神田 健介

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.

For the establishment of the design methodologies of micro fluidic chips, the essential analysis of the flow behavior on the micro-meter scale and surface interactions on the nano-scale has been investigated. The understanding of bio-fluid flow behavior in the micro-systems includes both the basic fluid dynamic problems and driving forces from the fields of application. Attention has been focused on the clarification of the surface effects on the solution of bio-molecular flow at micro-scale dimensions. Investigations of pressure drop measurements in bio-molecular flow together with measurements of biomolecular absorption and the lateral forces on various surfaces were carried out on both micro and nano scale. The results demonstrated a clear correlation between flow drag and bio molecular interaction with the surface. The validity is demonstrated of the evaluation method suggested in this paper. Copyright © 2004 by ASME.

To investigate the relation between nano scopic surface interaction and whole flow behavior for the bio-fluid flow in micro tubes with various surface properties, lateral force, absorption, and pressure drop measurements were carried out. The results of pressure drop measurement showed the reduction of the friction factor dependent on surface property and the concentration of the bio-molecules. The tendency of the measured frictional force corresponds to the molecular absorption on the surface. It is concluded that the whole flow behavior relates to the surface phenomenon in micro flow of bio-fluids.

A design approach of valve-less diffuser micropump driven by piezoelectric element (PZT) was developed, with the result that a flow rate of 210 μL/min and maximum pressure of 37kPa were achieved. In addition, we showed the effect of the viscosity and the cross-section areas of before/after chamber on the PZT displacement magnitude performance. These results were utilized for the pump development to equalize the flow rate of solutions with different viscosity. The pump has high potential for application of bio-and chemical micro analysis system.

This study aims at visualization of the flow near the wall surface in microchannelusing evanescent wave on a near-field optical microscope. A system was developed for the visualization, which consists of total reflection fluorescent microscopy, Intensified CCD camera, PIV image processing system, microchannel, syringe pump. Including Brownian motion of particle with diameter of 100nm or less was evaluated. Flowanalysis near the surface of a wall was performed. The influential factors onvisualization of micro-flow were evaluated quantitatively. The flow rate near the surfacein a microchannel is measured. The validity of developed experimental system wasshown. On the other hand, using 60nm diameter fluorescent particles, flow analysis was performed. The technique is applicable for analyzing bio-fluid with bio-molecules tracer.

Bio-fluids flow in Bio-MEMS (Bio-Micro-Electrical-Mechanical-Systems) or μTAS (Micro-Total-Analytical-Systems) chips, which are recently attracted, have some problems such as deformation of bio-molecules and aggregation of bio-molecules to a wall. Such problems can cause blockage or breakage of the chips. In this work, we aim to evaluate biofluids flow on a hydrophobic surface for preventing aggregation of bio-molecules. Concretely, relation between pressure drop and volumetric flowrate was investigated. While flow in the hydrophilic micro-tubes with 100μm order for diameter agreed well with the conventional Hagen-Poiseuille equation, results for hydrophobic micro-tubes show that volumetric flowrates was larger than analytical value of those. For biofluid flow, the aggregation of bio-molecules could lessen the effects of increasing volumetric flowrates. The evaluations of aggregation on the hydrophobic surface for biofluid are now on investigating.