An eight-channel variable optical attenuator (VOA) array fabricated by MEMS technology is presented. Based on micro electromagnetic actuation, the attenuation level is adjusted by changing the radial offset between the input/output optical fiber. The relationship between the attenuation and the offset was analyzed based on wave-guide transmission theory. The structure parameter was determined through mechanics and magnetic circuit analysis. The device was fabricated and packaged by micromachining technology. The packaged volume of the device is 80×40×12mm³. According to the experiment results, the insertion loss is less than 1dB, the polarization dependent loss is less than 0.1dB, dynamic range is above 35dB and the driving voltage is less than 5V. It is proved to be a low cost, high performance passive device for future all-optical-networks.

High reflectivity Distributed Bragg Reflector (DBR) mirrors comprising of quarter wavelength stacks of epitaxial or dielectric layers are essential in various photonic active and passive devices. Our focus has been on optimizing plasma enhanced chemical vapor deposited (PECVD) Si₃N₄/SiO₂ (170nm/255nm ± 20nm) based DBR stacks for high reflectivity to be incorporated in a novel structure comprising of all dielectric based mirrors for tunable resonant cavity devices in a MEMS configuration. Simulated results based on Macleod program predicts a high reflectivity of 99.7% for 10.5 pairs of quarter wavelength layers of Si₃N₄ and SiO₂ centered at the telecom wavelength of 1550 nm. Si₃N₄/SiO₂ DBR pairs of 5.5, 7.5 and 10.5 are deposited by PECVD on InP substrate and reflectance spectra observed on spectrophotometer. A flat pass band of 354nm bandwidth and 99.8% peak reflectivity for 10.5 pairs of DBR stack is observed. Characterization of DBR layers is done using ToF-SIMS for interface abruptness. XPS and Ellispometry is used to ascertain stoichiometry and refractive index respectively. CHF₃ chemistry is used to etch the DBR mirror stacks to achieve highly anisotropic walls by ICP technique, as observed under SEM. We are able to demonstrate filtering of a single wavelength in the C-band region, for different cavity spacing of SiO₂ layer, sandwiched between two highly reflecting mirrors.

A novel Si-based MOEMS acceleration seismic geophone, based on M-Z interferometry, is present in this paper. In one silicon chip, several elements including four silicon beams,seismic mass, a polarizer, M-Z waveguide interferometer and acousto-optic phase modulator are integrated. The working principle and the optimization structure design of the acceleration seismic geophone are given. The simulation result performed in FEM software ANSYS agrees with the theoretical analysis well. The main design parameters of the geophone system is as following: resonance frequency: 1353 Hz; phase detection sensitivity ΔΦ/a: 1.2×10^-4rad/m/s².

The use of micromachined tunable Fabry-Perot interferometers based on compound semiconductors with an integrated photodetector have earlier been proposed [1-3] for fiber optic communications employing Wavelength Division Multiplexing (WDM) for wavelengths around 1.55 μm. The variation of the Fabry-Perot cavity length in these devices is achieved by electrostatic actuation induced movements of a Distributed Bragg Reflector (DBR) mirror suspended by beams. A new filter design has been proposed and its electrostatic actuation induced deflection has been investigated along with three different filter designs using Finite Element Analysis (FEA). Using a mathematical model, deflection is analytically calculated and compared with FEA results. Due to the way in which the mirror is integrated with suspending framework of beams, bending within the mirror during actuation cannot be averted. The filter’s optical performance demands that mirror remain so flat that the maximum bending deflection is 1 nm for the mirror of given dimensions. Using a criterion based on mechanical and optical considerations the length of the beams suspending the mirror has been optimized for each of filter designs under investigation.

Micromachining of optic fiber is one of the key technologies in the field of fiber optic sensing. In this paper, the progress of optic fiber machining has been discussed and our study in this field has been described. Because the main component of fiber optic materials is SiO₂ and the optic fibers are thin, small, hard and crisp, the results of micromachining of optic fiber are poor by using traditional methods. It is impossible to do the partial precise modification for optic fibers or make holes on them and therefore it is difficult to meet the needs of practical use. The newly deep ultraviolet light micromachining technology is the effective technology for the micromachining of optic fiber. By using excimer laser, the three-dimensional micromachining of fiber materials has been studied, and the results show that with the increase of the pulse laser energy, the etching width of the fiber grooves will increase and then keep unchanged after the pulse laser energy reaches a certain value. For the two-dimensional micromachining of fiber materials, it was found that the etching was related to the focused spot quality such as energy uniformity, scanning velocity and repetition frequency, which provides theoretical and technical preliminary for the direct micromachining of optic fiber using excimer laser. Fiber Bragg Grating (FBG) sensors are new sensors which developed in recently years and have important application in many fields. FBG is the key sensing element and can be prepared by the precise micro modification of fiber optic materials. In this paper, the study on the micromachining to change precisely the local refractive ratio of optic fiber materials with excimer laser has performed and FBG can be formed in this way. Various kinds of FBG including single mode, multimode, chirp and long period fiber grating have been prepared, and the FBG sensors for the detection of stress/strain, pressure, temperature, vibration have been manufactured and used in many fields such as bridges, petroleum chemistry, industry and civil construction, navigation.

