Microassembly platforms have attracted significant attention recently because of their potential for developing microsystems and devices for a wide range of applications.Despite their considerable poten-tial,existing ...Microassembly platforms have attracted significant attention recently because of their potential for developing microsystems and devices for a wide range of applications.Despite their considerable poten-tial,existing techniques are mainly used in laboratory research settings.This review provides an over-view of the fundamentals,techniques,and applications of microassemblies.Manipulation techniques based on magnetic,optical,acoustic fields,and mechanical systems are discussed,and control systems that rely on machine vision and force feedback are introduced.Additionally,recent applications of microassemblies in microstructure fabrication,microelectromechanical operation,and biomedical engi-neering are examined.This review also highlights unmet technical demands and emerging trends,as well as new research opportunities in this expanding field of research driven by allied technologies such as microrobotics.展开更多
Computational analysis of electrostatic microelectromechanical systems （MEMS） requires an electrostatic analysis to compute the electrostatic forces acting on micromechanical structures and a mechanical analysis to ...Computational analysis of electrostatic microelectromechanical systems （MEMS） requires an electrostatic analysis to compute the electrostatic forces acting on micromechanical structures and a mechanical analysis to compute the deformation of micromechanical structures. Typically, the mechanical analysis is performed on an undeformed geometry. However, the electrostatic analysis is performed on the deformed position of microstructures. In this paper, a new efficient approach to self-consistent analysis of electrostatic MEMS in the small deformation case is presented. In this approach, when the microstructures undergo small deformations, the surface charge densities on the deformed geometry can be computed without updating the geometry of the microstructures. This algorithm is based on the linear mode shapes of a microstructure as basis functions. A boundary integral equation for the electrostatic problem is expanded into a Taylor series around the undeformed configuration, and a new coupled-field equation is presented. This approach is validated by comparing its results with the results available in the literature and ANSYS solutions, and shows attractive features comparable to ANSYS.展开更多
A solenoid-type inductor for high frequency application is realized using a micro-electro-mechanical systems (MEMS) technique.In order to achieve a high inductance value and Q-factor,UV-LIGA,dry etching technique,fine...A solenoid-type inductor for high frequency application is realized using a micro-electro-mechanical systems (MEMS) technique.In order to achieve a high inductance value and Q-factor,UV-LIGA,dry etching technique,fine polishing and electroplating technique are adopted.The dimensions of the inductor are 1500μm×900μm×70μm,having 41 turns with a coil width of 20μm separated by 20μm spaces and a high aspect ratio of 3.5∶1.The maximum measured inductance of the inductor is 6.17nH with a Q-factor of about 6.展开更多
Microreaction technology is one of the most innovative and rapid developing fields in chemical engineering, synthesis and process technology. Many expectations toward enhanced product selectivity, yield and purity, im...Microreaction technology is one of the most innovative and rapid developing fields in chemical engineering, synthesis and process technology. Many expectations toward enhanced product selectivity, yield and purity, improved safety, and access to new products and processes are directed to the microreaction technology. Microfluidic mixer is the most important component in microfluidic devices. Based on various principles, active and passive micromixers have been designed and investigated. This review is focused on the recent developments in microfluidic mixers. An overview of the flow phenomena and mixing characteristics in active and passive micromixers is presented, including the types of physical phenomena and their utilization in micromixers. Due to the simple fabrication technology and the easy implementation in a complex microfluidic system, T-micromixer is highlighted as an example to illustrate the effect of design and operating parameters on mixing efficiency and fuid flow inside microfluidic mixers.展开更多
This paper investigates the effects of material and dimension parameters on the frequency splitting,frequency drift,and quality factor(Q)of aluminium nitride(AlN)-on-n-doped/pure silicon(Si)microelectromechanical syst...This paper investigates the effects of material and dimension parameters on the frequency splitting,frequency drift,and quality factor(Q)of aluminium nitride(AlN)-on-n-doped/pure silicon(Si)microelectromechanical systems(MEMS)disk resonators through analysis and simulation.These parameters include the crystallographic orientation,dopant,substrate thickness,and temperature.The resonators operate in the elliptical,higher order,and flexural modes.The simulation results show that i)the turnover points of the resonators exist at 55°C,-50°C,40°C,and-10°C for n-doped silicon with the doping concentration of 2×1019 cm-3 and the Si thickness of 3.5μm,and these points are shifted with the substrate thickness and mode variations;ii)compared with pure Si,the modal-frequency splitting for n-doped Si is higher and increases from 5%to 10%for all studied modes;iii)Q of the resonators depends on the temperature and dopant.Therefore,the turnover,modal-frequency splitting,and Q of the resonators depend on the thickness and material of the substrate and the temperature.This work offers an analysis and design platform for high-performance MEMS gyroscopes as well as oscillators in terms of the temperature compensation by n-doped Si.展开更多
