature drift increases from ±2.6 ppm within the industrial temperature range before trimming to ±3.3 ppm after a permanent trimming of −426 ppm based on the local evaporation of Al. The trimming rate can be controlled by electric power. A resonator is coarse-trimmed by approximately −807 ppm with an evaporation power of 960 mW for 0.5 h, and fine-trimmed by approximately −815 ppm with an evaporation power of 456 mW for 1 h. Though the Q-factor decreases after trimming, a Q-factor of 304,240 is achieved after the trimming of −1442 ppm. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports a novel method to enhance solder ball or solder ring bonding strength by using electrowetting-on-dielectric (EWOD) effect. With a low melting point, the metal Sn has been widely used in electronic packaging technology. Since Sn will be molten into liquid when the temperature is increased above the melting point, the method for treating liquid can be herein employed. Contact angle of the molten Pb-free balls or ring structure on silicon substrate have been experimentally changed by applying electric field across the thin dielectric film between the molten solder and the conductive silicon substrate. The contact area between the solder and the substrate is enlarged due to the decrease of the contact angle. Our testing results on the EWOD enhanced packaging structures of solder balls, flip-chip and solder ring hermetic package generally show about 50% enhancement in bonding shear strength. The significantly enhanced solder link bonding strength is hopeful for improving packaging reliability and is promising to be used in high performance silicon based electronic or microelectromechanic SiP (system in package) technologies. [Copyright &y& Elsevier]

Abstract: To enhance the stability of packaged high-g MEMS accelerometers with double cantilevers positioned asymmetrically, the dynamic shock responses of components versus impurity concentration of piezoresistors at various working temperatures have been probed by using Finite Element Method (FEM). Results indicate that the dynamic output responses of component are actually the superposition of the forced vibrations with dynamic shock and those of cantilevers in their eigenfrequency. The dynamic responses of components are sensitive to the working temperature. With the increase of working temperature, the inherent frequency vibrations of the cantilevers are depressed gradually. Moreover, the larger the difference between the working temperature and reference temperature, the more obvious the impurity effect of piezoresistors is. The difference between the peak output voltage of response under 1×1018 cm−3 and that under 1×1021 cm−3 varies greatly from −2.2146mV at T =0°C to 8.6609mV at T =100°C, of course, is partly due to the characteristic variation of damping media under various working temperatures. Therefore, to improve the stability of component and further weaken the impurity concentration effect and the temperature effect of piezoresistors on the performance of components, it is necessary to increase the impurity concentration of piezoresistors and keep the components working at relatively lower temperature only if the electro-performance of component is satisfied. [Copyright &y& Elsevier]

Abstract: A simplified, cost-effective flexible micro-electronic-mechanical systems (MEMS) technology has been developed for realizing a temperature-sensing array on a flexible polyimide substrate. The fabrication technique utilized liquid polyimide to form flexible film on the rigid silicon wafer using a temporary carrier during the fabrication. The platinum thin film is employed as temperature sensitive material and 8×8 temperature-sensing arrays were micromachined on the polyimide, from which the silicon wafer carrier was removed at the end of fabrication. The platinum thin film temperature sensor exhibits excellent linearity and its temperature coefficient of resistance reaches 0.00291°C−1. Because of the effective thermal isolation, the flexible temperature sensors show a high sensitivity of 1.12Ω/°C at 10mA to the constant drive current. The flexible MEMS technology based on liquid polyimide enables the development of flexible, compliant, robust, and multi-modal sensor skins for many other important applications, such as robotics, biomedicine, and wearable microsystems. [Copyright &y& Elsevier]

• The composite FG-HKUST-1 was used as a stationary phase for the μGCC. • The μGCC can effectively separate light hydrocarbon mixtures (C 1 -C 4) with a resolution of 9.2 for methane and ethane. • The difference in the retention time between methane and ethane was 1.11 min. • The retention factor of ethane and the resolution of methane and ethane were increased by 166 % and 114 %. A composite material was synthesized at room temperature by performing modification of the copper benzene-1,3,5-tricarboxylate (HKUST-1) metal-organic framework material by multilayer fluorinated graphene (FG). The FG-HKUST-1 composite was used as a stationary phase for a micro gas chromatography column (μGCC) fabricated using micro-electro-mechanical system (MEMS) technology. The separation results showed that the μGCC with the FG-HKUST-1 composite stationary phase achieved a baseline separation of C 1 -C 4 in 8 min. The retention factors for C 2 -C 4 were 2.13, 7.14, and 12.04, respectively. The maximum relative standard deviation (RSD) of the retention times was 0.14 %. The difference in the retention time between methane and ethane was 1.11 min, with a resolution of 9.2 for methane and ethane. The retention factor of ethane and the resolution of methane and ethane were increased by 166 % and 114 %. Therefore, this μGCC is promising for separating light hydrocarbons with widely differing concentrations. [ABSTRACT FROM AUTHOR]