A theoretical method of focusing X-rays by the compound X-ray refractive lens is presented in this paper. The authors report their resent theoretical results including the material selection and structure parameters for such a device. As an example, a compound X-ray refractive lens with PMMA material is designed. The detailed fabrication process of the PMMA compound lens by LIGA technology is described. Moreover, some measured results by means of SEM are also shown. The structure height of one of the PMMA compound lens is measured to be 500μm.

We fabricated a scanning mirror and optical benches monolithically in a silicon substrate using DRIE process and trench passivation by capillary filling. The micro scanning mirror, actuated by comb electrodes and supported by torsional spring, was fabricated with the optical benches in single crystalline silicon for the integration of optical fibers and ball lenses. Micro prism was adopted for high sensitive fluorescence detection system with scanning mirror. The excitation beam needs to be focused mainly on the slanted area of the micro prism in order to increase optical power efficiency. Considering beam collimation for high power efficiency, beam steering on the micro prism, and simple integration with the micro prism, we proposed silicon scanning mirror having slanted reflective plane and optical benches monolithically fabricated in the same silicon substrate. Reflective surface of the proposed scanning mirror makes parallel incident laser to the substrate be normal downward to the plane of substrate so that optical alignments become simple just by the alignment of scanning mirror’s and micro prism’s substrate. In this research the slanted angle of mirror plane is (-) 54.74 degree inclined instead of 45 degree because the scanning mirror was fabricated in single crystalline silicon (100)-oriented wafer using KOH wet process for the easy fabrication and fast feasibility test. The scanning mirror scans the laser one dimensionally by the actuation so that laser spot can be line-shape on the prism plane. The mirror is a pyramidal structure actuated by comb electrodes and torsion spring. The designed scanning mirror is 2165 x 778 μm² in an upper plane and it has a slanted trapezoidal mirror reflective surface, which size is about 2000 x 1600 μm², considering the micro prism dimension. The maximum deflection angle of the scanning mirror was 7° when 16 V_pp square type voltage is applied to the comb electrodes at resonant frequency.

In this article, a metallographic microscopy, an atomic force microscopy and a field emitting scanning electronic microscopy was used to investigate the surface and the cross-sectional morphology of porous silicon films, respectively. Simple micro-structure and micro-mechanical models are established to explain the origin mechanism of residual stresses in the porous silicon. Experimental results reveal that the residual stresses have close relation with the micro-structure of the porous silicon and consist of the lattice mismatch stress, capillary stress, oxidation stress, Van der Walls force and so on. Combining micro-Raman spectroscopy with x-ray diffraction measurements, we get the total residual stress of 900MPa, and its components of the lattice mismatch stress is about of 815.8MPa, the capillary stress of 13.2MPa and the oxidation stress of 71MPa for a chemical etched porous silicon sample with a certain porosity. It can be seen that the lattice mismatch between the porous layer and the Si substrate is a major source (about 91%) for the total residual stress of the porous silicon.

Graded refractive index Silicon Oxy-nitride thin films were deposited by RF magnetron reactive sputtering at different N₂/O₂ flow ratio. The effects of gas flow ratio on the refractive index, extinction coefficient and composition were studied using UV-VIS spectrophotometer, XPS and FTIR characterization methods. A simple and accurate method is presented for determination of the optical constants and physical thickness of thin films. Which was consisted in fitting the experimental transmission curve with the help of the physical model. The relationship between composition and optical gap and dispersion energy was analyzed using Wemple DiDomenico single-oscillator model. As a result, the samples’ refractive index can be controlled from 1.92 to 1.46 by adjusting the gas flow ratio, and the optical gap lies between 5eV~6.5eV.

Comb-finger structure has been widely used in MEMS device as actuator and capacitive sensing unit. We can quite often find that the capacitance of and electrostatic force between a pair of the fingers are calculated by parallel plate model. This is certainly the simplest and the easiest solution, but with very low accuracy. The analytic method with reasonable accuracy is generally necessary for design engineers because it can give a quick estimation of the design and correct insight into the performance of the design. In this paper, the long comb-finger structure is analyzed. The multi-body-system, e.g., comb-finger above the ground, has been simplified. The fringe field effect is taken into account. Applying semi-empirical equations, we have developed analytic models for calculating capacitance and electrostatic force for various comb-finger structures. The results from the analytic models are compared with simulation results from commercial simulation software.

MEMS Fabry-Perot tunable filter is obviously notable because of its mass production and easy integration. Membrane is the key portion of the filter as its structure directly affects the filter’s performance and fabricating difficulty. In this paper, some typical membrane structures with different dimensions are simulated. Through making finite element analysis to these simulations and comparing of the results, we find out useful information such that foldaway and spiral cantilevers can achieve longer length in the same membrane area; the longer cantilevers are, the smaller electrostatic force is needed, accordingly the bias voltage is lower and the membrane curvature is smaller, etc. Then we use the information to analyze some important factors affecting membrane’s physical and optical performance and make an optimum design.

