神田 健介

This paper shows the fabrication of the prototype of electromagnetic MEMS energy harvester and the power generation experiment al results. The electromagnetic energy harvester consists of the sputtered NdFeB magnet film on high aspect ratio corrugated Si trench and the Au serpentine coil. The each structure of the device is fabricated with the optimum geometry designed by the FEM simulation. In the result, we obtained 2.65 mV of the induced electromotive force and 7.60 nW of the output power. The experimental results agreed well with simulation results, and we confirmed the usefulness of the analytical method for the estimation of the power generation.

エレクトレットを用いた静電型エナジーハーベスタは,振動マスにエレクトレットを成膜・荷電し対向電極との静電誘導で発電するデバイスである.そのため,発電電力や電力が最大になる最適負荷はマスの振動周波数や振幅によって大きく変化する.電気回路シミュレータ(SPICE)では可変容量のモデルを作成することで,時間変化に対する電極間の容量変化を表すことができる.そこで,本研究では有限要素法を用いてフリンジ効果を考慮した電極間の静電容量を解析し,その結果を等価回路モデルに利用することで,SPICEシミュレータ上でマスの動きに対するハーベスタの発電波形や最適負荷を解析した.その結果と実デバイスとの比較を行うことで,SPICEの等価回路モデルが発電量や最適負荷の見積もりに有用であることを確認した.

We studied the effect of hydrophobic microstructural shape on laminar drag reduction experimentally. Deep truncated cone holes are machined into a test wall surface, and the surface is coated with triazine thiol to induce hydrophobicity. The aperture ratios of the test walls are 10% and 20%. Drag reduction was estimated by measuring the pressure loss in microchannels. The Reynolds number range for drag reduction in the case of the test walls was found to be wider than that in the case of conventional walls. Additionally, the percentage of drag reduction for test walls is comparable to that for conventional walls with smaller aperture ratios.

In this study, we report the optimization of electrode design for increasing output power of the vibration electrostatic energy harvesters. The output power depends on the capacitance change and its frequency. Without consideration for fringe effect of a parallel-plate capacitance, the narrower electrode pitch L is, the larger output power. However, under actual conditions, power output is limited by fringe effect. To consider fringe effect, the optimum electrode dimension changes due to the distance between the electret and counter electrode. By using FEM analysis with fringe effect, we find the characteristic of fringe effect at parallel-plate capacitor, and then the optimum width of counter electrode fFand electrode pitch L are obtained.

This paper shows the optimization of the structure of the electromagnetic energy harvester consisting of the sputtered NdFeB film on high aspect ratio Si trench and the Au serpentine coil. The magnetic flux density change is caused by distance change between coil and magnet film on the corrugated Si. In order to maximize the harvesting energy, the optimum parameters such as width, depth of Si trench, and coil size are investigated by FEM analysis and theoretical calculation. Assuming the trench depth of 400 μm the vibration amplitude of 400 μm_<p-p> and the frequency of 100 Hz the maximum output power of 12 nW and the maximum electromotive force of 4 mV are obtained by 60 μm and 80 μm, respectively.

Continuous human monitoring is substantially useful to realize a high QoL (quality of life) society. In the previous work, we fabricated a prototype system for monitoring an electrocardiograph (ECG), heart rate (HR), 3 axes human body acceleration, temperature for human body and human circumstances, simultaneously. These data are transmitted to the host PC and used for analyzing the human activities and conditions such as a heart rate variability (HRV). The HRV that calculated from HR is valuable for recognizing a mental or physical stress of human subjects. In this study, we demonstrate a fuzzy logic HR extraction algorithm on the prototype system to realize an autonomous HRV monitoring system. On-board fuzzy algorithm will reduce the communication traffic and improve an accuracy of the HR extraction. From the implementation result, the error ratio of the HR extraction is improved from 0.9 % to 0.4 %. © 2012 TSI Press.

In this paper, we presented a measurement of power output versus acceleration with a data logger. The vibration energy harvester consists of a Si grid, a vibration mass, which has a charged electret film, and a cover glass. The data logger can measure voltage outputs, acceleration, temperature, humidity, and electrocardiogram (ECG). Accelerations and output voltages from the harvester were measured by 10 bit ADC (analog-to-digital converter) and the sampling frequency was 125 Hz. The power output at different accelerations on modal thruster is calculated by the output voltage from the harvester and the 20 MΩ load resistance. The power output was proportional to acceleration and the maximum generated power was 17.3 nW. The generated power worn on ankle while walking was 2.1 nW.

In this study, an electret based energy harvester with a single silicon structure that shares harvesting counter electrodes and charging grid is demonstrated. The shared electrode achieves the batch fabrication process that can avoid the charge leakage from the charged electret. The mass structure supported by the thin Si spring has resonant frequency of 40Hz. The harvesting demonstration showed the 0.23μW at 10Hz, 0.1G with load resistance of 1MΩ.

