Two-dimensional Microelectromechanical System Research Articles

着陸レーザーレーダ用2次元MEMS光スキャナ

We present the design, fabrication, and demonstration of a two-dimensional MEMS (microelectromechanical systems) optical scanner for a compact laser radar for a spacecraft landing on a planet. Electrostatic force caused by the voltages applied to the comb-like micro electrodes is adopted as an operation principle that is inherently robust to the harsh environment in space. Optical scan angles of 10º × 15º is obtained with drive voltages of 150V.

Analysis of Distortion Based on 2D MEMS Micromirror Scanning Projection System.

To analyze the distortion problem of two-dimensional micro-electromechanical system (MEMS) micromirror in-plane scanning, this paper makes a full theoretical analysis of the distortion causes from many aspects. Firstly, the mathematical relations among the deflection angle, laser incidence angle, and plane scanning distance of the micromirror are constructed, and the types of projection distortion of the micromirror scanning are discussed. Then the simulation results of reflection angle distribution and point cloud distribution are verified by MATLAB software under different working conditions. Finally, a two-dimensional MEMS micromirror scanning projection system is built. The predetermined waveform can be scanned and projected successfully. The distortion theory is proved to be correct by analyzing the distortion of the projection images, which lays a foundation for practical engineering application.

Electrostatic Circular Membrane MEMS: An Approach to the Optimal Control

The recovery of the membrane profile of an electrostatic micro-electro-mechanical system (MEMS) is an important issue, because, when an external electrical voltage is applied, the membrane deforms with the risk of touching the upper plate of the device producing an unwanted electrostatic effect. Therefore, it is important to know whether the movement admits stable equilibrium configurations especially when the membrane is closed to the upper plate. In this framework, this work analyzes the behavior of a two-dimensional (2D) electrostatic circular membrane MEMS device subjected to an external voltage. Specifically, starting from a well-known 2D non-linear second-order differential model in which the electrostatic field in the device is proportional to the mean curvature of the membrane, the stability of the only possible equilibrium configuration is studied. Furthermore, when considering that the membrane is equipped with mechanical inertia and that it must not touch the upper plate of the device, a useful range of possible values has been obtained for the applied voltage. Finally, the paper concludes with some computations regarding the variation of potential energy, identifying some optimal control conditions.

A Study of Correction to the Point Cloud Distortion Based on MEMS LiDAR System

Active imaging technology can perceive the surrounding environment and obtain three-dimensional information of the target. Among them, light detection and ranging (LiDAR) imaging systems are one of the hottest topics in the field of photoelectric active imaging. Due to the small size, fast scanning speed, low power consumption, low price and strong anti-interference, a micro-electro-mechanical system (MEMS) based micro-scanning LiDAR is widely used in LiDAR imaging systems. However, the imaging point cloud will be distorted, which affects the accurate acquisition of target information. Therefore, in this article, we analyzed the causes of distortion initially, and then introduced a novel coordinate correction method, which can correct the point cloud distortion of the micro-scanning LiDAR system based on MEMS. We implemented our coordinate correction method in a two-dimensional MEMS LiDAR system to verify the feasibility. Experiments show that the point cloud distortion is basically corrected and the distortion is reduced by almost 72.5%. This method can provide an effective reference for the correction of point cloud distortion.

Design of Piezo-Resistive Type Acoustic Vector Sensor using Graphene for Underwater Applications

In recent years as the level of radiated noise of submarine drastically got decreased, the requirement of underwater acoustic sensor has become essential for the detection of low frequency acoustic signal. The latest advancement in the field of underwater sensors is the Micro Electro Mechanical Systems (MEMS) sensor. The major advantage of this sensor being determination of directionality along with the measurement of pressure of an acoustic signal. The biological inspiration behind the design of the sensor was derived from fish lateral line sensing system, with piezoresistive transduction principle to obtain the objective of miniaturization and low frequency signal detection. In this paper, we are reporting the design, simulation of an underwater two-dimensional MEMS acoustic vector sensor which exhibits better sensitivity, flexibility when compared to the traditional acoustic vector sensor. In this work, thin film of piezoresistve material, Reduced Graphene Oxide (Rgo) is taken as pressure sensing element instead of traditional polysilicon material and its performance in terms of sensitivity and directivity is analysed. MEMS acoustic vector sensors using Reduced Graphene Oxide and polysilicon were simulated on flexible kapton and silicon substrate respectively using COMSOL Multiphysics 5.5 vesrion. The simulation results indicates that designed vector sensor based on MEMS technology and piezoresistive effect of rGO on flexible kapton substrate is feasible and possesses better sensitivity of -149.47 dB when compared to the sensitivity of -171.37 dB of polysilicon based traditional acoustic vector sensor. The simulated value of eigen frequency of the sensor is found as around 47Hz, which almost matches with the theoretical value of resonance frequency of the sensor as per the design considerations of the sensor and hence capable of detecting low frequency acoustic signals.