Thin film is a widely used structure in the present microelectromechanical systems (MEMS) and plays a vital role in many functional devices. However, the great size difference between the film's thickness and its ...Thin film is a widely used structure in the present microelectromechanical systems (MEMS) and plays a vital role in many functional devices. However, the great size difference between the film's thickness and its planar dimensions makes it difficult to study the thin film performance numerically. In this work, a scaling transformation was presented to make the different dimensional sizes equivalent, and thereby, to improve the grid quality considerably. Two numerical experiments were studied to validate the present scaling transformation method. The numerical results indicated that the largest grid size difference can be decreased to one to two orders of magnitude by using the present scaling transformation, and the memory required by the numerical simulation, i.e., the total grid number, could be reduced by about two to three orders of magnitude, while the numerical accuracies with and without this scaling transformation were nearly the same.展开更多
A new analytical model of a 3-degree-of-freedom （3-DOF） gyro-accelerometer system consisting of a 1-DOF drive and 2-DOF sense modes is presented. The model constructs lumped differential equations associated with ea...A new analytical model of a 3-degree-of-freedom （3-DOF） gyro-accelerometer system consisting of a 1-DOF drive and 2-DOF sense modes is presented. The model constructs lumped differential equations associated with each DOFof the system by vector analysis. The coupled differential equations thus established are solved analytically for their responses in both the time and frequency domains. Considering these frequency response equations, novel device design concepts are derived by forcing the sense phase to zero, which leads to a certain relationship between the structural frequencies, thereby causing minimization of the damping effect on the performance of the system. Furthermore, the feasibility of the present gyro-accelerometer structure is studied using a unique discriminatory scheme for the detection of both gyro action and linear acceleration at their events. This scheme combines the formulated settled transient solution of the gyro-accelerometer with the processes of synchronous demodulation and filtration, which leads to the in-phase and quadrature components of the system＇s output signal. These two components can be utilized in the detection of angular motion and linear acceleration. The obtained analytical results are validated by simulation in a MATLAB/Simulink environment, and it is found that the results are in excellent agreement with each other.展开更多
Based on MEMS technology,immunosensor with an'Au,Pt,Pt'three-microelectrode system enclosed in a SU-8 micro pool was fabricated.Employing SAMs technique,the Au electrode was modified by cysteamine(Cys)to assem...Based on MEMS technology,immunosensor with an'Au,Pt,Pt'three-microelectrode system enclosed in a SU-8 micro pool was fabricated.Employing SAMs technique,the Au electrode was modified by cysteamine(Cys)to assemble gold nanopanicles(nanogold)layer,subsequently,a layer of protein G(PG)was immobilized on nanogold layer to further capture antibody orientedly.Compared with the immunosensors using bulky gold electrode and direct PG binding to electrode immobilization technique for antibody,it has attractive advantages,such as miniaturization,good compatibility,broad linear range for human immunoglobulin(HIgG)and easy to be designed into array.展开更多
This paper is focused on electrode design for piezoelectric tuning fork resonators.The relationship between the performance and electrode pattern of aluminum nitride piezoelectric tuning fork resonators vibrating in t...This paper is focused on electrode design for piezoelectric tuning fork resonators.The relationship between the performance and electrode pattern of aluminum nitride piezoelectric tuning fork resonators vibrating in the in-plane flexural mode is investigated based on a set of resonators with different electrode lengths,widths,and ratios.Experimental and simulation results show that the electrode design impacts greatly the multimode effect induced from torsional modes but has little influence on other loss mechanisms.Optimizing the electrode design suppresses the torsional mode successfully,thereby increasing the ratio of impedance at parallel and series resonant frequencies(R_(p)/R_(s))by more than 80%and achieving a quality factor(Q)of 7753,an effective electromechanical coupling coefficient(kt_(eff)^(2))of 0.066%,and an impedance at series resonant frequency(R_(m))of 23.6 kΩ.The proposed approach shows great potential for high-performance piezoelectric resonators,which are likely to be fundamental building blocks for sensors with high sensitivity and low noise and power consumption.展开更多
Modeling vapor pressure is crucial for studying the moisture reliability of microelectronics, as high vapor pressure can cause device failures in environments with high temperature and humidity. To minimize the impact...Modeling vapor pressure is crucial for studying the moisture reliability of microelectronics, as high vapor pressure can cause device failures in environments with high temperature and humidity. To minimize the impact of vapor pressure, a super-hydrophobic(SH) coating can be applied on the exterior surface of devices in order to prevent moisture penetration. The underlying mechanism of SH coating for enhancing device reliability, however, is still not fully understood. In this paper, we present several existing theories for predicting vapor pressure within microelectronic materials. In addition, we discuss the mechanism and effectiveness of SH coating in preventing water vapor from entering a device, based on experimental results. Two theoretical models, a micro-mechanics-based whole-field vapor pressure model and a convection-diffusion model, are described for predicting vapor pressure. Both methods have been successfully used to explain experimental results on uncoated samples. However, when a device was coated with an SH nanocomposite, weight gain was still observed, likely due to vapor penetration through the SH surface. This phenomenon may cast doubt on the effectiveness of SH coatings in microelectronic devices. Based on current theories and the available experimental results, we conclude that it is necessary to develop a new theory to understand how water vapor penetrates through SH coatings and impacts the materials underneath. Such a theory could greatly improve microelectronics reliability.展开更多