There has been an increase of research into μTAS. In general, detection with this device is based on a reaction between reactants in the fluid and on the wall of a microchannel. Therefore, it is important to elucidate physical phenomena in the near-wall region of the microchannel to achieve design optimization of the device. The aim of this study is experimental elucidation of single-nanoparticle behavior in microfiuid by observation with an evanescent illumination which allows three-dimensional location measurement of nanoparticles in the near-wall region. Instead of biological molecules, fluorescent nanoparticles (20 nm diameter) were employed for the single particle imaging. Since there are issues of a measurement accuracy due to considerably small diameter of nanoparticles for the imaging and low brightness of a single nanoparticle in the deeper location, an optimal setting of shooting and a novel algorithm of image processing were proposed. The result of experiments showed that perpendicular distribution of nanoparticle concentration exists.

Micro biochemical analysis chip have attracted attention for merits such as speed up and high efficiency of analysis. For detection, we often use immune reaction such as antibody-antigen reaction which occurs near the wall. Therefore, the concentration distribution of biomaterials near wall greatly affects detection and reaction. In this study, we attempted to evaluate interaction between the nanoparticles and the wall and to control particles for the aim of advancement of reaction efficiency. First, we measured the concentration distribution of particles 100 nm in diameter by using TERFM which expose evanescent light which intensity decay exponentially. Using this characteristic, we identified particle's 3D-position from luminance of particle. The result shows that concentration of particles drastically increases with increasing distance from the wall. Subsequently, we tried to gather particles to the wall by applying electric field to suspension. The result shows that particles moved and attached to the wall.

A novel concept of a liquid transport technique utilizing frequency modulation and local resonance oscillation is proposed and it is applied to a micromixer. Meta-structure distributing local masses for generating local resonant oscillation is developed. Vibration of the meta-structure with sweeping frequency produces changes in the positions with large oscillation amplitude. This complex structural oscillation makes eddy-like disturbance of flow in a microchamber, and it produces high mixing efficiency. Using this technique produced a mixing index of 0.92 with the volumetric flowrate of 1 μL/min, while it was 0.49 for a conventional technique employing a vibration at a fixed frequency.

The Particle motion at near-surface is greatly important for efficiency in micro chip. In this paper, concentration distribution of polyethylene latex particle (diameter 100 nm) at near-surface in micro-channel is evaluated by total internal reflection fluorescence microscopy. And particle-wall interaction forces (van der Waals, electrostatic, and lift force) are investigated. The results show the concentration is the largest at specific location from the wall surface. The location is consistent with balance position of theoretical particle-wall interaction force in static fluid. In flow field, the largest value location is far away from wall as increasing velocity. This impact is lower with high-ionic strength.

A novel concept of micromixer proposed in this study provides complex perturbation in a micromixer chamber. The chamber wall has meta-structure, which has multiple local masses on the chamber wall. Oscillation is applied to the metastructure with modulating frequency, resulting on local resonance oscillation. Measured amplitude mapping of the vibration corresponded to harmonic responses obtained from finite-element-analyses. This complex structural oscillation produces high mixing efficiency. Using this technique produced a mixing index of 0.92 with the volumetric flowrate of 1 μL/min, while it was 0.49 for a conventional technique.

The velocity profile of a dilute polymer solution and a surfactant solution near the wall surface in a microchannel was clarified using evanescent wave illumination and a particle tracking velocimetry system. Fluorescent particles with a diameter of 100 nm were used as tracer particles. The test fluids were polyethylene-oxide (Peo15) solution at 5 ppm, oleyl-bihydroxyethyl methyl ammonium chloride (Ethoquad 0/12) solution at 200 ppm and distilled water. The results obtained for the velocity profiles for distilled water and surfactant solution were found to agree well with the two-dimensional Poiseuille velocity profile. On the other hand, the velocity profile of the dilute polymer solution decreases significantly compared with that of water within 200 nm of the wall surface. These data provide the first velocity profile measurements of a dilute polymer solution and a surfactant solution in the near-wall region. Copyright © 2006 by ASME.

The velocity profile of a dilute polymer solution near the wall surface in a microchannel was clarified using evanescent wave illumination and a particle tracking velocimetry system. Fluorescent particles with a diameter of 100nm were used as tracer particles. The test fluids were polyethylene-oxide (Peo15) solutions at 5 ppm and distilled water. It was clarified that the velocity profile of the dilute polymer solution decreases significantly compared with that of water within 200nm of the wall surface. Brownian motion of the particle near the wall surface was suppressed by the polymer solution, and the suppression was emphasized under the flow condition.

This study aims at visualization of the bio-molecules dissolved in the solution near the surface using evanescent wave light. A system was developed for the visualization, which consists of total reflection fluorescent microscopy, Intensified CCD camera and PIV image processing system. Brownian motion of particle with diameter of 100nm and the concentration near the wall was evaluated. Furthermore, to evaluate the effects of the wall, surfaces with hydrophilic and hydrophobic wettability are prepared. The results show that the wall effects on the average displacement of Brownian motion and concentration profile of the particles. It is suggested that interaction between surface and particles are effective for the Brownian particles. The technique is applicable for bio-molecules analysis.