Highlights • A ±500-ppb stability oven-controlled N++ [100] silicon resonator over the industrial temperature range is presented. • Electrical isolation anchors are designed to keep the sensitivity stable and achieve a uniformly- heated micro-heater. • A heating-voltage controlled algorithm based on two-point linear fitting method for heating power is built. Abstract In this paper, we demonstrate that a uniformly heated oven-controlled N++ [100] length-extensional-mode silicon resonator with ± 500 ppb frequency stability can be achieved over the temperature range of −40 °C to 85 °C. Electrical isolation anchors, with an insulation layer between the resonator and the heating beams, are designed to separate the heating and excitation voltages of the Wheatstone half-bridge. Owing to the constant bridge voltage applied to the resonator, the sensitivity can be kept stable at different ambient temperatures. Because the heating current does not pass the resonator with self-heating inhibition, the resonator is uniformly heated, by conductance heat from the heating beams, to the turnover temperature at which the temperature coefficient of the resonant frequency is equal to zero. In addition, it is demonstrated that the open-loop control algorithm, based on the thermoresistor on the substrate and the two-point linear-fitting method for heating power versus chip temperature, is sufficiently accurate for achieving high-frequency stability over the industrial temperature range. [ABSTRACT FROM AUTHOR]

In this paper, a novel embeded elliptic cylindrical posts (ECPs) with large surface area and wide effective width, which could support more stationary phase and decrease the pressure drop, is applied on the micro-fabricated gas chromatographic (μGC) column. Compared with μGC column with cylindrical posts (CPs), the surface area and effective width of μGC column with ECPs are increased by 29% and 30%. Separation experiments are performed under the same head pressure at column inlet: in experiments of separating mixture 1, the column efficiency of the μGC column with ECPs for C9 has a 76% improvement, and the separation resolution between C8 and C9 also has a 34% improvement; in experiments of separating mixture 2, seven kinds of analytes can be identified by the μGC column with ECPs less than ten minutes, while, only six kinds can be identified by the μGC column with CPs in almost the same time. In detail, the column efficiency of the μGC column with ECPs for toluene has a 129% improvement, and the separation resolution between benzene and toluene also has a 56.4% improvement. Hence, the μGC column with the inner structures of ECPs is a valid means to improve column efficiency and resolution in a lower pressure drop. [ABSTRACT FROM AUTHOR]

Microfabricated semi-packed gas chromatography (GC) columns coated with two kinds of mesoporous silica (MS) stationary phase have been explored and compared in this paper. The micro GC (μGC) columns are fabricated by microelectromechanical system (MEMS) technique. MSs with pore size of 2 and 5 nm are prepared using two different soft-templates and deposited on the inner surface of the μGC columns by dip-coating. For the first time, the influence of pore size of MS stationary phase on the separation performance in a μGC column has been investigated. As demonstrated, the mixtures of light alkanes (C1–C4) or heavy alkanes (C5–C10) can be well separated in both columns, where the separation resolution is always higher than 1.25 except for C1–C2 and C5–C6. Considering the pore size effect on the separation performance, it is shown that analytes, especially those with bigger size, display longer retention time in the column with larger pore size. For C10, the retention time in 5 nm-MS column is 200% longer than that in 2 nm-MS one. [ABSTRACT FROM AUTHOR]

High performance NH 3 sensor is of great importance in various application fields such as environmental protection and early diagnosis of stomach cancer. Herein, carboxyl group functionalized mesoporous silica nanoparticles (C-MSNs) with ultrahigh specific surface area are developed as high performance mass-type sensing material for trace-level NH 3 detection. By using inkjet printing technology, C-MSNs material is precisely loaded on our lab-made integrated resonant microcantilever to construct a mass-type gas sensor. Based on the specific acid-base interaction between Brønsted acidic C-MSNs material and basic NH 3 molecules, our sensor exhibits satisfactory NH 3 sensing performance. The experimentally observed detection limit of our sensor reaches parts per billion (ppb) level. Exposed to NH 3 with identical concentration, our sensor outputs a higher response in wet air than that of in dry atmosphere. In real air, hydrate NH 3 molecule ( i.e. NH 3 · x H 2 O) has a larger molecular weight than anhydrous NH 3 in absolute dry experimental atmosphere. Therefore, our gravimetric sensor exhibits a higher response in real air. In order to in-depth elucidate the humidity-enhanced sensing effect, the micro-gravimetric sensing data obtained in wet air and in dry experimental environment are compared together. Based on our quantitatively measurement data, the molecular formula of hydrate NH 3 · x H 2 O existing in wet air (with 50–80% relative humidity) can be obtained as NH 3 ·2∼2.4H 2 O. [ABSTRACT FROM AUTHOR]

