Materials,effects and components for tunable micro‐optics

An overview of recent activities in the area of tunable micro‐optical components is given. These include polymer‐based deformable mirrors for adaptive optics, tunable microlenses and arrays using fluids and membranes, pneumatically actuated scanning micromirrors and tunable Bragg filters and mirrors using swelling polymers. For each device, the structure, essential fabrication technology and optical characteristics, as well as a discussion of application areas are presented. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Transparent biosensor with micro channel array for optical and electrophysiological detection of luciferin–luciferase reaction

This paper describes a transparent biosensor that was designed to detect both the optical and electrophysiological signals of the luciferin–luciferase reaction. By using microelectromechanical system (MEMS) technologies, we have studied and developed a ‘Micro Channel Array’ (MCA) integrated with suction holes and electrodes as planar patch‐clamp biosensors. A transparent biosensor was developed as an advanced MCA. The developed transparent biosensor employs an SU‐8‐based MCA structure for simultaneous multipoint sensing of optical and electrophysiological signals. In this study, we tested the newly developed biosensor using the mPer1‐luc slice culture, which has circadian rhythms and is a typical example of cells in which a luciferin–luciferase reaction occurs. We could measure the optical and electrophysiological signals of the mPer1‐luc slice culture. Here we describe the experimental results of this study, and describe the design and fabrication of the transparent biosensor with MCA. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

RF MEMS technology

Recently, to meet the demands of multimode/multiband functions for the next generation communication systems, RF MEMS technology is being developed for the reconfigurable transceiver system. In this article, RF MEMS devices such as switches, high‐Q inductors, and high‐Q resonators are reviewed for their operating principles and device structures, as well as the reliability and commercial issues. Single pole single throw (SPST)‐type MEMS switches show characteristics superior to solid‐state switches in the aspects of insertion loss, isolation, and linearity. Single pole multithrow (SPMT) switches will enable ultra small‐sized cellular phones, but insertion loss and coupling between channels should be improved. For a high‐Q inductor, out‐of‐plane inductors show improved results, and an inductor with a Q‐factor of 75 at 1GHz has been fabricated by using the internal stress of a MoCr film. The MEMS inductor improves the performance of a voltage controlled oscillator (VCO), but proper hermetic packaging and standard libraries are also necessary for mass production. The MEMS resonator can operate up to 1.4 GHz and can be used as an oscillator for the timing device as well as component of the filter circuit. The SiTime Company recently has started delivery of a product with performance similar to the quartz oscillator, in which they solved the reliability issues by modifying the annealing and vacuum packaging. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Design and modeling of compliant micromechanism for mechanical digital‐to‐analog conversion of displacement

A microelectromechanical digital‐to‐analog converter (MEMDAC) converts digital motion of shuttle actuators operated by the corresponding bits of a binary code into an output displacement proportional to the analog value represented by the input code. In this paper a MEMDAC with improved kinematic design is devised that allows large travel range and high positioning resolution while making the microfabrication process less critical. A lumped‐parameter model of the compliant mechanism of an N‐bit MEMDAC is derived and used to determine the stiffness ratio of flexible members needed for proper mechanical digital‐to‐analog conversion. Furthermore, we analytically investigated the effect of nonuniformity in the device geometry due to the limitations of the microfabrication processes on the linearity of the output displacement. Successful fabrication and release of a 12‐bit MEMDAC demonstrated the manufacturability of the new mechanism, revealing opportunities for MEMS applications in which micropositioners with open‐loop operation, relatively large output range, fine positioning resolution and high repeatability are required. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Towards mechanical characterization of biomolecules by MNEMS tools

