Microelectromechanical Systems Process Research Articles

A Novel PZT Pump with Built-in Compliant Structures.

Different to the traditionally defined valved piezoelectric (PZT) pump and valveless PZT pump, two groups of PZT pumps with built-in compliant structures—with distances between the free ends of 0.2 mm (Group A) and 0 mm (Group B)—were designed, fabricated, and experimentally tested. This type of pump mainly contains a chamber 12 mm in diameter and 1.1 mm in height, a PZT vibrator, and two pairs of compliant structures arranged on the flowing channel. The flow-resistance differences between these two groups of PZT pumps were theoretically and experimentally verified. The relationships between the amplitude, applied voltage and frequency of the PZT vibrators were obtained experimentally, with results illustrating that the amplitude linearly and positively correlates with the voltage, while nonlinearly and negatively correlating to the frequency. The flow rate performance of these two groups was experimentally tested from 110–160 Vpp and 10–130 Hz. Results showed that the flow rate positively correlates to the voltage, and the optimum flow rate frequency centers around 90 Hz for Group A and 80 Hz for Group B, respectively. The flow rate performances of Group B were further measured from 60–100 Hz and 170–210 Vpp, and obtained optimal flow rates of 3.6 mL/min at 210 Vpp and 80 Hz when ignoring the siphon-caused backward flow rate. As the compliant structures are not prominently limited by the channel’s size, and the pump can be minimized by Micro-electromechanical Systems (MEMS) processing methods, it is a suitable candidate for microfluidic applications like closed-loop cooling systems and drug delivery systems.

The Effects of Cold Arm Width and Metal Deposition on the Performance of a U-Beam Electrothermal MEMS Microgripper for Biomedical Applications.

Microelectromechanical systems (MEMS) have established themselves within various fields dominated by high-precision micromanipulation, with the most distinguished sectors being the microassembly, micromanufacturing and biomedical ones. This paper presents a horizontal electrothermally actuated ‘hot and cold arm’ microgripper design to be used for the deformability study of human red blood cells (RBCs). In this study, the width and layer composition of the cold arm are varied to investigate the effects of dimensional and material variation of the cold arm on the resulting temperature distribution, and ultimately on the achieved lateral displacement at the microgripper arm tips. The cold arm widths investigated are 14 m, 30 m, 55 m, 70 m and 100 m. A gold layer with a thin chromium adhesion promoter layer is deposited on the top surface of each of these cold arms to study its effect on the performance of the microgripper. The resultant ten microgripper design variants are fabricated using a commercially available MEMS fabrication technology known as a silicon-on-insulator multi-user MEMS process (SOIMUMPs)™. This process results in an overhanging 25 m thick single crystal silicon microgripper structure having a low aspect ratio (width:thickness) value compared to surface micromachined structures where structural thicknesses are of the order of 2 m. Finite element analysis was used to numerically model the microgripper structures and coupled electrothermomechanical simulations were implemented in CoventorWare. The numerical simulations took into account the temperature dependency of the coefficient of thermal expansion, the thermal conductivity and the electrical conductivity properties in order to achieve more reliable results. The fabricated microgrippers were actuated under atmospheric pressure and the experimental results achieved through optical microscopy studies conformed with those predicted by the numerical models. The gap opening and the temperature rise at the cell gripping zone were also compared for the different microgripper structures in this work, with the aim of identifying an optimal microgripper design for the deformability characterisation of RBCs.

Investigation of Micromachined Antenna Substrates Operating at 5 GHz for RF Energy Harvesting Applications.