The inhomogeneous silicon cantilever beam is used to the design of micro-relay, compared the properties with the inhomogeneous and homogeneous cantilever beam, we get the results as: the inhomogeneous cantilever beam has a lower drive power than that of homogeneous; when the same drive power, the pressure of the touch point of the inhomogeneous cantilever is greater than that of homogeneous, but the frequency of the inhomogeneous cantilever is lower than that of homogeneous. In some special cases, if the frequency and dynamic response does not require high precision, the inhomogeneous cantilever beam is a good choice; it can obtain a low driver power and high pressure on the touch point for the micro-relay. The deflection of and the frequency of the analysis of the inhomogeneous silicon cantilever beam for micro-relay is put forward in the paper.

In the MEMS world, increasing attention is being given to 3D devices requiring dual-sided processing. This requires lithography tools that are able to align a wafer to both its back side as front side. Overlay describes how well front and back side layers are positioned with respect to each other. Currently there is no simple and fast method to qualify the overlay. This paper covers a method of measuring the overlay between front- and back side patterns using a glass substrate. We describe the methods used, special process requirements and measurement data. The main advantages of the presented method are the simplicity of the concept and the need for only basic fab processing equipment. The substrate employed is re-usable and low cost. The results are as follows: 1. Glass wafers can be used to measure front to back side overlay. The accuracy of the proposed method is better than 100 nm (3σ) on ASML PAS 5000/5200 machines. On ASML PAS 5500 steppers, the expected accuracy is better than 80 nm (3σ). 2. The proposed method of measuring the absolute glass shift, from a glass-on-silicon stack, yields unreliable information. This is due to deformation of the glass. An alternative method is described which builds on result 1 (above). 3. Processing of glass wafers has been established, and a glass overlay measurement wafer has been defined. 4. The benefit of Anti Reflective (AR) coatings is suspected, but not yet proven. Minimizing bi-refringency does not play a role in the measurement accuracy of glass wafers for overlay measurements.

To provide useful insight into the reliability of silicon micromachined resonator, a measurement system of resonator vibration is presented to check the dynamic characteristics of resonator. The system utilizes heterodyne laser Doppler techniques and acquires the relation between resonator motion and Doppler shift of scatter beam. The vibration principle of resonator was expatiated detailedly and a special driving control circuit was also designed. Experiments on driving and measuring double-ended tuning fork vibration were carried out. The frequency of driving signal is 2.4 kHz and the peak-to-peak value of driving voltage is 140 V. Experimental results indicate that the system can measure dynamic characteristics of Micro-electro-mechanical system (MEMS) well.

In this letter,a InP-based micromechanical tuneable filter by electrostatic actuation is introduced. Through simulation of the DBR reflectance spectra and the F-P cavity transimission spectra,the filter performance is studied. By means of finite element method,the tunning characteristics of the filters based on several typical micromechanical structures are presented. The dynamical behavior of the top mirror is investigated.In addition,the flatness of the top mirror are compared among these structures. It would be valuable reference for InP-based micromechanical F-P cavity device design and optimization.

A new type microaccelerometer with magnetorheological (MR) fluids is presented in this paper. MR fluids can easily change from a fluid state to a semi-solid state in milliseconds when exposed to magnetic field. They are applied to the microaccelerometer where the MR fluids can vary the relative dielectric constant and provide damping. Then the electrostatic force has been adopted in the microaccelerometer for balancing force. Therefore, the measurement range of the microaccelerometer will be expanded. The mathematical model of the microaccelerometer with MR fluids is derived. The curve of the accelerometer between the deflection of the silicon doubly-supported beam and voltage has been simulated. The curves of the accelerometer between the voltage and the acceleration are also got. Last, the stability of the microaccelerometer system has been analyzed.

Technologies for handling, sorting, and positioning of embryos are increasingly important in biomedicine. In this paper the status for ongoing projects aimed at developing instrumentation for high-throughput treatment of embryos is reviewed. Techniques for positioning of Drosophila (fruit-fly) embryos in 2-D arrays for use in microinjection experiments are especially focused. A method based on fluidic micro assembly is discussed, and important parameters such as immobilization yield, the number of misplaced embryos, and adhesion force of the embryos are reported. A model for the assembly process is described, and simulation results are in good agreement with adhesion force measurements. A fully automated MEMS based system for fruit-fly embryo injection has recently been demonstrated at Stanford University. The first experiments with double-stranded RNA injection proved successful, and the expected genetic modification of the embryos was observed.