Single‐molecule micromanipulations have provided information that has been awaited for a long time. However, these experiments relying on optical tweezers (OT) or magnetic tweezers (MT) have a low throughput since the molecular preparation is done one at a time. In order to move towards systematic biological or medical analysis, micro‐nano‐electromechanical systems (MNEMS) are the appropriate devices, as they integrate accurate molecular level engineering tools and can be cheaply produced with highly parallel fabrication processes. This paper investigates the ability of MNEMS tweezers to perform molecular manipulations. The mechanical forces relevant in biological interactions are first reviewed and compared to the performances of biophysical instruments. MNEMS tweezers are then presented. The tweezers integrate opposing sharp tips to capture the molecules, an actuator to stretch them and a displacement sensor to measure in real time the produced molecular extension. DNA molecular bundles are readily assembled and manipulated. The sensor provides a 0.3‐nm stretching resolution, equivalent to the interbase pair distance in double‐stranded DNA. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A behavioral model for optically powered OCT endoscope with a micro electrostatic vertical‐comb optical scanner

This paper presents a novel device architecture for optically actuated microelectromechanical systems (MEMS) endoscopes for optical coherence tomography (OCT) measurement. A 10‐mW infrared light beam at a wavelength of 1.5 µm is transferred through the single‐mode fiber to provide a scanning MEMS mirror with the drive voltage (maximum 11 V) by exciting a photovoltaic cell, while also providing with a secondary light beam at a wavelength of 1.3 µm for the OCT measurement. An electrostatic vertical comb‐drive optical scanner (1.5 mm × 2.0 mm × 0.5 mm) has been developed by using the deep reactive ion etching (DRIE) of a silicon‐on‐insulator (SOI) wafer. The design of the scanner module is discussed, along with the experimental results of electrostatic operation. An equivalent circuit model for the optical scanner is developed to explain the behavior of the optically powered actuation mechanism, including the hysteresis loop in the frequency response and the voltage dependence of oscillating angle (mechanical peak ±3.2°/7 V around the resonance frequency of 250 Hz). OCT measurement of a tissue is demonstrated to reconstruct the cross‐sectional image of a fingerprint at a resolution of lateral 40 µm × vertical 8 µm and penetration depth of 2.5 mm. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Development of radio frequency transmitters including on‐chip antenna for intelligent human sensing systems

This paper presents the essentials of the development of an integrated smart microsensor system that has been developed to monitor the motion and vital signs of humans in various environments. Integration of RF transmitter technology with complementary metal‐oxide‐semiconductor/micro electro mechanical systems (CMOS/MEMS) microsensors is required to realize wireless smart microsensors for the monitoring system. Sensors for the measurement of body temperature, perspiration, heart rate (pressure sensor), and motion (accelerometers) are candidates for integration on the wireless smart microsensor system. In this paper, the development of radio frequency transmitter (RF) that will be integrated on wireless smart microsensors is presented. A voltage controlled RF‐CMOS oscillator (VCO) has been fabricated for the 300‐MHz frequency band applications. Also, spiral inductors for an LC resonator and an integrated antenna have been realized with a CMOS‐compatible metallization process. The essential RF components have been fabricated and evaluated experimentally. The fabricated CMOS VCO showed a conversion factor from voltage to frequency of about 81 MHz/V. After matching the characteristic impedance (50 Ω) of the on‐chip integrated antenna and the VCO output, more than 5 m signal transmission from the microchip antenna has been observed. The transmitter showed remarkable improvement in transmission power efficiency by correct matching with the microchip antenna. Essential technologies of the RF transmitter for the wireless smart microsensors have been successfully developed. Also, for the 300‐MHz band application, the integrated RF transmitter, with the CMOS oscillator and the on‐chip antenna, has been successfully demonstrated for the first time. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Localized thermal processing with a laser‐trapped and heated metal nanoparticle

We report localized thermal processing using a laser‐trapped and heated metal nanoparticle. A metal nanoparticle trapped by a focused, continuous wave (CW), near‐infrared laser was heated by photothermal conversion and acted as a remotely controllable nanosized thermal tool for processing a workpiece. We demonstrated the processing of a glass substrate with an optically trapped gold nanoparticle (diameter 200 nm) irradiated by a Nd:YAG laser (λ = 1.064 µm, CW). Laser irradiation caused local melting of the substrate and a crater‐like nanosized imprint on the substrate, demonstrating thermal nanoprocessing of an optically transparent material. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Pressure sensing by electrical admittance measurement of a comb‐drive actuator