This paper investigates micromachined antenna performance operating at 5 GHz for radio frequency (RF) energy harvesting applications by comparing different substrate materials and fabrication modes. The research aims to discover appropriate antenna designs that can be integrated with the rectifier circuit and fabricated in a CMOS (Complementary Metal-Oxide Semiconductor)-compatible process approach. Therefore, the investigation involves the comparison of three different micromachined antenna substrate materials, including micromachined Si surface, micromachined Si bulk with air gaps, and micromachined glass-surface antenna, as well as conventional RT/Duroid-5880 (Rogers Corp., Chandler, AZ, USA)-based antenna as the reference. The characteristics of the antennas have been analysed using CST-MWS (CST MICROWAVE STUDIO®—High Frequency EM Simulation Tool). The results show that the Si-surface micromachined antenna does not meet the parameter requirement for RF antenna specification. However, by creating an air gap on the Si substrate using a micro-electromechanical system (MEMS) process, the antenna performance could be improved. On the other hand, the glass-based antenna presents a good S11 parameter, wide bandwidth, VSWR (Voltage Standing Wave Ratio) ≤ 2, omnidirectional radiation pattern and acceptable maximum gain of >5 dB. The measurement results on the fabricated glass-based antenna show good agreement with the simulation results. The study on the alternative antenna substrates and structures is especially useful for the development of integrated patch antennas for RF energy harvesting systems.

Low-Cost, High-Performance Fiber Optic Fabry⁻Perot Sensor for Ultrasonic Wave Detection.

This study describes a novel fiber optic extrinsic Fabry–Perot interferometric (EFPI) ultrasonic sensor comprising a low-cost and high-performance silicon diaphragm. A vibrating diaphragm, 5 μm thick, was fabricated by using the Microelectromechanical Systems (MEMS) processing technology on a silicon-on-insulator (SOI) wafer. The Fabry–Perot (FP) cavity length was solely determined during the manufacturing process of the diaphragm by defining a specific stepped hole on the handling layer of the SOI wafer, which made the assembly of the sensor easier. In addition, the use of cheap and commercially available components and MEMS processing technology in the development of the sensing system, limited the cost of the sensor. The experimental tests showed that the minimum detectable ultrasonic pressure was 1.5 mPa/sqrt(Hz) −0.625 mPa/sqrt(Hz) between 20 kHz and 40 kHz. As a result, this sensor has the potential to successfully detect weak ultrasonic signals.

A Valveless Piezoelectric Micropump Based on Projection Micro Litho Stereo Exposure Technology

At present, the micropumps are usually adopted in microelectromechanical systems (MEMS) process, which is characterized by high technical complexity and expense, to obtain micro-scale internal channels. Moreover, the MEMS process is more suitable for the 2.5-dimensional channels. This paper presents a 3-dimensional vortex tube-based valveless piezoelectric micropump with low cost and high accuracy, and the projection micro litho stereo exposure (PμLSE) technology is applied to manufacture the prototype of the micropump. The working principle of the piezoelectric micropump is analyzed, and the flow resistance of the vortex diode is calculated numerically. Then, the performance and 3D morphology measurement of the micropump are conducted. The results demonstrate that the inner surface of the channel is uniform and the surface roughness is small. By comparing and analyzing the output performances between two prototypes manufactured by the PμLSE technology, the stability of the PμLSE technology is confirmed. This paper provides a fast and cheap method for manufacturing a 3D micropump, and the proposed approach can also be further adopted in fabricating such micro-stereoscopic structure devices.

Omnidirectional Solid Angle Beam-Switching Flexible Array Antenna in Millimeter Wave for 5G Micro Base Station Applications

This study proposes a cylindrical conformal array antenna (CCAA) for fifth-generation (5G) micro base station applications. The CCAA is composed of five Chebyshev flexible linear array antennas (LAAs) with a circumferentially uniform arrangement on the cylindrical surface. The LAA with a logarithmic periodic arrangement is constructed by synthesizing the current amplitude distribution coefficients in elements with the Chebyshev method. The LAA with a half-power bandwidth (HPBW) wider than 76° (−8.41° to 38.58°) and a peak gain greater than 10 dBi is fabricated via the micro-electromechanical system process. Cost–performance analysis shows that five is the best number of linear arrays. To achieve omnidirectional switching scanning of the circumferential section, five LAAs wrapped on the cylindrical surface are individually excited by connecting a radio frequency semiconductor switch to the exciting ports of an eight-way power divider. Moreover, beam-switch scanning of the CCAA is measured with the aid of a standard anechoic chamber. The irradiated performance with low mutual coupling and high realized gain is verified to be irrelevant to the structural variation of various flexible experiments of LAAs wrapped around a cylindrical surface. The CCAA with beam-switch scanning operates at 26 GHz and belongs to the 5G millimeter-wave band. Results show the proposed antenna achieves omnidirectional scanning property in the H plane and has a HPBW of only 9.08° in the E plane. The performances of the CCAA present potential advantage in flexible terminal equipment wireless communication.