In this paper, an electrostatic vibration energy harvester is proposed and fabricated with both broad bandwidth and high normalized power density (NPD, harvested power/volume/acceleration 2 ). The device is made up of two parts, top movable plate and bottom fixed plate, both of which are fabricated from silicon wafers using advanced micro-electro-mechanical system (MEMS) technology. A CYTOP polymer layer is spray coated for an electret material as well as an adhesive layer for low temperature wafer bonding. The air damping effect in energy harvesting has been investigated. At a low pressure of 3 Pa in a vacuum chamber, maximum power output of 4.95 μW has been harvested at low vibration amplitude of 0.09 g, resulting in a bandwidth of 12 Hz and NPD of 3 mW/cm 3 /g 2 , which outperforms most of the previous harvesters. A high harvester effectiveness of 67.9% is therefore achieved. The response on random vibrations is also tested. An average output power of 2.22 μW is harvested when random vibration is applied at a frequency range of 160 ± 12.5 Hz with RMS acceleration of 10.5 m/s 2 . The excellent overall performance gives promising application for energy harvesting from random sources and multi-device stack for wireless sensor networks. [ABSTRACT FROM AUTHOR]

• The LBL deposition process improved the uniformity of the stationary phase and the separation performance of C1–C4. • The resolutions and symmetries of C1–C4 were improved upon increasing the number of deposition cycles. • The resolution of C1–C2 was as high as 5.89 after 8 deposition cycles. • The tailing factors of C1–C4 were closest to 1 after 8 deposition cycles. In this paper, a micro gas chromatographic column (μGCC) was fabricated via the layer-by-layer (LBL) deposition of mesoporous silica (MS) as the stationary phase. The μGCC with embedded elliptical-cylindrical posts was fabricated by typical micro-electro-mechanical system (MEMS) techniques. The MS powder was prepared by a sol-gel method and then deposited inside the microchannels of the μGCC by LBL deposition. This process avoided the high temperature required for the sol-gel method to directly prepare MS inside the microchannel surfaces of the μGCC. Mixtures of light alkanes (C1–C4) could be separated in the μGCC. The separation results showed that the resolution between the components of the sample increased with the number of deposition cycles. When the number of deposition cycles increased from 1 to 8, the resolution of methane and ethane was increased from unseparated to 5.89. [ABSTRACT FROM AUTHOR]

This study presents ‘dog-bone’ structured bulk-mode resonant gas sensors that can be low-cost volume fabricated in standard IC foundries. Without the need for MEMS-specific processes like double-side aligned photolithography and wafer-to-wafer bonding, the sensor fabrication can be completed in standard IC-foundries, thereby showing advantage in low-cost mass production and application. Based on a diaphragm-on-cavity structure made by a MIS (micro-openings inter-etch and sealing) micromachining technology in ordinary (non-SOI) single-wafer, the resonator fabrication is further completed with simple dry etching and metal interconnection. With similar fabrication scheme to semiconductor IC chips, herein the 3-D micromachining processes are only implemented from the front-side of the wafer (with unpolished wafer backside) and all the fabrication steps utilize IC-foundry available processes. After loading with gas sensitive material, the resonant sensors are ready for application. For comparison, traditional sensors with identical resonator structure are also fabricated in SOI wafer with double-sided process. Besides the measured similar resonance performance for the two sensors, the new sensor is advantageous in smaller dimensions (0.5 mm × 0.5 mm) and much lower volume-fabrication cost (in ASMC, a 6-inch IC foundry company in Shanghai) of one US-cent per sensor. By loading an organo-phosphor sensitive chemical-group modified hyper-branched polymer onto the new resonator, the disposable biochemical micro-sensor is used to rapidly detect organophosphorous pesticide residue for food-safety and agriculture applications. The resonant chemical sensor experimentally performs linear and repeatable detection of ppm -level organo-phosphorous vapor. [ABSTRACT FROM AUTHOR]