A new kind of torsion-mirror optical actuators with compound driving structures is reported. The advanced compound driving structures are made up of plate-electrode couple drives and vertical comb drives, and are proved experimentally to be able to actuate mirrors to achieve not only large-range continuous rotation but also 90° rotation. A set of surface-and-bulk-mixed-silicon-micromachining process has been developed to manufacture the new torsion-mirror optical actuators in SOI wafers. In the processing, the comb fingers of about 180 μm in depth are produced. A synthetic coupling-loss model for the coupling system composed of the mirrors and the input and output fiber ends is obtained when the torsion-mirror actuators are brought into use as optical switches or attenuators, etc. for fiber communication applications.

A high-g overload protected piezoresistive accelerometer with the cave form section and two-end-fixed beams was introduced in this paper. Based on the finite element method (FEM) simulation, an optimal design of the microstructure was presented. The accelerometer was fabricated by standard IC process, ICP plasma etching and silicon anodic bonding technique. The testing results show that the accelerometer can bear 20,000g shock, the non-linearity reaches to 0.5% in the ±50g full scale, sensitivity reaches 0.8mV/g, and the operation frequency range is from DC to 2kHz.

Silicon micro-cantilever resonators are typical elements in micro-electro-mechanical systems. Basing on the photothermally excited micro-cantilever resonators, many optical microsystems can be realized, such as micro-swichtes,mciro-modulators and microsensors etc. In this paper, mechanism and experiment study is given on photo-thermally excited bi-layered silicon micro-cantilever resonators, and relative results can be served as the basis of further applications. When coating is put on the surface of micro-cantilever to increase the optically exciting efficiency, the whole resonator becomes bi-layered structure, and the mechanism of this bi-layered resonator is very different from those of single material resonators. In this paper, photo-thermally excited mechanism of bi-layered silicon micro-cantilever was presented and a corresponding photo-thermal theoretical model was set up based on the photo-thermal effect. The first three resonant modes of the silicon micro-cantilever were detected successfully by using piezoelectric resistors fabricated as a Wheat-stone sensing bridge on the micro-cantilever. A novel method was presented to excite and detect the microresonator at the same time by using only one optical source , and this novel method was demonstrated by detecting the first resonant mode of the micro-cantilever.

We describe the design of novel fuel atomizers with a unique internal spiral-conical structure for turbine engines and other propulsion systems. The atomizers are developed using a unique combination of two recently developed technologies: polymer-derived ceramics and an invert microstereolithography process. The polymer-derived ceramics are stable up to high temperatures (1500~1800ºC) and have excellent mechanical and thermal properties. Thus, fuel atomizers made from these materials can be used at high temperatures and have higher corrosion resistance. Invert microstereolithography is a recently developed 3-D microfabrication process that enables complex 3-D structures to be built with high dimensional precision (1µm). The resulting atomizers have many advantages, including stability at high temperatures, high resistance to corrosion, a unique structure for efficient sprays, low cost and amenability to batch manufacturing. With the success of our earlier investigation and recent development, we are able to develop novel atomizers that will fill an immediate need for propulsion systems and many other high-temperature applications. In the future, we will integrate the atomizers into combustion systems and perform physical demonstration of the complete fuel injection system on a representative engine platform for a range of operating conditions.

This paper presents the design, fabrication, and testing of a single crystalline silicon (SCS) micromirror array (MMA) for peptide synthesis applications. Also, preliminary peptide synthesis experiments are presented for the proof of MMA performance. The application specific MMA had a simple fabrication process (only 3 photomasks), large mirror size (210x210μm²) and proper separation (60um). In order to obtain reliable structure and characteristics, we incorporated silicon on insulator (SOI) wafer and stepper photolithography. To maximize the pull-in voltage uniformity, sequential designing steps were described considering design limitations. The proposed fabrication process showed that the fabrication yield was very high up to 91.3%. The total array size consisted of 16 x 16 mirrors and tilting angle was 8.5° for left side or right side operations. The surface roughness was very low and less than 4 nm. The switching time of 156 μsec was reasonable since the exposure time during peptide synthesis was a few seconds. The fabricated MMA had a little pull-in voltage non-uniformity because of dimensional non-uniformities or fabrication errors. We have implemented an automated pull-in voltage measurement setup for verifying the pull-in voltage variation among the array. The measured pull-in voltage among 256 mirrors had the average of 96.99 V and the standard deviation of 2.12 V. The fabricated and analyzed MMA was adapted to the automatic peptide synthesis system and the peptide synthesis experiments showed that the SCS MMA improved the synthesis performance.

We report on an original design and fabrication of microfluidic dye laser integrated into a functional poly-dimethylsiloxane (PDMS) lab-on-a-chip system. Soft lithography has been used for the fabrication of the microfluidic channels allowing the liquid dye circulation. The laser cavity, formed by two cleaved optical fibers with end face metallization, is directly integrated into a microfluidic channel. The active dye molecules are optically pumped by a pulsed and frequency-doubled Nd:Yag laser at 532 nm wavelength. Finally, the output laser beam is extracted and coupled into the optical fiber. As a result, the characteristics of the laser output power as a function of pumping energy density is presented. We also show that the micro dye laser we fabricated can work steadily with an average output power up to 0.35 mW. The wavelength tunability is also demonstrated with the laser system.