Explosion Suppression Mechanism Characteristics of MEMS S&A Device With In Situ Synthetic Primer.

The traditional silicon-based micro-electro-mechanical systems (MEMS) safety and arming (S&A) device fuze cannot isolate abnormal outputs in the detonation environment, which creates hazards for personnel. To address this problem, we report the design of a MEMS S&A device with integrated silver, copper, nickel and polyimide (PI) films, which is based on the principle of a MEMS S&A device and uses copper azide as the primer. The MEMS S&A device was optimized using theoretical calculations of the explosion suppression mechanism performance in a detonation field, where the theoretical model was verified by dynamic simulation (LS-Dyna). Silicon-based MEMS processing technology was used to integrate the MEMS S&A device with energy-absorbing materials, and the device performance was compared in detonation tests. Silicon-based MEMS S&A devices with silver, copper, nickel, and PI (100-μm-thick) achieved a reliable explosion suppression mechanism capability when exposed to a detonation wave. The residual stress was measured using Raman microscopy, and the PI film exhibited the best explosion suppression mechanism performance of the four materials. A reliability test to determine the maximum explosion suppression mechanism dose for a MEMS S&A device attached to a PI film (100-μm-thick) showed that the maximum amount of primer needed for the effective explosion suppression mechanism capability on the MEMS S&A device was 0.45 mg.

Room-Temperature Sensing of Single Electrons Using Vibrating-Reed Electrometer in Silicon-on-Glass Technology

In the commonly used existing silicon-on-insulator microelectromechanical systems (MEMS) process, a silicon-oxide-silicon sandwich structure in the sensor device creates parasitic capacitance, which reduces the charge sensitivity. In this letter, for the first time, we demonstrate a vibrating-reed-based electrometry system with high sensitivity and resolution in the silicon-on-glass (SOG) MEMS process. In this letter, we utilize a glass substrate instead of silicon to ameliorate charge sensitivity by reducing the parasitic capacitance. An improved preamplifier circuit topology incorporating with the proposed sensor shows a sensitivity of $1.43\times 10^{\textsf {11}}$ V/C, which is the highest in the literature. In addition, the best charge resolution of 1.03 e/ $\surd $ Hz@5.7 kHz has achieved at room temperature and atmospheric pressure. This result provides strong evidence for the validity of our SOG-based MEMS device as a charge sensor for detecting even a single electron.

Piezoresistive temperature sensors fabricated by a surface micromachining CMOS MEMS process

This paper presents a micromachined monocrystalline silicon piezoresistive temperature sensor fabricated by a surface micromachining CMOS (Complementary Metal Oxide Semiconductor) MEMS (Micro-Electro-Mechanical System) process. The design of the temperature sensor is based on the structure of the multi-layer cantilever beam and the bimetallic effect. The temperature change of the cantilever beam is translated into the change of the piezoresistance’s value. The test results show that the sensitivities of the sensors are 27.9 mV/°C with 100 Ω/▯ piezoresistance between −40 °C to 60 °C and 7.4 mV/°C with 400 Ω/▯ piezoresistance between −90 °C to 60 °C. The temperature sensor proposed in this paper can be used in radiosondes for its low operating temperature (as low as −90 °C), small size (below 1 mm2) and low heat capacity.