This paper describes high performance microactuator and microvalve for micropump fabricated by metal-forming process. The process has advantage of process cost, time, throughput and degree of freedom compared to SC process. Additionally, in recently years, it can manufacture micro devices (μm〜) using such as microassembly in progressive die and laser process, and effective in the area of micro fluid devices which need to be disposable because those devices treat bio-fluids. We proposed high performance microactuator and microvalve by metal-forming which be able to 3-D process. The former is of 3-D dome bi-metal which give rise to buckling. The displacement of 3mm diameter and 0.07mm thickness reached to about 570μm The later is thin metal cantilever with 3-D spring element. The structure can reduce critical pressure at which valve begins to open.

A design approach of valve-less diffuser micropump driven by piezoelectric element (PZT) was developed. Its performance is higher than previous pump, because of following two reasons. Firstly, range of applied viscosity is wide. Secondly, a flow rate is controllable widely low to high. With the result that maximum viscosity of 23mPa・s and maximum flow rate of 700μL/min were achieved. These results have high potential for the pump development to dilute high viscosity sample.

For the investigation of near surface phenomena, a novel method, which is to measure velocity profile in the direction of depth, are suggested. By changing the angle of induce light, illuminated penetration depth is changed. The velocities of fluorescent tracers are successfully measured using PTV technique. The fluid including bio-molecules is employed for velocity measurement. The velocity profile of bio-fluid is measured by eliminating the influence of the Brownian motion of tracers. The velocity profile of the flow agrees well with the plane Poiscruille flow equation except for the results at large distance from the wall. It is assumed that the difference in the velocity at the large distance results from the inhomogeneous concentration profile due to surface potential. In our knowledge, the method suggested in this study is the first one in terms of measuring flow velocity profile in direction of depth near wall surface.

To analyze near surface phenomenon such as the interaction between wall and bio-molecules, which relate to reaction efficiency for the micro total analysis system utilizing the reaction on the wall surface, concentration profile and Brownian motion of fluorescent particles as quasi-bio-molecules are experimentally evaluated. For the evaluation, combination of TIRM and PIV technique are employed. It is verified that Brownian displacement of fluorescent particle near the surface is smaller than that in bulk fluid. For concentration profile measurement, increasing concentration profile with increasing distance from the wall and increasing concentration gradient with increasing flow velocity are observed. Copyright © 2005 by the Transducer Research Foundation, Inc.

To analyze near surface phenomenon such as the interaction between wall and bio-molecules, which relate to reaction efficiency for the micro total analysis system utilizing the reaction on the wall surface, concentration profile and Brownian motion of fluorescent particles as quasi-bio-molecules are experimentally evaluated. For the evaluation, combination of TIRM and PIV technique are employed. It is verified that Brownian displacement of fluorescent particle near the surface is smaller than that in bulk fluid. For concentration profile measurement, increasing concentration profile with increasing distance from the wall and increasing concentration gradient with increasing flow velocity are observed.

The purpose of this study is to clarify the velocity profiles of dilute polymer solution near the wall surface by using an evanescent light source. Evanescent light emerges by total reflection of an incident laser and illuminates only particles that are very close to the wall surface. By changing the incident angle of the laser, the depth of the illuminated area of evanescent light can be changed. Test fluids were water and polyethylene-oxide (Peo15) solutions with 5 ppm. Fluorescent particles with the diameter of 100nm were dispersed in test fluids are used as tracer particles. The streamwise velocity profile in the direction of depth is measured with PTV system by changing the depth of the illuminated area. It was clarified that the velocity profiles of dilute polymer solution decreases significantly comparing that of water very close to the wall surface. It can be considered that the adsorbed polymer layers may be partially responsible for the decrease in velocity of polymer solution.

We focus attention on the qualitative evaluations of the bio-fluid flow in micro-channel taken surface friction force into account. Lateral force mode of SPM (Scanning Probe Microscopy) was used for measuring surface friction force with nN scale order accurately. On the other hand, conventional hydrodynamic pressure drop measurement was carried out for measuring macro flow behavior of the flow. Results of Bio-fluid flow on hydrophobic surface by pressure drop measurements show 7% reduction of pipe friction coefficient. These measurements have sufficient reliability due to accurate measurement apparatus and samples. The error of the measurement was 3.9% with 95% comprehension. We think that the 7% reduction was occurred due to surface chemical, electrical or physical interaction. These results show interactions between flow and surface molecules highly influence on macro continuum flow.

A valve-less micropump device integrated with mixer was developed. This pump can cover the shortcomings of valve-less pump, that is low performance of flow rate and maximum pressure. Resultant performance of the device is flow rate of 120μL/min, maximum pressure of 12kPa and mixing time of a few hundred msec. This performance is enough to use as a pump for mixing. The device has high potential for application of bio- and chemical micro analysis system.