• A semi-packed column with high-density elliptic cylindrical posts was developed. • The surface area of SC HECP is 71% larger than SC CP. • The aspect ratio of SC HECP is 76% larger than SC CP. • Higher surface area and aspect ratio leads to better performance. Semi-packed columns are microfabricated gas chromatography columns which have a large surface area and high aspect ratio. In this paper, a new semi-packed column with high-density elliptic cylindrical posts (SC HECP) made by a micro-electro-mechanical system (MEMS) technique was reported. Compared to a semi-packed column with cylindrical posts (SC CP) under the same effective width, the surface area and aspect ratio of SC HECP were improved by 71.19% and 76.47%, respectively. To compare the performance of these two semi-packed columns, SC HECP and SC CP were fabricated. A 10-nm thick alumina film was deposited as the stationary phase by atomic layer deposition technique to ensure the uniformity and repeatability of the stationary-phase film. A contrast experiment was conducted, and the results showed that compared with SC CP, better separation performance was realized in SC HECP due to the increase in surface area and aspect ratio. The number of theoretical plates of nonane was increased by 541.84%, and the tailing factor was decreased by 54.31%. [ABSTRACT FROM AUTHOR]

Abstract: A novel surface-micromachining technology is developed to monolithically integrate piezoresistive pressure sensor and accelerometer for tire-pressure monitor system (TPMS) applications. A narrow rectangular diaphragm piezoresistive pressure sensor and a clamped beam-mass piezoresistive accelerometer compose the monolithic composite sensor that are on-chip integrated in a 1.6mm×1.6mm single chip for low-cost production. With an electroplated Cu seismic-mass, the sensitivity of the accelerometer is much improved so that it can be compatibly fabricated with the pressure sensor by using surface-micromachining processes. For facilitating on-chip known-good-die and reliable TPMS application, the electroplated metal mass is used as a versatile structure to realize electrostatic self-testing function for the accelerometer. The fabricated TPMS sensors are characterized, resulting in 83.6mV/MPa/3V sensitivity and 0.34% FSO linearity for the 450kPa-ranged pressure sensor, as well as, 15.6μV/g/3V sensitivity for the 125g-ranged accelerometer. In addition, the on-chip electrostatic self-testing function is experimentally validated for the accelerometer. [Copyright &y& Elsevier]

Abstract: A dynamic collision model is proposed and built to analyze over-range protection of cantilever beam–mass structured micro-accelerometers. The model encloses angular momentum of the seismic mass, squeeze-film air damping, inertial force and supporting force (acting at the cantilever-root) during the collision between the seismic mass and the over-range stopping bumpers. Based on angular momentum balance equation we obtain the relationship among the supporting force F, the collision time duration t and the rotation center c where the bumpers are located. In the best case of F=0 which means no supporting force acts on the cantilever, we find the optimal bumper location of c. The accelerometers have been fabricated with the over-range protection design according to the dynamic collision model. Experimental test shows that 5g measure-range accelerometers can endure 9000g acceleration and there is no sign of performance degradation, which well verified the dynamic collision model. [Copyright &y& Elsevier]

Abstract: Reliable and accurate pick and release of microobjects is a long-standing challenge at the microscale manipulation field. This paper presents a new hybrid type of microelectromechanical systems (MEMS) microgripper integrated with an electrostatic mechanism and vacuum technology to achieve a reliable and accurate manipulation of microobjects. The microgripper is fabricated by a surface and bulk micromachining technology. Vacuum pipelines are constructed by bonding technique. The pick and release micromanipulation of microobjects is accomplished by electrostatic driving force caused by comb structure and an auxiliary air pressure force from air pump. A deflection of 25μm at the tip of the gripper is achieved with the applied voltage of 80V. The performance of this new hybrid type of microgripper was experimentally demonstrated through the manipulation of 100–200μm polystyrene balls. Experimental results show that this microgripper can successfully fulfil the pick and release micromanipulation. Theoretical analyses were conducted to have a more comprehensive understanding of the release principle. Based on this paper, the new kind of hybrid microgripper will possibly provide an effective solution to the manipulation of submicrometer-sized objects. [Copyright &y& Elsevier]

Presented in this paper, is a shock accelerometer fabricated by silicon micromachining technology. The accelerometer is constructed with an iso-width twin-mass-plate structure that can greatly increase the natural frequency and facilitate the fabrication process. Theoretical analysis and ANSYS simulation of the structure show that it can cover a wide range from 2,000g to 200,000g depending on the thickness of the plate if packaged successfully. The primary performance of the accelerometer was examined using a free dropping-bar system. Experimental results on sensitivity and resonance frequency are presented and compared with the theoretical values. The results of the shock tests show that the accelerometer with a plate thickness of 74 μm has a sensitivity of 1.43 μV g−1 under 5 V excitation, and its resonance frequency is greater than 200 kHz. [Copyright &y& Elsevier]