Design of tunable interdigital capacitor

In this paper, a MetalMUMPs (Multi-User Microelectromechanical System Processes) based tunable interdigitated capacitor is proposed. The tunable interdigitated capacitor consists of thermal actuator, guided beam, and twelve closely coupled parallel fingers lines to produce a nominal capacitance value of about 40.863 fF capable to tune till 326.902 fF. It actuated (tunned) thermally by applying a voltage across the thermal actuator to decreased distance between capacitor rotor and stator then capacitor becomes more capacitive, due to the increase in fringing fields between the fingers. The tunable interdigitated capacitor was fabricated on a standard low-resistivity substrate adopting MetalMUMPs manufacturing process. It was suspended by 25μm from the inner surface of the etched silicon substrate. It typical called microstrip tunable interdigitated capacitor. The capacitor was designed using 2008 CoventorWare software and fabricated based on MetalMUMPs technology. The measured capacitor structure is 494×520 μm2. The measured results show good compatible with theoretical one.

Flexible vibrational energy harvesting devices using strain-engineered perovskite piezoelectric thin films

The material properties of Pb(Zr,Ti)O3 (PZT) thin film with a LaNiO3 (LNO) buffer layer on an ultra-thin Ni-Cr-based austenitic steel metal foil substrate are systematically investigated for flexible piezoelectric vibrational energy harvesting device applications. The use of the flexible austenitic metal foil substrate with a high thermal expansion coefficient results in the large compressive stress in the deposited PZT thin film, and subsequently produces much enhanced ferroelectric polarization of the film. The measured polarization value of the PZT film on the flexible metal foil substrate is over 50 µC/cm2, showing a great improvement in comparison with the film on the conventional Pt/Ti/SiO2/Si substrate. Simultaneously, the LNO buffer layer prevents any undesirable reactions, provides uniform nucleation sites and promotes easy crystallization of the PZT thin film, achieving the highly dense and uniform microstructure of the film with a smooth surface. Using the strain-engineered PZT thin film, a small-scale and flexible vibrational energy harvester is fabricated using a simple punching process without any complex microelectromechanical system (MEMS) or etching processes. The maximum power and the corresponding peak voltage of the device are 5.6 µW and 690 mV, respectively, which are much higher values than those of MEMS-based vibrational energy harvester. The improved device performance of our flexible small-scale vibrational energy harvester is due to the enhanced PZT film properties by the stress engineering, the increased flexure and deflection of the flexible structure, and the easy vibrational sensitivity at low acceleration of 0.5g, compared to the MEMS-based device integrated with conventional Si-based substrates. The results prove that our strain-tuned PZT thin film-based flexible vibrational piezoelectric energy harvester is a promising candidate for autonomous power systems and future small-scale mobile platforms.

Photomechanical and Chemomechanical Actuation Behavior of Graphene-Poly(dimethylsiloxane)/Gold Bilayer Tube for Multimode Soft Grippers and Volatile Organic Compounds Detection Applications.

Graphene polymers-based soft actuators driven by infrared (IR) light have attracted wide attention recently. However, the scientific fraternity is striving hard in unraveling the area of actuators that could be triggered by IR light along with chemicals. The fabricating methodology of multiresponsive soft actuators based on graphene nanoplatelets (GNPs)-poly(dimethylsiloxane) (PDMS) nanocomposite/gold bilayers, ensuring large, fast, and reversible response, has been illustrated. The actuators display a novel dual-mode operation as photomechanical and chemomechanical actuation. The actuators are realized by depositing a thin film (100 nm) of gold on GNP-PDMS nanocomposite films resulting tubular structure on account of thermal residual stress. The actuation response of this structure upon its exposure to IR light and chemicals was measured in terms of percentage opening and degree of unscroll, respectively. The three-dimensional tubular structure is transformed into a two-dimensional sheet within 8 s under IR light irradiation. The same structures were also tested in various organic solvents like methanol, ethanol, acetone, isopropyl alcohol, and aldehydes, but the actuation has been observed only in acetone and aldehydes. This tubular actuator unscrolls completely and then scrolls in opposite direction along with tube axis shift through 90° during its exposure to acetone (liquid/vapors) and aldehydes. Few applications of these actuators, such as multimode soft grippers for on-demand capture/release of objects (with weight 1.2 times the actuator's own weight) and volatile organic compounds detection module, have been demonstrated. The combination of surface micromachining techniques of microelectromechanical systems process with this smart material may find applications in drug-delivery systems with precise control, soft robotics, and noninvasive diagnosis of diabetes and breast/lung cancers.