This paper describes a micromachined pressure sensor that senses pressure not by a diaphragm structure but by a resonantly vibrating comb‐drive actuator. The electrical admittance of the comb‐drive actuator was directly measured using a lock‐in amplifier, and its pressure dependence was examined. From the experiment, it was found that the resonant frequency of the comb‐drive actuator gradually drops as the pressure increases. The sensitivity of the comb‐drive actuator as a pressure sensor was 0.34 Hz/MPa at atmospheric pressure and 0.1 Hz/MPa at 0.4 MPa absolute pressure. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Development of terabit‐class super‐networking technologies

We propose terabit‐class super‐networking technologies, designed to improve the scalability, reliability and performance of optical Internet protocol networks. Our technologies comprise both intra‐ and interlayer traffic engineering technologies. The intralayer technologies include an optical path protection scheme, an electrical load‐balancing scheme and a distributed content‐caching scheme. These provide an effective and economical way of improving performance and reliability. The interlayer technologies include both traffic‐driven and application‐driven optical cut‐through control schemes and a policy control scheme. These provide an effective and economical way of improving scalability and performance. The feasibility of our technologies has been verified by means of experiments using prototype systems. The results showed that the different techniques can be combined to form a single network architecture for dynamic optical path control. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Analysis and design of a MEMS DC/DC converter

This paper presents the analysis and simulation of a microelectromechanical system (MEMS) DC/DC converter based on vibration‐to‐electric energy conversion. The device transfers and accumulates the mechanical energy from ambient vibration via a variable capacitor. After the key parameters of the device are carefully discussed, the dynamics analysis is given based on the differential equation of the system. The approach provided in this paper is very helpful in designing and essentially understanding the MEMS DC/DC converter with high performance. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Exploration of communication models in the design of distributed embedded systems

Distributed embedded systems involve communication in various layers, and therefore their design is more difficult than of single embedded systems. This paper presents how communication exploration can be done in a design process of distributed embedded systems using an example of event‐triggered and time‐triggered communication. A design process begins from abstract specification without assuming any communication category, then explores the categories in a stepwise manner, followed by physical implementation synthesis. This encourages stepwise decision making, component and framework reuse, and early stage verification. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Basic characteristics of a space charge balance sensor using a MOSFET

A new space charge balance sensor was developed in order to control ion generation in an air ionizer. Conventionally, a charged plate monitor is widely used in order to detect the space charge balance of the air ionizer. However, the charged plate monitor is not suitable for the feedback system for several reasons. The proposed sensor, in spite of its very simple structure, can detect the space charge balance instantly with enough sensitivity, with a shorter response time, and has a possibility of higher spatial resolution compared to a charge plate monitor. An air ionizer control system that can generate a specific quantity of ions at desired locations is considered to be easily implemented by using feedback of the sensed signal to the air ionizer. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

High‐sensitivity surface micromachinable accelerometer using a ferroelectric substrate and its characterization

The present study reports the fabrication and characterization of a high‐sensitivity surface micromachinable accelerometer using a ferroelectric material having a large dielectric constant, such as bulk PZT (ε_r = 2600). The measurement principle is the detection of capacitance change with respect to the dielectric mass movement in the fringe electrical field. Considering the practical fabrication, a ferroelectric material is used for the substrate instead of the suspended proof mass. Since capacitance is increased not mechanically but electrically, high sensitivity can be expected while maintaining mechanical stiffness, which has the advantage of preventing touch down of the proof mass and widening the allowable measuring range of acceleration. A fabricated sensor is characterized. A high sensitivity of several sub‐pF/g is confirmed, which is hundreds of times higher compared to that of a sensor fabricated using the Parylene polymer (ε_r = 3.15). This sensitivity is an order higher compared to those of other reported capacitive microaccelerometers, which have comparable proof mass sizes and comparable detectable acceleration ranges to the newly fabricated sensor. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Condition monitoring systems for power equipment using Internet‐based technology