Simple retinal imaging system using a MEMS scanning mirror

We have fabricated a simple and compact scanning laser optical system using microelectromechanical system (MEMS) scanner that can be incorporated into portable health monitoring devices. The two-dimensional (2-D) MEMS scanner used in this system is much smaller and light in weight compared to galvanometer scanners and polygon scanners used in the commercially available ophthalmic devices. MEMS scanners have many advantages and also limitations compared to galvanometer and polygon scanners. An easy to use and compact device is more useful for rapid alignment for measurement and data acquisition. Sensitivity of the system was quantified by measuring signal-to-noise ratio (SNR) for both high and low reflectivity materials. SNR was 10 for the high reflectance materials and about 4 for low reflectance materials, which is sufficient for biological imaging. Distortion generated using large scanning angle of 2-D MEMS scanner was corrected in real time by custom made LabVIEW program. Ocular safety is important to consider when using a laser for ophthalmic devices. We calculated the maximum permissible beam power for thermal damage and photochemical damage considering the specification of our system such as visual angle and wavelength of the laser beam. The measured laser intensity in the front of model eye was 6 μW, which is much smaller than the maximum permissible beam power recommended by the American National Standards Institute.

Miniaturized Optical Resolution Photoacoustic Microscope Based on a Microelectromechanical Systems Scanning Mirror.

In this paper, we report a miniaturized optical resolution photoacoustic microscopy system based on a microelectromechanical system (MEMS) scanning mirror. A two-dimensional MEMS scanning mirror was used to achieve raster scanning of the excitation optical focus. The wideband photoacoustic signals were detected by a flat ultrasound transducer with a center frequency of 10 MHz and an active area of 2 mm in diameter. The size and weight of this device were 60 mm × 30 mm × 20 mm and 40 g, respectively. We evaluated this system using sharp blades, carbon fibers, and a silver strip target. In vivo experiments of imaging vasculatures in the mouse ear, brain, and human lip were completed to demonstrate its potential for biological and clinical applications.

Ink-Jet Printing of Micro-Electro-Mechanical Systems (MEMS)

Beyond printing text on paper, inkjet printing methods have recently been applied to print passive electrical and optical microparts, such as conductors, resistors, solder bumps and polymeric micro lenses. They are also useful to print micro-electro-mechanical systems (MEMS) as sub-millimeter sensor and actuator arrays, such as multifunctional skins applicable to robotic application and ambient monitoring. This paper presents the latest review of a few successful cases of printable MEMS devices. This review shows that inkjet printing is good for printing two-dimensional or surface MEMS devices from a small unit to an array over a large area. In the future, three-dimensional printing of multi-materials, from metal, plastic, to ceramic, will open the possibility of realizing more variety and function of a large-areal MEMS array, for a mobile electro-mechanical systems.

GEOMETRICALLY NONLINEAR ANALYSIS OF MICROSWITCHES USING THE LOCAL MESHFREE METHOD

In the modeling and simulation of microelectromechanical system (MEMS) devices, such as the microswitch, the large deformation or the geometrical nonlinearity should be considered. Due to the issue of mesh distortion, the finite element method (FEM) is not effective for this large deformation analysis. In this paper, a local meshfree formulation is developed for geometrically nonlinear analysis of MEMS devices. The moving least squares approximation (MLSA) is employed to construct the meshfree shape functions based on the arbitrarily distributed field nodes and the spline weight function. The discrete system of equations for two-dimensional MEMS analysis is obtained using the weighted local weak form, and based on the total Lagrangian (TL) approach, which refers all variables to the initial configuration. The Newton–Raphson iteration technique is used to get the final results. Several typical microswitches are simulated by the developed nonlinear local meshfree method. Some important parameters of these microswitches, e.g. the pull-in voltage, are studied. Compared with the experimental results and results obtained by linear analysis, nonlinear meshfree analysis of microswitches is accurate and efficient. It has demonstrated that the present nonlinear local meshfree formulation is very effective for geometrically nonlinear analysis of MEMS devices, because it totally avoids the issue of mesh distortion in the FEM.

Three-dimensional in vivo imaging by a handheld dual-axes confocal microscope

We present a handheld dual-axes confocal microscope that is based on a two-dimensional microelectromechanical systems (MEMS) scanner. It performs reflectance and fluorescence imaging at 488 nm wavelength, with three-dimensional imaging capability. The fully packaged microscope has a diameter of 10 mm and acquires images at 4 Hz frame rate with a maximum field of view of 400 microm x 260 microm. The transverse and axial resolutions of the handheld probe are 1.7 microm and 5.8 microm, respectively. Capability to perform real time small animal imaging is demonstrated in vivo in transgenic mice.