Accurate Measurements of Wall Shear Stress on a Plate with Elliptic Leading Edge.

A micro-floating element wall shear stress sensor with backside connections has been developed for accurate measurements of wall shear stress under the turbulent boundary layer. The micro-sensor was designed and fabricated on a 10.16 cm SOI (Silicon on Insulator) wafer by MEMS (Micro-Electro-Mechanical System) processing technology. Then, it was calibrated by a wind tunnel setup over a range of 0 Pa to 65 Pa. The measurements of wall shear stress on a smooth plate were carried out in a 0.6 m × 0.6 m transonic wind tunnel. Flow speed ranges from 0.4 Ma to 0.8 Ma, with a corresponding Reynold number of 1.05 × 106~1.55 × 106 at the micro-sensor location. Wall shear stress measured by the micro-sensor has a range of about 34 Pa to 93 Pa, which is consistent with theoretical values. For comparisons, a Preston tube was also used to measure wall shear stress at the same time. The results show that wall shear stress obtained by three methods (the micro-sensor, a Preston tube, and theoretical results) are well agreed with each other.

(Invited) Compact Telluride Films Prepared By Electrochemical Deposition and Their Applications for Integrated Micro- Thermoelectric Devices

Thermoelectric materials of Tellurium (Te) and its based compounds (binary Bi2Te3 and Sb2Te3, or ternary Bi2(TexSe1-x)3 and (BixSb1-x)2Te3) as the n-type and p-type materials, respectively), possess the best thermoelectric figure-of-merit in the temperature range of room temperature up to 200 °C. Preparing thick and compact Telluride films with thickness in the range of tens of micrometers by electrochemical deposition (ECD) allows to realize on-chip integration of thermoelectric devices. ECD offers additional advantages regarding up-scalability, cost effective processing, and compatibility with microelectromechanical systems processing. In our work, we firstly put efforts on growing thick and compact Telluride films for both n- and p- type materials by ECD technique. Secondly, various measurement techniques (in-situ and ex-situ) are utilized to characterize the thermoelectric transport properties, which are further analyzed to tune the ECD parameters to optimize the material properties. Thirdly, integrated micro- thermoelectric coolers (µTECs), with a leg pair packing density over 5000/cm2 are successfully fabricated by combining conventional techniques of ECD and photolithography. Long-term performance and stability of the as-fabricated µTECs are systematically studied using a CCD-based thermoreflectance imaging setup. Finally, model simulations based on finite-element method show consistency with the experimental results, indicating high quality thermoelectric materials (for both n and p legs) and negligible contact resistances in the as-fabricated µTECs.

The Effects of Structure Thickness, Air Gap Thickness and Silicon Type on the Performance of a Horizontal Electrothermal MEMS Microgripper

