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.     

Fabrication of densely arrayed Si needles with large height for transdermal drug delivery system application

The effects of varying etching conditions for microneedle fabrication were investigated in order to form densely arrayed, sharply angled Si needles with large height for application in transdermal drug delivery systems (DDSs). A sharply angled needle shape could be fabricated by using 34.0 wt% KOH (representing a typical etching‐rate diagram at a highly alkaline etching solution concentration). The needle height could be increased by 20% by adding a compensation mask pattern or by increasing the KOH concentration to 51.0 wt%. The trade‐off relationship between the maximum needle height and the needle density was calculated. These experiments provided useful parameters for designing densely arrayed, sharply angled Si needles for transdermal DDS application. 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.     

Novel fabrication method for long silicon microneedles with three‐dimensional sharp tips and complicated shank shapes by isotropic dry etching

This paper proposes a novel fabrication method for long solid microneedles made of silicon, which have a three‐dimensional sharp tip, by using isotropic dry etching. Since the fabrication is done in a direction parallel to the surface of the silicon substrate, there is no limit for the needle length. Also, the shank shape of this needle is freely designed three‐dimensionally by defining the mask on the silicon surface. For example, a jagged or harpoon shape is possible by using the proposed method, which may be effective for some medical applications. First, several three‐dimensional, complicated‐shaped needles with sharp tip angles were fabricated by changing the mask pattern. Second, a penetration experiment with them on an artificial skin was carried out, and easy penetration comparable with a conventional metal solid needle was confirmed. For an example of lancet application for diabetics, one of the needles was inserted into a human skin, and bleeding was confirmed. 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.     

Low‐temperature direct bonding of poly(methyl methacrylate) for polymer microchips

A low‐temperature, direct bonding method for poly(methyl methacrylate) (PMMA) plates has been developed by employing surface treatment by atmospheric pressure oxygen plasma, vacuum oxygen plasma, ultraviolet (UV)/ozone or vacuum ultraviolet (VUV)/ozone. Reasonable bonding strength, as evaluated by a tensile test, was achieved below the glass transition temperature (T_g). The highest bonding strength among the achieved results is 1.43 MPa (about three times the value for conventional direct bonding) at an annealing temperature of 50 °C and an applied pressure of 2.5 MPa for 10 min. Low‐temperature bonding prevents deformation of the PMMA microstructure. A prototype PMMA microchip that has fine channels of 5 µm depth was fabricated by hot‐embossing using a Si mold. After atmospheric pressure oxygen plasma activation, direct bonding was carried out at an annealing temperature of 75 °C and an applied pressure of 3 MPa for 3 min. The method gives good bonding characteristics without deformation and leakage. This low‐temperature bonding technology can be applied to polymer micro/nano structures. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Low cross talk design and simple fabrication process of electrostatic vertical comb‐drive actuators for positioning application

In this paper, different types of vertical electrostatic comb‐drive actuators are proposed. The aim of design is to minimize the cross talk between vertical and lateral motions with a relatively simple fabrication process, namely, with only two ICP‐RIE steps from the front side with layered masks. Three designs are analyzed by MEMCAD, a finite‐element modeling package, combined with a micromachining process simulator. After optimization based on the calculation, all types were fabricated and tested. The experimental results are qualitatively in good agreement with the calculations. Because of the excess undercutting in our ICP‐RIE machine, the supports were softer than designed. The displacement was larger than expected. According to obtained results, we can expect to generate a vertical force of 0.5 µN per tooth at around 50 V. The measured cross talk between vertical motion and the horizontal motion was 20%. The resonant frequency of a typical device is 9 kHz and the displacement is 1.5 µm at 50 V. 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.     

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.     

Noncontact measurement of deep tissue absorption coefficient using Spatially Resolved Near‐Infrared Spectroscopy

We examined the influence of probe‐tissue distance on the relationship between the deep tissue absorption coefficient and the spatial profile of light intensity by Monte Carlo simulation and in vivo experiments, using noncontact spatially resolved near‐infrared spectroscopy (SRS). These results suggest that noncontact SRS can be reliably used for noncontact measurement of the absorption coefficient and oxygen saturation of deep tissues. © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Process variation compensation technique for voltage‐controlled ring oscillator

A voltage‐controlled ring oscillator with process variation compensation circuits is designed using 0.25 µm CMOS technology. The simulation results show that the proposed ring oscillator increases the guaranteed frequency tuning range by 12% compared to a conventional ring oscillator. Copyright © 2007 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.     

Recent technologies of joints for HV and EHV XLPE cables in Japan

In Japan, XLPE cables are widely used for transmission lines and it is estimated that the ratio of XLPE will increase even more. The Investigation Committee of The Institute of Electrical Engineers of Japan (IEEJ), consisting of engineers from universities, all power utilities, all the major cable manufacturers, etc., has investigated the trend of the accessories (joint and termination) for XLPE cables of 66 kV and above in Japan for 3 years. This paper reports the results of this investigation. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Fast calculation method for fine‐tuned design of need‐based collateralized debt obligation (CDO)

In this paper we propose a speed‐up method for need‐based collateralized debt obligation (CDO) that meets the investor needs of the attributes of the CDO. We note the fact that the computing time to derive the best portfolio is proportional to the number of generated contract conditions that constitute the portfolio. Our method reduces the number of portfolios that can never be the best portfolios by skipping the generation of redundant contract conditions of Super Senior (SS) debt and Equity debt, which is the main cause for the increase of the generated contract conditions. A comparative experiment indicates that the proposed method makes it possible to double the types of tranches or to raise the calculation accuracy nearly 6‐fold, keeping the urgency of the calculation. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Electron‐beam‐pumped light sources using graphite nanoneedle field emitters and Si electron‐transparent films

Sputter‐induced carbon nanoneedle field emitters and Si electron‐transparent films have been developed for electron‐beam‐pumped light sources. The sputter‐induced carbon nanoneedle field emitters exhibited a stable electron emission of 0.1 mA at an average field of 13 V/µm. The 1.5‐µm thick Si electron‐transparent films achieved an electron transmittance of about 60% at an acceleration voltage of 27 kV. An electron‐beam‐pumped light source was demonstrated from the excitation of N₂ gas, and a N₂ gas spectrum was clearly observed. The increase of the beam current is important for increasing the light intensity. 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.     

Improved 3 × 3 sequential Euclidean distance transform

We propose an improved 3 × 3 sequential Euclidean distance transform (DT) using quad‐scan propagation. Our method has a separable scan structure that can be processed with a multicore processor to reduce computation time with a better accuracy. The computer simulation shows that the proposed DT algorithm approximates the Euclidean map more precisely than conventional 3 × 3 DTs while reducing dramatically computation time comparable to 8‐point sequential Euclidean distance algorithm. © 2013 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.     

Visualization of electromagnetic waves emitted from partial discharge using the constrained interpolation profile (CIP) method

The constrained interpolation profile method (CIP) is used in order to visualize the electromagnetic (EM) waves emitted from partial discharge (PD) for understanding the physical mechanisms. In this paper, the PD current is numerically obtained by the total amount of charge and the rise time. Numerical results show that the CIP is useful for visualizing the generation and the propagation of the EM waves emitted form the PD current. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.