Development of microfabrication technologies for MEMS and MOEMS has been reviewed. Depending on the materials, the fabrication technologies are grouped into silicon and non-silicon processes. Inherited from semiconductor industry, silicon process technology is the dominant technology in manufacturing MEMS and MOEMS. Past and present progresses in silicon micromachining have been described. However, there is a growing trend for non-silicon materials in MEMS and MOEMS devices and systems. Variety of materials can be used, including metals, polymers, glass, ceramics, etc. They often offer better performance and low cost of manufacturing than silicon. Although in research community new microfabrication technologies are constantly being developed, the industry requires as few as possible processing technologies so that the complexity and cost of manufacturing can be greatly reduced. MEMS industry needs standardization so that it can prosper like the semiconductor industry. However, there are great hurdles in standardizing MEMS fabrication technology. The fragmented market and diversity of applications make the standardization much more difficult than the semiconductor industry. One formula of standardization is the establishment of foundries. It has been a magic formula for semiconductor industry, but has not been so magic to the MEMS industry.

The microneedle for blood extraction and painless injection is a rapidly growing area of interest in bio-applications. Two new types of microneedle array are designed and developed for biomedical application. The one is hollow PMMA microneedle array with very shape tip fabricated by two times X-ray lithography (one time is with X-ray mask and one time is without X-ray mask). The other is PMMA microneedle array with tips and fluid channels fabricated by an X-ray lithography technique. The resist stage of the X-ray system driven by actuators is to realize movement lithography.

Anisotropic reactive ion etching of silicon has been widely used in fabrication of diffractive optical elements, waveguides and structures of Micro-Electro-Mechanical Systems (MEMS) in recent years. It is important to achieve minimal roughness on both horizontal surfaces and sidewalls in reactive ion etching (RIE) of silicon. Now reactive ion etching of silicon in an RF parallel plate system, using SF₆/O₂/CHF₃ plasmas, has been experimentally studied. Black silicon method (BSM) is a powerful tool that can be used to find the best conditions under which the anisotropic etching of silicon is optimized. In the process of etching silicon, SF₆ serves as the major reactive etching species on silicon, while O₂ is added to build the passivation layer on the sidewalls and surfaces to get anisotropic profiles and CHF3 to suppress the formation of passivation on horizontal surfaces in order to achieve smooth etch surfaces. BSM provides a convenient way to know the function of the gases adding into the RIE and to find how to adjust the proportion of the gas combination. Experimental parameters including the etching rate, selectivity, anisotropy, and self-bias voltage under different parameters have been examined through SEM and AFM. As a result, anisotropic etching conditions and the parameters corresponding to the minimal roughness on the surfaces were obtained.

The formation of deep macropore array of p-type Silicon in HF electrolyte has been investigated. Then a series of electrochemical etching experiments and tests were carried out in three poles electrobath using different concentration HF electrolyte. HF concentration is a very important factor that determined whether electrochemical reaction was accomplished or not. By means of theoretical analysis and investigation, it is generally assumed that etching proceeds through sequential reaction of Si-H groups with F^- to form Si-X, which determined whether electrochemical etching reaction was carried out or not. The electrochemical etching of p-type Silicon macropore array in aqueous fluoride solutions is satisfied with economic requirements for costs of fabricating deep macropores. The consequences are benefit to Silicon electrochemical deep macropore array etching technology.

As laser microfabrication develops fast more and more micro parts of MEMS are produced with laser micro processing technology. Excimer laser ablation is a versatile tool for the micro machining of various materials. Excimer laser materials processing, which is performed in most cases using a mask projection system forms a 3D shape by ablation material. Recently a large number of articles about polymer ablation with excimer lasers have appeared. However the powder material especially metallic powder is paid little attention in excimer laser micro machining. In this paper several types of powder material are investigated in excimer laser ablation. The ablation rate of different powder materials with various fluence ranges, wavelengths, and pulse lengths are studied in experiment. The parameters of excimer laser were optimized to fabricate a micro part. The diameter of about 100 micron gear made of nano powder was finally produced with a mask project system using nanopowder. This method is more efficient than laser writing with a focal spot.

Grating waveguides were fabricated based on Nano-imprint lithography (NIL) and silicon mould replication techniques in this paper. Using a silicon mould repeatedly, low-cost grating waveguides can be fabricated in batches. The proposed grating waveguide is soft enough to be an optical sensing element for catheter, smart skin sensing unit of micro-robots, and etc. Further, these grating waveguides were coupled with optical fibers for its convenient applications. There are two main parts in this paper, the first is to fabricate a suitable silicon mould for replication of grating waveguides, and the second is to reprint grating waveguides by using the fabricated silicon mould. Basing on NIL technology proposed in 1995 by Professor Stephen Y Chou, silicon moulds of grating waveguides with pitch 0.75μm were fabricated on (100) silicon wafer. There are several methods to carry out the replication process, such as Hot embossing, Injection moulding, UV-replication and Casting moulding method. In this work, UV-replication and Casting moulding method was selected to fabricate the grating waveguide structures for its easy control and high fidelity. There are two associated challenging issues in the replicating process; one is to prevent the replicated materials from sticking to the mould for easily peeling off the replicated structure, the other is to find matching materials for the waveguide core and cladding to guarantee the optical characteristics of the grating waveguide. Grating waveguides with core size 4μm×20μm were fabricated successfully in this paper that demonstrated the novel idea of this paper.