The ongoing development of microelectromechanical systems (MEMS) over the past decades has made possible the achievement of high-precision micromanipulation within the micromanufacturing, microassembly and biomedical fields. This paper presents different design variants of a horizontal electrothermally actuated MEMS microgripper that are developed as microsystems to micromanipulate and study the deformability properties of human red blood cells (RBCs). The presented microgripper design variants are all based on the U-shape ‘hot and cold arm’ actuator configuration, and are fabricated using the commercially available Multi-User MEMS Processes (MUMPs®) that are produced by MEMSCAP, Inc. (Durham, NC, USA) and that include both surface micromachined (PolyMUMPs™) and silicon-on-insulator (SOIMUMPs™) MEMS fabrication technologies. The studied microgripper design variants have the same in-plane geometry, with their main differences arising from the thickness of the fabricated structures, the consequent air gap separation between the structure and the substrate surface, as well as the intrinsic nature of the silicon material used. These factors are all inherent characteristics of the specific fabrication technologies used. PolyMUMPs™ utilises polycrystalline silicon structures that are composed of two free-standing, independently stackable structural layers, enabling the user to achieve structure thicknesses of 1.5 μm, 2 μm and 3.5 μm, respectively, whereas SOIMUMPs™ utilises a 25 μm thick single crystal silicon structure having only one free-standing structural layer. The microgripper design variants are presented and compared in this work to investigate the effect of their differences on the temperature distribution and the achieved end-effector displacement. These design variants were analytically studied, as well as numerically modelled using finite element analysis where coupled electrothermomechanical simulations were carried out in CoventorWare® (Version 10, Coventor, Inc., Cary, NC, USA). Experimental results for the microgrippers’ actuation under atmospheric pressure were obtained via optical microscopy studies for the PolyMUMPs™ structures, and they were found to be conforming with the predictions of the analytical and numerical models. The focus of this work is to identify which one of the studied design variants best optimises the microgripper’s electrothermomechanical performance in terms of a sufficient lateral tip displacement, minimum out-of-plane displacement at the arm tips and good heat transfer to limit the temperature at the cell gripping zone, as required for the deformability study of RBCs.

A cell culture device equipped with a micro-needle electrode array fabricated using backside exposure mold and resin casting.

A cell culture device equipped with a micro-needle electrode array was fabricated for the signal analysis of cell spheroids, cell masses, and cell sheets. For the analysis, sharp needle electrodes with a high aspect ratio for facilitating easy penetration into the cell mass and a small pitch for fine spatial resolution were required. Microelectromechanical systems (MEMS) technology is one of the common solutions for the fabrication of devices. However, an additional process, such as anisotropic etching or electro-polishing, is required for fabricating sharp needles. Tapered needles were fabricated using backside exposure for coating a layer of thick resist film on a glass substrate. The incident beam from mask apertures were diffracted and attenuated in the medium, resulting in tapered intensity distribution. A needle-like shape was obtained after performing resist development without using additional MEMS process. In this study, the theoretical analysis of optical intensity distribution and design and fabrication process of the device were described. Finally, the effectiveness of the device was evaluated by adding cultured cell mass on the needle array. Signals with spikes and fluctuations were observed in the electrode covered with cell mass, whereas only noise was observed on the non-covered electrode, demonstrating the signal pick-up ability of the device during cell culture.

High Dynamic Micro Vibrator with Integrated Optical Displacement Detector for In-Situ Self-Calibration of MEMS Inertial Sensors.

The scale factor drifts and other long-term instability drifts of Micro-Electro-Mechanical System (MEMS) inertial sensors are the main contributors of the position and orientation errors in high dynamic environments. In this paper, a novel high dynamic micro vibrator, which could provide high acceleration and high angular rate rotation with integrated optical displacement detector, is proposed. Commercial MEMS inertial sensors, including 3-axis accelerometer and 6-axis inertial measurement unit which is about 3 mm * 3 mm * 1 mm with 19 mg, could be bonded on the vibration platform of the micro vibrator to perform in-situ during the self-calibration procedure. The high dynamic micro vibrator is fabricated by a fully-integrated MEMS process, including lead zirconate titanate (PZT) film deposition, PZT and electrodes patterning, and structural ion etching. The optical displacement detector, using vertical-cavity surface-emitting laser (VCSEL) and photoelectric diodes (PD), is integrated on the top of the package to measure the 6-DOF vibrating displacement with the detecting resolution of 150 nm in the range of 500 μm. The maximum out-of-plane acceleration of the z-axis vibrating platform loaded with commercial 3-axis accelerometer (H3LIS331DL) achieves above 16 g and the maximum angular velocity achieves above 720°/s when the driving voltage is ±6 V.

Improving the Electrical Contact Performance for Amorphous Wire Magnetic Sensor by Employing MEMS Process.