This paper discusses fabrication and performance of novel circular spiral inductors on silicon. The substrate materials underneath the inductor coil are removed by wet etching process. In the fabrication process, fine...This paper discusses fabrication and performance of novel circular spiral inductors on silicon. The substrate materials underneath the inductor coil are removed by wet etching process. In the fabrication process, fine polishing of the photoresist is used to simplify the processes and ensure perfect contact between the seed layer and the top of pillars. Dry etching technique is used to remove the seed layer. The results show that Q-factor of the inductor is greatly improved by removing silicon underneath the inductor coil. The spiral inductor with line width of 50 μm has a peak Q-factor of 10 for the inductance of 2.5 nH at frequency of 1 GHz, and the resonance frequency of the inductor is about 8.5 GHz. For the inductor of conductor width 80 μm, the peak Q-factor increases to about 17 for inductance of 1.5 nH in the frequency range of 0.05 -3.00 GHz.展开更多
This paper presents a reduced-order model to describe the mechanical behaviour of microbeam-based magnetic devices. The integration for magnetic force is calculated by dividing the microbeam into several segments, and...This paper presents a reduced-order model to describe the mechanical behaviour of microbeam-based magnetic devices. The integration for magnetic force is calculated by dividing the microbeam into several segments, and the nonlinear equation set has been developed based on the magnetic circuit principle. In comparison with previous models, the present macromodel accounts for both the micro-magnetic-core reluctance and the coupling between the beam deflection and magnetic force. This macromodel is validated by comparing with the experimental results available in some papers and finite-element solutions.展开更多
Polysilicon Microelectromechanical systems(MEMS) are the subject of intensive researches. Surface chemistry and topography of a MEMS test structure fabricated at Sandia National Laboratory, USA, were studied by means ...Polysilicon Microelectromechanical systems(MEMS) are the subject of intensive researches. Surface chemistry and topography of a MEMS test structure fabricated at Sandia National Laboratory, USA, were studied by means of scanning electron microscopy(SEM), X-ray photoelectron spectroscopy(XPS) and atomic force microscopy(AFM). XPS C_ 1sand Si_ 2pspectra from the polysilicon components, silicon nitride substrate and a reference silicon wafer were compared. The results confirm the presence of a self-assembled monolayer(SAM) on the MEMS surface. An island-like morphology was found on both polysilicon and silicon nitride surfaces of the MEMS. The islands take the form of caps, being up to 0.5 μm in diameter and 20 nm in height. It is concluded that the co-existence of columnar growth and equiaxed growth during the low pressure chemical vapor deposition(LPCVD) of these layers leads to the observed morphology and the islands are caps to the columnar structures.展开更多
A 4.13 MHz reference oscillator incorporating a capacitive single-crystal-silicon （SCS） micromechanical resonator is presented. The microresonator is fabricated using a cavity silicon-on-insulator （cavity-SOl） pro...A 4.13 MHz reference oscillator incorporating a capacitive single-crystal-silicon （SCS） micromechanical resonator is presented. The microresonator is fabricated using a cavity silicon-on-insulator （cavity-SOl） process and is excited in the Lain6 mode with electrostatic driving and capacitive sensing. The Lam6 mode may be described as a square plate that is cont- racting along one axis in the fabrication plane, while simultaneously extending along an orthogonal axis in the same plane. The microresonator exhibits a quality factor as high as 1.4 × 10^6 and a resonant frequency of 4.13 MHz at a pressure of 0.08 mbar. The output spectrum of the oscillator shows that the silicon micromechanical resonator is adapted as a timing element for a precision oscillator.展开更多
A novel MEMS device boning system is presented. Aiming at the high velocity, high precision and high flexibility requirements, a novel manipulator of planar parallel structure is developed to substitute ordinary X-Y t...A novel MEMS device boning system is presented. Aiming at the high velocity, high precision and high flexibility requirements, a novel manipulator of planar parallel structure is developed to substitute ordinary X-Y table. In addition, the machine vision is implemented to improve the system＇ s flexibility. The initial angular positions of the joints are estimated by the extended Kalman filter algorithm. As a resuh, the manipulator＇s absolute locating accuracy in its workspace is guaranteed indirectly. For any MEMS device, the bonding system itself can be used as measurement equipment to create the device＇ s geometry model, which is the base to do off-line programming. A quite ideal trade-off between the system＇ s flexibility and efficiency is got. Finally, some verified motion specification of the manipulator, the bonding experimental results and the verified qualities of the bonded devices are provided.展开更多
The design and optimization of two types of novel miniature vibrating Electric Field Sensors (EFSs) based on Micro Electro Mechanical Systems (MEMS) technology are presented.They have different structures and vibratin...The design and optimization of two types of novel miniature vibrating Electric Field Sensors (EFSs) based on Micro Electro Mechanical Systems (MEMS) technology are presented.They have different structures and vibrating modes. The volume is much smaller than other types of charge-induced EFSs such as field-mills. As miniaturizing, the induced signal is reduced enormously and a high sensitive circuit is needed to detect it. Elaborately designed electrodes can increase the amplitude of the output current, making the detecting circuit simplified and improving the signal-to-noise ratio. Computer simulations for different structural parameters of the EFSs and vibrating methods have been carried out by Finite Element Method (FEM). It is proved that the new structures are realizable and the output signals are detectable.展开更多