A novel micro-fabrication technology using optical radiation pressure is presented. A simulation program has been written and simulation results have demonstrated that micro silica or diamond particles, trapped by focused laser beam, could be used as micro-fabrication tools for nanometer manufacturing. An experiment setup for laser trapping has been established and Silica particles, with diameter of 8 μm, has been successfully trapped in water and arbitrary-shaped diamond particles, whose size is about 3-8 μm, has been trapped and rotated as micro-fabrication tools. When trapped rigidity micro-particles tools was controlled by laser beam, the work stage was horizontally moved repeatedly so that a machining trace of 2nm on work piece has been attained.

Multi-photon absorption phenomena induced by ultra fast laser have been considered for many applications of microfabrications such as metal ablation, glass etching and photopolymerization. Among the applications, the photopolymerization by two-photon absorption (TPA) has been regarded as a new microfabricating method. It is possible to be used in photo mask correcting, diffractive optical element and micro machining. The TPA photopolymerization is made possible to fabricate a complicated three dimensional structure which the conventional photomask technology has not been able to make. Furthermore the TPA photopolymerization process applied to a two dimensional structure fabrication may take shorter time than the old process since the absence of etching and deposition processes. Recently we have made a simple 3D structure and applied the technique to PDMS(poly-dimethyl siloxane) molding.

An optical MEMS pressure sensor based on multi-layer circular diaphragm has been analyzed by utilizing the shell theory and characteristic matrix methods. Finite element methods are used to analyze the deflection of circular diaphragm with the residual stress effect considered. Simulation results are given by using FEM software tools ANSYS. The analytic expressions for the absolute reflectance of multi-layer circular diaphragm structure are derived. The results are valid for the most optical MEMS pressure sensors based on Fabry-Perot interferometer.

In this letter, we propose the new theoretical investigation on the optical forces and torques on complex microrotors. On the basis of R. C. Gauthier’s hybrid ray-wave model, the optical forces and toques on two complex asymmetric micro-objects, the conical microrotor and the helical microrotor, are analyzed. The viscous drag torque is estimated by Stokes flow to obtain the rotational speed. The results of our computation agree well with the previously published experimental results, which indicates that our approach of the optical torque calculation is suitable for other complex microrotors and that the theoretical calculation is very helpful to optimum design of light-driven microrotors.

The prevailing micromachined vibratory gyroscope typically has a proof mass connected to the substrate by a mechanical suspension system, which makes it face a tough challenge to achieve tactical or inertial grade performance levels. With a levitated rotor as the proof mass, a micromachined rotational gyroscope will potentially have higher performance than vibratory gyroscope. Besides working as a moment rebalance dual-axis gyroscope, the micromachined rotational gyroscope based on a levitated rotor can simultaneously work as a force balance tri-axis accelerometer. Micromachined rotational gyroscope based on an electrostatically levitated silicon micromachined rotor has been notably developed. In this paper, factors in designing a rotational gyro/accelerometer based on an electrostatically levitated disc-like rotor, including gyroscopic action of micro rotor, methods of stable levitation, micro displacement detection and control, rotation drive and speed control, vacuum packaging and microfabrication, are comprehensively considered. Hence a design of rotational gyro/accelerometer with an electroforming nickel rotor employing low cost UV-LIGA technology is presented. In this design, a wheel-like flat rotor is proposed and its basic dimensions, diameter and thickness, are estimated according to the required loading capability. Finally, its micromachining methods based on UV-LIGA technology and assembly technology are discussed.

This paper presents a parallel dynamic passive valveless micropump, which consists of three layers-valve, diaphragm and electromagnetic coil. The valve is wetly etched in a silicon wafer, the diaphragm is a PDMS (polydimethyl siloxane) film spun on a silicon wafer with embedded permanent magnet posts, and the coil is electroplated on a silicon substrate. Under the actuation of the magnetic field of the coil, the flexible diaphragm can be displaced upwards and downwards. After analyzing magnetic and mechanical characteristic of the flexible membrane and direction-dependence of the diffuser, this paper designed a micropump. And the relative length (L/d) of the micropump’s diffuser is 4.An 7×7 array of permanent magnetic posts is embedded in the PDMS film. Two diaphragms work in an anti-step mode, which can relieve the liquid shock and increase the discharge of the micropump. ANSYS® and Matlab® are adopted to analyze the actuation effect of the coil and the flow characteristic of the micropump. Results show that when actuated under a 0.3A, 100Hz current ,the displacement of the diaphragm is more than 30μm, and the discharge of the micropump is about 6μL/s.