This paper presents a novel fabrication method for amorphous alloy wire giant magneto-impedance (GMI) magnetic sensor based on micro electro mechanical systems (MEMS) technology. In this process, negative SU-8 thick photoresist was proposed as the solder mask due to its excellent properties, such as good stability, mechanical properties, etc. The low melting temperature solder paste was used for the electrical connections with the amorphous alloy wire and the electrode pads. Compared with the conventional welding fabrication methods, the proposed micro electro mechanical systems (MEMS) process in this paper showed the advantages of good impedance consistency, and can be fabricated at a low temperature of 150 °C. The amorphous alloy wire magnetic sensor made by the conventional method and by the micro electro mechanical systems (MEMS) process were tested and compared, respectively. The minimum resistance value of the magnetic sensor made by the conventional welding method is 19.8 Ω and the maximum is 28.1 Ω. The variance of the resistance is 7.559 Ω2. The minimum resistance value of the magnetic sensor made by micro electro mechanical systems (MEMS) process is 20.1 Ω and the maximum is 20.5 Ω. The variance of the resistance is 0.029 Ω2. The test results show that the impedance consistency by micro electro mechanical systems (MEMS) process is better than that of the conventional method. The sensor sensitivity is around 150 mV/Oe and the nonlinearity is less than 0.92% F.S.

Heat treatment effects on mechanical properties of Ni–Co alloy thin films

ABSTRACTVertical type probe is made by microelectromechanical system (MEMS) process in microscale for high degree of integration and performance. To design reliable probe before manufacturing, mechanical properties in microscale is needed. Also, manufactured probe is heat-treated to release residual stress. In this paper, to understand mechanical properties and heat treatment effect in microscale, tensile tests for Ni–Co alloy thin film is performed using specimen with heat-treated under air. The Ni–Co thin film has some enhanced mechanical properties by heat effect and becomes brittle. The changes of grain size distribution and grain direction are observed through electron back-scattered diffraction (EBSD).

Design, Fabrication, and Implementation of an Array-Type MEMS Piezoresistive Intelligent Pressure Sensor System.

To meet the radiosonde requirement of high sensitivity and linearity, this study designs and implements a monolithically integrated array-type piezoresistive intelligent pressure sensor system which is made up of two groups of four pressure sensors with the pressure range of 0–50 kPa and 0–100 kPa respectively. First, theoretical models and ANSYS (version 14.5, Canonsburg, PA, USA) finite element method (FEM) are adopted to optimize the parameters of array sensor structure. Combing with FEM stress distribution results, the size and material characteristics of the array-type sensor are determined according to the analysis of the sensitivity and the ratio of signal to noise (SNR). Based on the optimized parameters, the manufacture and packaging of array-type sensor chips are then realized by using the standard complementary metal-oxide-semiconductor (CMOS) and microelectromechanical system (MEMS) process. Furthermore, an intelligent acquisition and processing system for pressure and temperature signals is achieved. The S3C2440A microprocessor (Samsung, Seoul, Korea) is regarded as the core part which can be applied to collect and process data. In particular, digital signal storage, display and transmission are realized by the application of a graphical user interface (GUI) written in QT/E. Besides, for the sake of compensating the temperature drift and nonlinear error, the data fusion technique is proposed based on a wavelet neural network improved by genetic algorithm (GA-WNN) for average measuring signal. The GA-WNN model is implemented in hardware by using a S3C2440A microprocessor. Finally, the results of calibration and test experiments achieved with the temperature ranges from −20 to 20 °C show that: (1) the nonlinear error and the sensitivity of the array-type pressure sensor are 8330 × 10−4 and 0.052 mV/V/kPa in the range of 0–50 kPa, respectively; (2) the nonlinear error and the sensitivity are 8129 × 10−4 and 0.020 mV/V/kPa in the range of 50–100 kPa, respectively; (3) the overall error of the intelligent pressure sensor system is maintained at ±0.252% within the hybrid composite range (0–100 kPa). The involved results indicate that the developed array-type composite pressure sensor has good performance, which can provide a useful reference for the development of multi-range MEMS piezoresistive pressure sensor.