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.     

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.     

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.     

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.     

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.     

Multijunction thermal converter with improved frequency characteristics between 10 Hz and 1 MHz

A new multijunction thermal converter (MJTC) for precision AC–DC transfer standard has been developed. A U‐shaped heater pattern was sputter‐deposited onto an AlN plate in order to reduce thermoelectric effect, which causes the frequency‐independent AC–DC transfer difference. Both low‐frequency and high‐frequency characteristics improved as a result of the new configuration, and the AC–DC transfer difference of the MJTC was evaluated to be <1 µV/V between 10 Hz and 100 kHz and <10 µV/V up to 1 MHz. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

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.     

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.     

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.     

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.     

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.     

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.     

Development of a thermal voltage converter with calculable high‐frequency characteristics

A thermal‐voltage converter for high‐frequency (HF‐TVC) AC–DC transfer standard has been developed. The HF‐TVC was designed such that the frequency characteristic is calculable from the shape and dimension of the input circuit. A new multi‐junction thermal converter element (JSTC04) has been developed, which has a simple and straight heater configuration to minimize the parasitic impedances in the input circuit. The AC–DC difference of the HF‐TVC was evaluated by two independent methods, with agreement better than 7 µV/V up to 1 MHz. © 2011 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.     

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.     

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.     

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.     

CMOS high‐precision loser‐take‐all circuit

This paper presents a new current‐mode CMOS loser‐take‐all circuit. The proposed circuit consists of a basic cell that allows implementation of a multi‐input configuration by repeating the cell for each additional input. A high‐speed feedback structure is employed to determine the minimum current among the applied inputs. The significant feature of the circuit is its high accuracy and high‐speed operation. Additionally, the input dynamic range of the circuit can be efficiently controlled via the biasing current. HSPICE simulation results are presented to verify the performance of the circuit, where under a supply voltage of 2.5 V, bias current of 100 µA, and frequency of 10 MHz, the input dynamic range increases within 0–100 µA and the corresponding error remains as low as 0.4%. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Evaluation of changes in power wheelchair maneuver induced by a downhill turning prevention control on cross sloped surfaces

In order to improve direction stability of a power wheelchair on a cross‐sloped surface, a downhill turning prevention control (DTPC) has been developed by some researchers and wheelchair suppliers. The DTPC‐induced effect on wheelchair maneuver, however, has not been well clarified. In this study, we quantitatively assessed DTPC‐induced changes in joystick control strategies during a driving task on a cross‐sloped test course. Among several evaluation measures calculated from the joystick inputs during the test trials, the x‐axis joystick displacement amount was found to be significantly decreased by the DTPC. This result suggests that the DTPC can save wheelchair users from the burden of compensation control on cross‐sloped surfaces. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A 5‐MHz AT‐cut quartz crystal oscillating circuit functioning in 350 nA

An oscillating circuit functioning at ultra low power (350 nA) for a 5‐MHz AT‐cut quartz crystal oscillator was investigated. This circuit has a resistance between the power terminal of the CMOS‐IC and the power supply, and another between the earth terminal of the CMOS‐IC and the ground (GND). These resistances discourage an inrush of current, and set a gain (g_m) necessary for oscillating the circuit at minimum. The developed circuit is quite simple, but enables driving at once‐unthinkable, low power (below 1 µA). © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.