A Novel Integrated Multistage 2-D MEMS Optical Switch With Spanke–Benes Architecture

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Due to the emergence of high-capacity wavelength- division multiplexing transmission systems, new optical cross- connect (OXC) architectures that make a large number of fiber/wavelength counts to switch the signal in the optical domain are needed. Optical microelectromechanical system (MEMS) switches are regarded as the most promising optical switch technology to achieve such functionalities. In this paper, we propose a novel integrated multistage two-dimensional (2-D) MEMS optical switch design with Spanke-Benes architecture and compare it with the conventional crossbar architecture, the L-switching architecture, and Shuffle-Benes architecture. Our proposed architecture is very suitable for building large-port-count 2-D MEMS switches and achieves much better performance in terms of beam divergence loss, longest optical path, mirror radius, substrate size, port-to-port repeatability, and power consumption than the other three architectures. Furthermore, compared with the 2-D conventional crossbar switch commercially available now, the proposed architecture can save 50% mirrors, shorten 87.5% longest optical path, minify 65% mirror radius, and shrink 90% substrate size. </para>

Two-Dimensional MEMS Scanner for Dual-Axes Confocal Microscopy

In this paper, we present a novel 2-D microelectromechanical systems (MEMS) scanner that enables dual-axes confocal microscopy. Dual-axes confocal microscopy provides high resolution and long working distance, while also being well suited for miniaturization and integration into endoscopes for in vivo imaging. The gimbaled MEMS scanner is fabricated on a double silicon-on-insulator (SOI) wafer (a silicon wafer bonded on a SOI wafer) and is actuated by self-aligned vertical electrostatic combdrives. Maximum optical deflections of plusmn4.8deg and plusmn5.5deg are achieved in static mode for the outer and inner axes, respectively. Torsional resonant frequencies are at 500 Hz and 2.9 kHz for the outer and inner axes, respectively. The imaging capability of the MEMS scanner is successfully demonstrated in a breadboard setup. Reflectance images with a field of view of are achieved at 8 frames/s. The transverse resolutions are 3.94 mum and 6.68 mum for the horizontal and vertical dimensions, respectively.

Alternative structures for two-dimensional MEMS optical switches [Invited

Feature Issue on Optical Interconnection Networks (OIN). Two-dimensional (2-D) microelectromechanical system (MEMS) optical switches have the merits of easy fabrication and high reliability. Since the optical signal loss is mainly proportional to the length of signaling paths in the switches, current 2-D MEMS optical switches that use a crossbar structure have a rather limited number of ports. For larger 2-D MEMS optical switches, we may use nonrectangular topology switching fabrics to shorten the internal signaling path or to recollimate the optical signal segment by segment inside the switches. We discuss these approaches from the aspect of implementation and routing control complexity.

SOI-based 2-D mems L-switching matrix for optical networking

Two-dimensional microelectromechanical system (2-D MEMS) optical switches have been widely demonstrated in research laboratories and in the industry. A novel switching architecture, the L-switching matrix, that decreases the most distance free space path length and the difference between the most and least distance paths while maintaining nonblocking port switching capacity has been proposed and demonstrated. Collimators with optimized beam waist are selected such that the insertion loss of the average beam path is the lowest. Larger beam waists are used to accommodate for the diffraction effects of the Gaussian beam of the most distance path. However, larger beam waists require larger mirror areas to avoid beam-clipping and losses due to angular misalignment are more acute. Therefore, having shorter absolute and relative path lengths will avoid the beam-clipping effects and increase the port-to-port loss uniformity of the optical switch. The unique architecture of the L-switching matrix which utilizes a double-sided mirror can theoretically increase the maximum port-count to 64×64 or decrease the current insertion loss of a 32×32 MEMS switch by 50%. Moreover, the L-switching matrix requires 25% less mirrors and electrodes than a conventional cross bar architecture. A fabrication process involving silicon-on-insulator (SOI) wafers has been defined to fabricate the double-sided mirrors used in the L-switching matrix.

1D MEMS-based, wavelength switching subsystem

Over the past few years, micro-electromechanical systems (MEMS) have emerged as a leading technology for realizing transparent optical switching subsystems. MEMS technology allows high-precision micromechanical components such as micromirrors to be mass produced at low cost. These components can be precisely controlled to provide reliable high-speed switching of optical beams in free space. Additionally, MEMS offers solutions that are scalable in both port (fiber) count and the ability to switch large numbers of wavelengths (> 100) per fiber. To date, most of this interest has focused on two-dimensional and three-dimensional MEMS optical crossconnect architectures. We introduce a wavelength-selective switch based on one-dimensional MEMS technology and discuss its performance, reliability, and superior scaling properties. We also review several important applications for this technology in all-optical networks.

Architectural design for multistage 2-D MEMS optical switches

Next-generation wavelength routing optical networks requiring optical cross connects (OXC) in the network have the ability to direct optical signals from any input interface to suitable output interfaces by configuring their internal embedded optical switch matrices. Microelectromechanical systems (MEMS) switches are regarded as the most promising technology to achieve such functionality. We consider the construction of a multistage MEMS switch network with single two-dimensional (2-D) MEMS switch blocks. A power loss model is developed that calls on a single MEMS block that is then used to develop the model for a three-stage Clos network. An effective model for maximum loss difference between calls is also developed. Based on these, the paper also proposes three connection patterns [Max + Min greedy (MMG), compressed extended generalized shuffle 1 (C-EGS-1), and compressed extended generalized shuffle 2 (C-EGS-2)] to connect outlet ports and inlet ports between two neighboring stages in a three-stage Clos network. These connection patterns are proved to be optimal and efficient enough to reach the minimums of both the maximum power loss of calls and the maximum loss difference between calls.