This paper describes a novel,system-level design methodology based on a genetic algorithm(GA)using freeform geometries for microelectromechanical systems(MEMS)devices.The proposed method can concurrently design and co...This paper describes a novel,system-level design methodology based on a genetic algorithm(GA)using freeform geometries for microelectromechanical systems(MEMS)devices.The proposed method can concurrently design and co-optimize the electronic and mechanical parts of a MEMS device comprising freeform geometries to achieve a better system performance,i.e.,a high sensitivity,a good system stability,and large fabrication tolerances.Also,the introduction of freeform geometries allows higher degrees of freedom in the design process,improving the diversity and potentially the performance of the MEMS devices.A MEMS accelerometer comprising a freeform mechanical motion preamplifier in a closed-loop control system is presented to demonstrate the effectiveness of the design approach.The optimization process shows the main figure-of-merit(FOM)is improved by 195%.In the mechanical component alone(open-loop system),the product of sensitivity and bandwidth has improved by 151%,with sensitivity increasing by 276%.For closed-loop performance,there is an improvement of 120%for the ratio of open and closed-loop displacements.The product of sensitivity and bandwidth is improved by 27%in the closed-loop system.Excellent immunities to fabrication errors and parameter mismatch are achieved.Experiments show that the displacement of the MEMS accelerometer in the closed-loop system decreased by 86%with 4.85 V feedback voltage compared with that in the open-loop system under a 1 g 100 Hz acceleration input.The static and dynamic nonlinearities in the closed-loop system are improved by 64%and 61%,respectively,compared with those in the open-loop system,in the±1 g acceleration input range.Besides,the closed-loop system improves the cross-axis sensitivity by 18.43%,compared with that in the open-loop system.It is the first time a closed-loop system for a MEMS accelerometer comprising a mechanical motion preamplifier is successfully implemented experimentally.展开更多
Microelectromechanical systems(MEMS)gyroscopes with higher precision have always been a focal point of research.Due to limitations in resonant structure,fabrication processes,and measurement and control techniques,MEM...Microelectromechanical systems(MEMS)gyroscopes with higher precision have always been a focal point of research.Due to limitations in resonant structure,fabrication processes,and measurement and control techniques,MEMS gyroscopes with bias instability better than 0.01°/h are still rare and expensive.This paper incorporates electrode machining error and capacitance detection nonlinear error into the gyroscope model,resulting in a more comprehensive bias output model.Based on this,a mode reversal combined mode deflection control method is proposed to eliminate the thermal drift and decrease the bias instability of the gyroscope.Experimental results demonstrate that compared with the traditional force-to-rebalance mode,the new method achieves a 595 times reduction in bias variation during−40℃ to+60℃ temperature cycles and a 6.3 times reduction in bias instability at room temperature.The average bias instability of honeycomb disk resonator gyroscopes can reach 0.003°/h at integration times of 8500 s after applying the new method across three prototypes,which is the best reported performance of the MEMS gyroscope thus far.This paper provides a new paradigm for achieving higher precision MEMS gyroscopes.展开更多
In this article,a two-dimensional(2D)honeycomb lattice phononic crystal(PnC)based micro-oven with large bandgap is introduced to be integrated with piezoelectric microelectromechanical systems(MEMS)resonator to reduce...In this article,a two-dimensional(2D)honeycomb lattice phononic crystal(PnC)based micro-oven with large bandgap is introduced to be integrated with piezoelectric microelectromechanical systems(MEMS)resonator to reduce anchor loss for timing applications.Finite element method(FEM)analysis and experimental measurement were performed to verify that the proposed PnC microoven design gives advantage in quality factor(Q).The measurement results demonstrate that the resonator with 2D honeycomb lattice PnC micro-oven shows a repeatable 1.7 times improvement of average Q compared with the bare one.The resonator with micro-oven control was further measured for frequency stability.The proposed piezoelectric micro-oven-controlled MEMS resonator achieves a frequency stability of less than±10 ppb in a stable environment,which indicates promising potential for application in high-end timingfield.展开更多
Adhesive and corrosive wear at microscales are quantitatively distinguished in lifetime tests of resonant bulk-fabricated silicon microelectromechanical systems(MEMS).By analyzing the oscillation decay characteristics...Adhesive and corrosive wear at microscales are quantitatively distinguished in lifetime tests of resonant bulk-fabricated silicon microelectromechanical systems(MEMS).By analyzing the oscillation decay characteristics in different vapor environments,we find that wear is dominated by asperity adhesion during the initial stages of rubbing in dry N2 or O2/N2 mixtures;in these situations the transient wear rate is inversely proportional to the wear depth.But in water or ethanol vapors,chemical reactions between the corrosive adsorbed layer and the silicon substrate limit the wear rate to a constant.These observations are consistent with atomic explanations.The differences between adhesive and corrosive wear explain the advantages offered by lubricating with alcohol vapors rather than using dry environments for tribo-MEMS devices.Compared to ethanol,the relatively poor anti-wear effect of water vapor is explained by aggressive and rapid tribo-reactions.展开更多
基金supported by Shanghai Municipal Science and Technology Major Project(2021SHZDZX)also in part supported by the Science and Technology Commission of Shanghai Municipality(20DZ2220400).