The implementation of Internet technologies in power equipment monitoring systems will allow free and flexible acquisition of power system information and equipment sensor information at remote locations. By utilizing general‐purpose Internet technologies such as IP telecommunication and browser, widely distributed data can be collected easily. This paper introduces the basic configurations of Internet‐based systems and provides examples of where these systems have been implemented. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Basic study of high‐frequency carrier‐type magnetic field sensor using shape anisotropy

We tried to control the magnetic anisotropy of a high‐frequency carrier‐type magnetic field sensor by the shape of the magnetic film instead of induced anisotropy. We confirmed that the impedance of the sensor could be changed by applying a magnetic field. In addition, we tried to control the magnetic anisotropy with magnetostatic energy. We show that the properties of the sensor can be controlled by designing the shape of the magnetic film. © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Advanced silicon microstructures,sensors, and systems

This paper presents the progress in silicon‐based biomedical microstructures, material characterization techniques, and mechanical microsystems by the authors' research team. Microneedle and microelectrode arrays with fluidic through‐wafer vias and electrical contacts were developed. The structures are designed for dermatological and biological applications such as allergy testing, surface electromyography, and spatially resolved impedance spectroscopy. The characterization of thin films has relied on the bulge test. By the formulation of more powerful models, the application range of the bulge test was extended to elastically supported thin‐film multilayers. This enables the mechanical properties of thin films to be determined reliably. Finally, progress in the operation and application of novel stress sensors based on CMOS diffusions and field effect transistors and exploiting the pseudo‐Hall effect is reported. Their integration into powerful single‐chip microsystems is described. Applications include stress mapping, force and torque measurements, and tactile surface probing of microcomponents. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Fabrication of a microelectromechanical system mirror array and its drive electrodes for low electrical interference in wavelength‐selective switches

This article describes the fabrication of a microelectromechanical system (MEMS) mirror array and mirror‐drive electrodes with high‐aspect‐ratio gold walls that reduce electrical interference in a wavelength‐selective switch (WSS). The MEMS mirror array, in which a lot of closely spaced adjacent mirrors are electrostatically operated, can be fabricated with a high yield by encapsulating the mirrors with an organic film that protects them from process damage. The gold walls with a high‐aspect ratio are formed in the narrow space between adjacent mirror‐drive electrodes by using thick‐multilevel interconnection technology. Because of these walls between adjacent electrodes, each MEMS mirror operates with low electrical interference. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

In situ visualization of degradation of silicon field emitter tips

This paper deals with the simultaneous observation of both the electron field emission from nanoscopic tips by electrical means and their structural shape change by an ultra‐high resolution transmission electron microscope (TEM). Nanoneedles with sharp tips of radius in the nanometer range were fabricated with semiconductor micromachining technology. A correlation between the electron field emission characteristics and the structural change of the emitter tip was clearly observed. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Fabrication of metallic nanopatterns using the vacuum type UV‐NIL equipment

Nanoscale dot patterns of cobalt alloy were formed on a silicon substrate using the ultra‐violet nanoimprint lithography (UV‐NIL) technology in combination with an electrodeposition process. We developed an improved UV‐NIL equipment that can evacuate the chamber during imprinting. Using this equipment, we successfully imprinted 240‐nm dot patterns with 500 nm pitch on a photocurable resin with high dimensional accuracy. Thickness control of the resin and imprinting under vacuum are important issues to obtain fine nanopatterns. Using these resin patterns as a mask layer, 300‐nm cobalt alloy patterns are successfully formed by the electrodeposition process. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.