In this paper, the grating light valve (GLV) is presented. A simple method based on multi-beam of light interference theory is put forward to analyze its optical performance. Computer simulation demonstrates that the dimension of its structure and light source have different influence on the diffractive efficiency. According to detecting system, the diffractive efficiency in the OFF state is about 3.8544x10^-16 at the wavelength of 0.66um, about 2.8218x10^-16at the wavelength of 0.5145um, 1.7846x10^-16at the wavelength of 0.488um, which should ideally be zero. The result indicates that such method applied in the analysis of the GLV is agreeable and simpler. In order to gain higher diffractive efficiency, the air gap should be reduced.

A novel micro fluid oscillator with a boron diffused resistor is proposed in this paper. The actuation principle is based on the combination of Marangoni effect. The contemporary microfabrication technique enables us to fabricate microheater tiny enough to control temperature so quickly and precisely in micro length scale. The devices exhibiting the Marangoni effect in square channels were designed and fabricated from one silicon substrate and two quartz substrates. And the three substrates were aligned, bonded and packaged for testing. In this actuator there is a pair of micro-heaters to produce a thermal gradient along the slit. The driving wattage is about 0.1W and the resistors can make a temperature difference about 100 degrees during 0.1s with a pulsewidth of 20us for 0.1A current pulses. Then the movement is driven towards the lower temperature direction by the interfacial tension of the air-liquid interface. This micro fluid actuator can play important role in many liquid micro-systems such as in micromotor and micro valve.

The excimer laser was used to perform precise machining of optic fiber to form FBG for fiber optic sensing. The influence of various H₂-loading conditions to the photosensitivity of fiber and performance of FBG have been studied, and the temperature sensing properties of the FBG have been investigated. The results show that the photosensitivity of the fiber is determined by hydrogen concentration and the refractive index changes of fiber increases dramatically with the increase of treatment times and finally become saturated. Therefore, the grating reflectivity of the fiber can be controlled by adjusting hydrogen-loading pressure and H2-loading times. The results also show that when the FBG was used for temperature sensing, the Bragg wavelength of the grating is linearly dependent on the environment temperature and the repeatability is good, which indicate that this kind of FBG are appropriate elements to fabricate fiber optic temperature sensors and their systems.

Since the 1970’s, the focused laser beam has become a familiar tool to manipulate neutral, dielectric micro-objects. A number of authors, including Higurashi and Gauthier, have described the effects of radiation pressure from laser light on microrotors. Collett, et al. developed a wave, rather than a ray optic, approach in the calculation of such forces on a microrotor for the first time. This paper describes a modification to the design of a laser driven, radiation pressure microrotor, intended to improve the optically generated torque. Employing the wave approach, the electric and magnetic fields in the vicinity of the rotor are calculated using the finite difference time domain (FDTD) method, which takes into account the wave nature of the incident light. Forces are calculated from the application of Maxwell’s stress tensor over the surfaces of the rotor. Results indicate a significant increase in torque when the index of refraction of the microrotor is changed from a single value to an inhomogeneous profile. The optical fiber industry has successfully employed a variation in the index of refraction across the cross section of a fiber for the purpose of increasing the efficiency of light transmission. Therefore, it is hoped that various fabrication methods can be utilized for causing desired changes in the index of refraction of an optically driven microrotor. Various profiles of the index of refraction inside a microrotor are considered for optimization of torque. Simulation methodology and results of torque on a microrotor for various profiles of the index of refraction are presented. Guidelines for improvised fabrication of efficient microrotors may then be obtained from these profiles.

This paper reports a novel freestanding stencil bi-material cantilever structure without sacrificial layer process in detail; the complexity and costs of fabrication process are reduced greatly. This type of microcantilever is made of two material layers (SiNx/Au), which is a 2dimension device, not a 3dimension one. The cantilevers and the support points are at the same plane in the stencil structure. MEMS sacrificial layer process problems are avoided completely in the process of the freestanding stencil bi-material cantilever microstructure so as to simplify process steps. Since two materials selected in the bi-material cantilever have a large mismatch in thermal conductivity and expansion coefficient, and all cantilevers in the device are freestanding completely, this kind of device is sensitive to a lot of physical varieties, such as thermal, infrared, mechanical vibration and electronic signals. This paper illuminates the total fabrication process of freestanding stencil bi-material cantilever structure; and in particular presents an application of uncooled infrared imaging system based on the novel freestanding bi-material cantilever structure in the final part of this paper.