文摘Microassembly platforms have attracted significant attention recently because of their potential for developing microsystems and devices for a wide range of applications.Despite their considerable poten-tial,existing techniques are mainly used in laboratory research settings.This review provides an over-view of the fundamentals,techniques,and applications of microassemblies.Manipulation techniques based on magnetic,optical,acoustic fields,and mechanical systems are discussed,and control systems that rely on machine vision and force feedback are introduced.Additionally,recent applications of microassemblies in microstructure fabrication,microelectromechanical operation,and biomedical engi-neering are examined.This review also highlights unmet technical demands and emerging trends,as well as new research opportunities in this expanding field of research driven by allied technologies such as microrobotics.
基金Project supported by the National Natural Science Foundation of China (Grant No 50675034)the Natural Science Foundation of Jiangsu Province of China (Grant No SBK200920386)
文摘Computational analysis of electrostatic microelectromechanical systems （MEMS） requires an electrostatic analysis to compute the electrostatic forces acting on micromechanical structures and a mechanical analysis to compute the deformation of micromechanical structures. Typically, the mechanical analysis is performed on an undeformed geometry. However, the electrostatic analysis is performed on the deformed position of microstructures. In this paper, a new efficient approach to self-consistent analysis of electrostatic MEMS in the small deformation case is presented. In this approach, when the microstructures undergo small deformations, the surface charge densities on the deformed geometry can be computed without updating the geometry of the microstructures. This algorithm is based on the linear mode shapes of a microstructure as basis functions. A boundary integral equation for the electrostatic problem is expanded into a Taylor series around the undeformed configuration, and a new coupled-field equation is presented. This approach is validated by comparing its results with the results available in the literature and ANSYS solutions, and shows attractive features comparable to ANSYS.
文摘A solenoid-type inductor for high frequency application is realized using a micro-electro-mechanical systems (MEMS) technique.In order to achieve a high inductance value and Q-factor,UV-LIGA,dry etching technique,fine polishing and electroplating technique are adopted.The dimensions of the inductor are 1500μm×900μm×70μm,having 41 turns with a coil width of 20μm separated by 20μm spaces and a high aspect ratio of 3.5∶1.The maximum measured inductance of the inductor is 6.17nH with a Q-factor of about 6.
基金the National High Technology Research and Development Program of China(2006AA030202,2006AA05Z316)
文摘Microreaction technology is one of the most innovative and rapid developing fields in chemical engineering, synthesis and process technology. Many expectations toward enhanced product selectivity, yield and purity, improved safety, and access to new products and processes are directed to the microreaction technology. Microfluidic mixer is the most important component in microfluidic devices. Based on various principles, active and passive micromixers have been designed and investigated. This review is focused on the recent developments in microfluidic mixers. An overview of the flow phenomena and mixing characteristics in active and passive micromixers is presented, including the types of physical phenomena and their utilization in micromixers. Due to the simple fabrication technology and the easy implementation in a complex microfluidic system, T-micromixer is highlighted as an example to illustrate the effect of design and operating parameters on mixing efficiency and fuid flow inside microfluidic mixers.