LIGA process technique is a three-dimensional micromachining technology which is applied to fabricate 3D micromechanical parts. Because the LIGA process requires LIGA mask for deep-etch X-ray lithography, the mask fabrication is a complex technique. The use of micro optical systems in commercial applications (as sensors or in telecommunication) is not only depending on the performance but also on the price of the system. It is highly dominated by fabrication and assembly costs. In order to solve this problem, many efforts have been made in the world. Direct laser patterning of absorber thin films of LIGA mask allows the possibility of rapid prototyping and low cost manufacture of X-ray lithography mask. Excimer laser mask projection techniques have been used in order to directly manufacture LIGA mask for X-ray lithography. The mask pattern with circles structures with 25µm pitch have been fabricated by sequential direct laser ablation of thin gold film using mask projection techniques. This paper describes the X-ray mask design and fabrication processes in details. The fabricated LIGA mask is used as a pattern for x-ray exposure onto a polymethyl-methacrylate (PMMA) resist. A fine micro structures of PMMA in a low cost and a short fabrication period is obtained using the mask. It is confirmed that such LIGA mask is important for rapid prototyping in the areas of medical and biosensors.

We study insertion losses of optical switch when the laser beam is propagating during the free space between two single mode fibers (SMFs) and the related assemblage challenges; Then a new packaging structure is developed for the hybrid-integration of free-space MOEMS (micro-opto-electro-mechanical systems) chip with a silicon micromachined submount to improve alignment accuracy. The submount is designed to accommodate various free-space MOEMS chips with minimal active optical alignment, thus reducing the packaging cost. The silicon submount has a central recess to place the MOEMS chip in, sixteen V-grooves for optical fibers, and micropits for micro ball lenses, all bulk micromachined at the same time by a single anisotropic wet etching step. A corner compensation technique is employed to prevent erosion of the convex corners, where different geometries meet. Through this assembling method, the fiber, micro ball lens can be aligned preciously thus reduced lateral and angular misalignment between them. Then total insertion losses can be decreased.

Experimental and theoretical analysis indicates that many nonlinear factors existing in the exposure process of thick resist can remarkably affect the PAC concentration distribution in the resist. So the effects should be fully considered in the exposure model of thick resist, and exposure parameters should not be treated as constants because there exists certain relationship between the parameters and resist thickness. In this paper, an enhanced Dill model for the exposure process of thick resist is presented, and the experimental setup for measuring exposure parameters of thick resist is developed. We measure the intensity transmittance curve of thick resist AZ4562 under different processing conditions, and extract the corresponding exposure parameters based on the experiment results and the calculations from the beam propagation matrix of the resist films. With these modified modeling parameters and enhanced Dill model, simulation of thick-resist exposure process can be effectively developed in the future.

This paper reports on a silicon micro-hole arrays (Si-MHA) prepared by Inductively Coupled Plasma (ICP) etching, a dry etching method. By ICP etcher, we carried out several experimental researches and process exploration for micromachining Si-MHA. The mechanism of lateral etching, sidewall passivation, gas micro-transport and some process parameters in Si-MHA micromachining, such as gas switching time, flow rate, etching rate, were analyzed. The footing effect, lag effect, longitudinal strips and RIE grass effect occurred in the ICP etching process were also studied. These process problems had reappeared in the micro-hole arrays process though these problems had be solved in the field of integrated circuits process and microelectromechanical system (MEMS). The study results reported here had demonstrated a Si-MHA that the diameter was 15 μm, the center distance 30 μm, and the depth 240 μm prepared by ICP, and had led the author to believe that the deep pore structure and the deep trench with high aspect ratio were very different in etching process. The former is a closed structure for the gas transport, and the latter is an open structure, so the process of deep hole structure is a puzzle in micromachining and MEMS technology.

The recent progress in large-range and nanoscale micromotion stages is summarized, and a novel magnetic levitation stage that can provide large range motion with nanometer positioning accuracy is proposed in this paper. The construction, dynamics analysis, measurement system, and control strategy of this stage are presented and discussed.

There are many micro-fabrication technologies. Some micro-components can be fabricated by selective laser sintering (SLS). When selective laser sintering metal powders is used to produce micro-components, there are numbers of factors which will influence final result, such as laser wavelength, laser power, diameter of laser beam, scanning speed, particle size and materials etc. These factors are not single but interfere with each other. The change of one factor will greatly affect the character of final micro-components (such as width of scanning track , dimension error, component hardness ,etc). In selective laser sintering metal powders, many experiments are needed in order to get the optimum process parameters. However, this will cost much time and money. Moreover in later process, new experiments will be needed in order to get the optimum process parameters due to the change of one factor. Many models about selective laser sintering metal powders have been investigated in the past. Nevertheless, these models are about the interaction of laser and metal powders, and the physical and thermal response to the initial condition. They are provided for the macro-fabrication. No model can be applied in the micro-domain, and no one aims at the influence of these factors on the character of the final micro-component. In this paper a numerical model about the relation of these factors and the character of final micro-components is provided to minimize the number of experiments. This model will include the major factors of SLS in micro-domain, and through such a model we can deduce the numerical value of optimum process parameters from final micro-component character instead of making a lot of process experiments. Therefore the cost of micro-fabrication with SLS techniques will be greatly reduced.