文摘This paper investigates the effects of material and dimension parameters on the frequency splitting,frequency drift,and quality factor(Q)of aluminium nitride(AlN)-on-n-doped/pure silicon(Si)microelectromechanical systems(MEMS)disk resonators through analysis and simulation.These parameters include the crystallographic orientation,dopant,substrate thickness,and temperature.The resonators operate in the elliptical,higher order,and flexural modes.The simulation results show that i)the turnover points of the resonators exist at 55°C,-50°C,40°C,and-10°C for n-doped silicon with the doping concentration of 2×1019 cm-3 and the Si thickness of 3.5μm,and these points are shifted with the substrate thickness and mode variations;ii)compared with pure Si,the modal-frequency splitting for n-doped Si is higher and increases from 5%to 10%for all studied modes;iii)Q of the resonators depends on the temperature and dopant.Therefore,the turnover,modal-frequency splitting,and Q of the resonators depend on the thickness and material of the substrate and the temperature.This work offers an analysis and design platform for high-performance MEMS gyroscopes as well as oscillators in terms of the temperature compensation by n-doped Si.
基金National Natural Science Foundation of China(No.60576020,No.60606014).
文摘Thin film is a widely used structure in the present microelectromechanical systems (MEMS) and plays a vital role in many functional devices. However, the great size difference between the film's thickness and its planar dimensions makes it difficult to study the thin film performance numerically. In this work, a scaling transformation was presented to make the different dimensional sizes equivalent, and thereby, to improve the grid quality considerably. Two numerical experiments were studied to validate the present scaling transformation method. The numerical results indicated that the largest grid size difference can be decreased to one to two orders of magnitude by using the present scaling transformation, and the memory required by the numerical simulation, i.e., the total grid number, could be reduced by about two to three orders of magnitude, while the numerical accuracies with and without this scaling transformation were nearly the same.
文摘A new analytical model of a 3-degree-of-freedom （3-DOF） gyro-accelerometer system consisting of a 1-DOF drive and 2-DOF sense modes is presented. The model constructs lumped differential equations associated with each DOFof the system by vector analysis. The coupled differential equations thus established are solved analytically for their responses in both the time and frequency domains. Considering these frequency response equations, novel device design concepts are derived by forcing the sense phase to zero, which leads to a certain relationship between the structural frequencies, thereby causing minimization of the damping effect on the performance of the system. Furthermore, the feasibility of the present gyro-accelerometer structure is studied using a unique discriminatory scheme for the detection of both gyro action and linear acceleration at their events. This scheme combines the formulated settled transient solution of the gyro-accelerometer with the processes of synchronous demodulation and filtration, which leads to the in-phase and quadrature components of the system＇s output signal. These two components can be utilized in the detection of angular motion and linear acceleration. The obtained analytical results are validated by simulation in a MATLAB/Simulink environment, and it is found that the results are in excellent agreement with each other.
基金This work is supported by the National Natural Science Foundation of China （Grant No. 90307014）.
文摘Based on MEMS technology,immunosensor with an'Au,Pt,Pt'three-microelectrode system enclosed in a SU-8 micro pool was fabricated.Employing SAMs technique,the Au electrode was modified by cysteamine(Cys)to assemble gold nanopanicles(nanogold)layer,subsequently,a layer of protein G(PG)was immobilized on nanogold layer to further capture antibody orientedly.Compared with the immunosensors using bulky gold electrode and direct PG binding to electrode immobilization technique for antibody,it has attractive advantages,such as miniaturization,good compatibility,broad linear range for human immunoglobulin(HIgG)and easy to be designed into array.
基金supported in part by the National Key Research and Development Program of China (Grant No.2020YFB2008800)the Nanchang Institute for Microtechnology of Tianjin University。
文摘This paper is focused on electrode design for piezoelectric tuning fork resonators.The relationship between the performance and electrode pattern of aluminum nitride piezoelectric tuning fork resonators vibrating in the in-plane flexural mode is investigated based on a set of resonators with different electrode lengths,widths,and ratios.Experimental and simulation results show that the electrode design impacts greatly the multimode effect induced from torsional modes but has little influence on other loss mechanisms.Optimizing the electrode design suppresses the torsional mode successfully,thereby increasing the ratio of impedance at parallel and series resonant frequencies(R_(p)/R_(s))by more than 80%and achieving a quality factor(Q)of 7753,an effective electromechanical coupling coefficient(kt_(eff)^(2))of 0.066%,and an impedance at series resonant frequency(R_(m))of 23.6 kΩ.The proposed approach shows great potential for high-performance piezoelectric resonators,which are likely to be fundamental building blocks for sensors with high sensitivity and low noise and power consumption.
基金the support of the National High-Tech Research and Development Program of China (863 Program) (2015AA03A101)
文摘Modeling vapor pressure is crucial for studying the moisture reliability of microelectronics, as high vapor pressure can cause device failures in environments with high temperature and humidity. To minimize the impact of vapor pressure, a super-hydrophobic(SH) coating can be applied on the exterior surface of devices in order to prevent moisture penetration. The underlying mechanism of SH coating for enhancing device reliability, however, is still not fully understood. In this paper, we present several existing theories for predicting vapor pressure within microelectronic materials. In addition, we discuss the mechanism and effectiveness of SH coating in preventing water vapor from entering a device, based on experimental results. Two theoretical models, a micro-mechanics-based whole-field vapor pressure model and a convection-diffusion model, are described for predicting vapor pressure. Both methods have been successfully used to explain experimental results on uncoated samples. However, when a device was coated with an SH nanocomposite, weight gain was still observed, likely due to vapor penetration through the SH surface. This phenomenon may cast doubt on the effectiveness of SH coatings in microelectronic devices. Based on current theories and the available experimental results, we conclude that it is necessary to develop a new theory to understand how water vapor penetrates through SH coatings and impacts the materials underneath. Such a theory could greatly improve microelectronics reliability.
文摘This paper discusses fabrication and performance of novel circular spiral inductors on silicon. The substrate materials underneath the inductor coil are removed by wet etching process. In the fabrication process, fine polishing of the photoresist is used to simplify the processes and ensure perfect contact between the seed layer and the top of pillars. Dry etching technique is used to remove the seed layer. The results show that Q-factor of the inductor is greatly improved by removing silicon underneath the inductor coil. The spiral inductor with line width of 50 μm has a peak Q-factor of 10 for the inductance of 2.5 nH at frequency of 1 GHz, and the resonance frequency of the inductor is about 8.5 GHz. For the inductor of conductor width 80 μm, the peak Q-factor increases to about 17 for inductance of 1.5 nH in the frequency range of 0.05 -3.00 GHz.
基金supported in part by the National High Technology Research and Development Program of China (Grant No2006AA04z302)
文摘This paper presents a reduced-order model to describe the mechanical behaviour of microbeam-based magnetic devices. The integration for magnetic force is calculated by dividing the microbeam into several segments, and the nonlinear equation set has been developed based on the magnetic circuit principle. In comparison with previous models, the present macromodel accounts for both the micro-magnetic-core reluctance and the coupling between the beam deflection and magnetic force. This macromodel is validated by comparing with the experimental results available in some papers and finite-element solutions.
文摘Polysilicon Microelectromechanical systems(MEMS) are the subject of intensive researches. Surface chemistry and topography of a MEMS test structure fabricated at Sandia National Laboratory, USA, were studied by means of scanning electron microscopy(SEM), X-ray photoelectron spectroscopy(XPS) and atomic force microscopy(AFM). XPS C_ 1sand Si_ 2pspectra from the polysilicon components, silicon nitride substrate and a reference silicon wafer were compared. The results confirm the presence of a self-assembled monolayer(SAM) on the MEMS surface. An island-like morphology was found on both polysilicon and silicon nitride surfaces of the MEMS. The islands take the form of caps, being up to 0.5 μm in diameter and 20 nm in height. It is concluded that the co-existence of columnar growth and equiaxed growth during the low pressure chemical vapor deposition(LPCVD) of these layers leads to the observed morphology and the islands are caps to the columnar structures.
文摘A 4.13 MHz reference oscillator incorporating a capacitive single-crystal-silicon （SCS） micromechanical resonator is presented. The microresonator is fabricated using a cavity silicon-on-insulator （cavity-SOl） process and is excited in the Lain6 mode with electrostatic driving and capacitive sensing. The Lam6 mode may be described as a square plate that is cont- racting along one axis in the fabrication plane, while simultaneously extending along an orthogonal axis in the same plane. The microresonator exhibits a quality factor as high as 1.4 × 10^6 and a resonant frequency of 4.13 MHz at a pressure of 0.08 mbar. The output spectrum of the oscillator shows that the silicon micromechanical resonator is adapted as a timing element for a precision oscillator.
基金Supported by the High Technology Research and Development Programme of China （No. 2003AA404060） and the National Natural Science Foundation of China （No.60405008）.
文摘A novel MEMS device boning system is presented. Aiming at the high velocity, high precision and high flexibility requirements, a novel manipulator of planar parallel structure is developed to substitute ordinary X-Y table. In addition, the machine vision is implemented to improve the system＇ s flexibility. The initial angular positions of the joints are estimated by the extended Kalman filter algorithm. As a resuh, the manipulator＇s absolute locating accuracy in its workspace is guaranteed indirectly. For any MEMS device, the bonding system itself can be used as measurement equipment to create the device＇ s geometry model, which is the base to do off-line programming. A quite ideal trade-off between the system＇ s flexibility and efficiency is got. Finally, some verified motion specification of the manipulator, the bonding experimental results and the verified qualities of the bonded devices are provided.
基金Supported by the National Natural Science Foundation of China (No.60172001).
文摘The design and optimization of two types of novel miniature vibrating Electric Field Sensors (EFSs) based on Micro Electro Mechanical Systems (MEMS) technology are presented.They have different structures and vibrating modes. The volume is much smaller than other types of charge-induced EFSs such as field-mills. As miniaturizing, the induced signal is reduced enormously and a high sensitive circuit is needed to detect it. Elaborately designed electrodes can increase the amplitude of the output current, making the detecting circuit simplified and improving the signal-to-noise ratio. Computer simulations for different structural parameters of the EFSs and vibrating methods have been carried out by Finite Element Method (FEM). It is proved that the new structures are realizable and the output signals are detectable.
基金supported by The Science and Technology Development Fund,Macao SAR(FDCT),004/2023/SKLThe Science and Technology Development Fund,Macao SAR(FDCT),0087/2023/ITP2.
文摘This paper describes a novel,system-level design methodology based on a genetic algorithm(GA)using freeform geometries for microelectromechanical systems(MEMS)devices.The proposed method can concurrently design and co-optimize the electronic and mechanical parts of a MEMS device comprising freeform geometries to achieve a better system performance,i.e.,a high sensitivity,a good system stability,and large fabrication tolerances.Also,the introduction of freeform geometries allows higher degrees of freedom in the design process,improving the diversity and potentially the performance of the MEMS devices.A MEMS accelerometer comprising a freeform mechanical motion preamplifier in a closed-loop control system is presented to demonstrate the effectiveness of the design approach.The optimization process shows the main figure-of-merit(FOM)is improved by 195%.In the mechanical component alone(open-loop system),the product of sensitivity and bandwidth has improved by 151%,with sensitivity increasing by 276%.For closed-loop performance,there is an improvement of 120%for the ratio of open and closed-loop displacements.The product of sensitivity and bandwidth is improved by 27%in the closed-loop system.Excellent immunities to fabrication errors and parameter mismatch are achieved.Experiments show that the displacement of the MEMS accelerometer in the closed-loop system decreased by 86%with 4.85 V feedback voltage compared with that in the open-loop system under a 1 g 100 Hz acceleration input.The static and dynamic nonlinearities in the closed-loop system are improved by 64%and 61%,respectively,compared with those in the open-loop system,in the±1 g acceleration input range.Besides,the closed-loop system improves the cross-axis sensitivity by 18.43%,compared with that in the open-loop system.It is the first time a closed-loop system for a MEMS accelerometer comprising a mechanical motion preamplifier is successfully implemented experimentally.
基金supported by the National Key Research and Development Program of China under grant no.2022YFB3207301in part by the National Natural Science Foundation of China under grant 62304255 and grant U21A20505。
文摘Microelectromechanical systems(MEMS)gyroscopes with higher precision have always been a focal point of research.Due to limitations in resonant structure,fabrication processes,and measurement and control techniques,MEMS gyroscopes with bias instability better than 0.01°/h are still rare and expensive.This paper incorporates electrode machining error and capacitance detection nonlinear error into the gyroscope model,resulting in a more comprehensive bias output model.Based on this,a mode reversal combined mode deflection control method is proposed to eliminate the thermal drift and decrease the bias instability of the gyroscope.Experimental results demonstrate that compared with the traditional force-to-rebalance mode,the new method achieves a 595 times reduction in bias variation during−40℃ to+60℃ temperature cycles and a 6.3 times reduction in bias instability at room temperature.The average bias instability of honeycomb disk resonator gyroscopes can reach 0.003°/h at integration times of 8500 s after applying the new method across three prototypes,which is the best reported performance of the MEMS gyroscope thus far.This paper provides a new paradigm for achieving higher precision MEMS gyroscopes.
文摘In this article,a two-dimensional(2D)honeycomb lattice phononic crystal(PnC)based micro-oven with large bandgap is introduced to be integrated with piezoelectric microelectromechanical systems(MEMS)resonator to reduce anchor loss for timing applications.Finite element method(FEM)analysis and experimental measurement were performed to verify that the proposed PnC microoven design gives advantage in quality factor(Q).The measurement results demonstrate that the resonator with 2D honeycomb lattice PnC micro-oven shows a repeatable 1.7 times improvement of average Q compared with the bare one.The resonator with micro-oven control was further measured for frequency stability.The proposed piezoelectric micro-oven-controlled MEMS resonator achieves a frequency stability of less than±10 ppb in a stable environment,which indicates promising potential for application in high-end timingfield.
基金the National Natural Science Foundation of China(NSFC,Nos.91123033 and 51021064).
文摘Adhesive and corrosive wear at microscales are quantitatively distinguished in lifetime tests of resonant bulk-fabricated silicon microelectromechanical systems(MEMS).By analyzing the oscillation decay characteristics in different vapor environments,we find that wear is dominated by asperity adhesion during the initial stages of rubbing in dry N2 or O2/N2 mixtures;in these situations the transient wear rate is inversely proportional to the wear depth.But in water or ethanol vapors,chemical reactions between the corrosive adsorbed layer and the silicon substrate limit the wear rate to a constant.These observations are consistent with atomic explanations.The differences between adhesive and corrosive wear explain the advantages offered by lubricating with alcohol vapors rather than using dry environments for tribo-MEMS devices.Compared to ethanol,the relatively poor anti-wear effect of water vapor is explained by aggressive and rapid tribo-reactions.
