Sohei Matsumoto

Development of bi-directional valve-less micropump for liquid

A micropump based on a novel flow rectification principle was developed. Instead of mechanical check valves, the difference of flow resistance in narrow channels caused by the temperature dependence of liquid viscosity is utilized as the basis of the valve effect. This method allows a flexible control of the pump function, including bi-directional pumping. A prototype device actuated by a piezoelectric element was designed and fabricated to confirm the pump function. The fluidic and thermal conditions for the pump actuation, and the characteristics of its behavior revealed by experiments are discussed.

Design and Fabrication of 1D and 2D Micro Scanners Actuated by Double Layered Lead Zirconate Titanate (PZT) Bimorph Beams

Micro scanners including 1D scanner beams and 2D scanning micromirrors are designed and fabricated. In order to yield large bending force, the sol-gel derived double layered lead zirconate titanate (PZT) structures are developed to be the actuator components. In our developed fabrication process, the use of thermal treatment and the addition of one platinium/titanium film played an important role to yield the well-crystallized perovskite phase and decrease the residual strss of total cantilever structures successfully. In the case of 1D scanner beams with the size of 750×230 µm2, the optical scanning angle was 41.2 deg with respect to actuation with AC 5 V at 2706 Hz. Under the applied bias of 10 V, the bimorph beam bended upward and the deflection angle of 34.3 deg was measured. A 2D scanning micromirror supported by four suspended double layered PZT actuators was designed to rotate around two orthogonal axes by the operation at different resonant frequencies. While resonating with AC 7.5 V at 3750 Hz and 5350 Hz, the maximum scanning area of 24°×26° was obtained.

2D micro scanner actuated by sol-gel derived double layered PZT

2D micro scanners actuated by sol-gel derived double layered PZT actuators were designed and fabricated. In our previous work, the better scanning capability of double layered PZT structures has been investigated. The purpose of this paper is to determine 1D and 2D scanning characteristics of 2D micro scanners with respect to resonant actuations. While resonating with 7.5 V at 3750 Hz and 5350 Hz, the scanning angle of 26/spl plusmn/2 degrees and 24/spl plusmn/2 degrees were obtained. Furthermore, the new fabrication process greatly improved the residual stress of suspended structures due to the compensation effect of double layered PZT. Wet etching process for PZT not only amended the uniformity, but also increased the device yield economically.

Three-dimensional photolithography technology for a fiber substrate using a microfabricated exposure module

This paper proposes a new three-dimensional (3D) photolithography technology for a high-resolution micropatterning process on a fiber substrate. A brief review on the lithography technology of the non-planar surface is also presented. The proposed technology mainly comprises the microfabrication of the 3D exposure module and the spray deposition of thin resist films on the fiber. The 3D exposure module is successfully prepared by the wet etching of a quartz substrate and the projection exposure method. The chief advantages of the 3D exposure module are long service life, low cost, narrow print gap and thus high resolution. A novel spray coating system has been developed for the preparation of uniform and thin resist films on the fibers, which are necessary for the high-resolution micropatterning process. The spray deposition process on the 125 µm in-diameter optical fiber has been systematically investigated. The viscosity and volatility of the resist solutions have complicated effects because the spray-coating deposition process on the fiber mainly consisted of the impinging region. The uniform and thin resist film down to 1 µm thick had been successfully achieved. Fine patterns with the line width down to 6 µm were successfully formed on the optical fiber by using the microfabricated exposure module. Preliminary photolithography experiments confirmed that the new 3D photolithography technology is one attractive low-cost solution to the integration of micro transducers onto the fibers for various applications. The 3D exposure module could also enable the continuous photolithography process on the fibers.

Development of Three-Dimensional Microstages Using Inclined Deep-Reactive Ion Etching

Three-dimensional (3-D) microstages driven by electrostatic comb actuators that provide continuous motion along three axes (x,y , and z ) were designed and fabricated. Each 3-D microstage consisted of sets of traveling tables, suspension systems, and comb actuators. To convert lateral displacement of the comb actuators to vertical motion, one suspension system incorporated leaf springs inclined to a substrate. To efficiently construct the inclined leaf springs, we devised a fabrication technique that uses deep reactive ion etching. Three-dimensional microstages were then fabricated in a 20-mum-thick device layer on a silicon-on-insulator wafer. The maximum vertical (z) displacement of this 3-D microstage was 2.6 mum, and the maximum lateral displacement (x and y) was more than 6 mum in each direction, achieved by using support suspensions to suppress the interference between the comb actuators. A 3-D microstage was then installed in a commercial atomic force microscope, and a 3-D image of a grating was successfully measured without hysteresis using this 3-D microstage as the scanning device.

Self-excited coupled-microcantilevers for mass sensing

This paper reports ultrasensitive mass detection based on the relative change in the amplitude ratio of the first mode oscillation using self-excited coupled microcantilevers. The method proposed and demonstrated using the macrocantilevers in the previous study can measure eigenstate shifts caused by objects with high accuracy without being affected by the viscous damping effect of measurement environments. In this study, moving towards the use of this method for small mass measurements, we established the self-excited coupled microcantilevers and we have achieved in measurements of very small mass (about 1 ng) with 1% order of error.

Parallelization of Catalytic Packed-Bed Microchannels with Pressure-Drop Microstructures for Gas--Liquid Multiphase Reactions

High-throughput and stable treatments are required to achieve the practical production of chemicals with microreactors. However, the flow maldistribution to the paralleled microchannels has been a critical problem in achieving the productive use of multichannel microreactors for multiphase flow conditions. In this study, we newly designed and fabricated a glass four-channel catalytic packed-bed microreactor for the scale-up of gas–liquid multiphase chemical reactions. We embedded microstructures generating high pressure losses at the upstream side of each packed bed, and experimentally confirmed the efficacy of the microstructures in decreasing the maldistribution of the gas–liquid flow to the parallel microchannels.

Two-dimensional microscanner actuated by PZT thin film

This paper introduces the fabrication and characterization of 2D resonant microscanners actuated by sol-gel deposited PZT thin films. The piezoelectric PZT thin films with silicon micromachining technology provide the advantages of high scanning frequencies and low driving voltages. The actuation principle is based on the bimorph beam structure, which consists of an oxide layer and a piezoelectric PZT layer. The 2D scanning performance can be achieved by applying AC voltages with phase shifts at resonance frequencies to the actuating beams. The devices were fabricated through thin film depositions, lithography, dry plasma etching and ICP releasing process. The fabrication processes were improved considerably. A STS ICP system was used instead of KOH or other wet-chemical etching processes to prevent the damages of front side devices while the sample was etched through. For a scanner structure with a 300 X 300 micrometers 2 mirror plate, the first four resonance frequencies were measured to be in the range of 10-30 kHz. To investigate the vibration modes, the deflections on different locations of the mirror plate were measured. The 2D scanning angles were determined to be 8 degrees at 16.2 kHz in one direction and 11 degrees at 23.4 kHz in the perpendicular direction.

A Diffuse-Interface Tracking Method for the Numerical Simulation of Motions of a Two-Phase Fluid on a Solid Surface

Applicability of two kinds of computational-fluid-dynamics method adopting Cahn-Hilliard (CH) and Allen-Cahn (AC)-type diffuse-interface advection equations based on a phase-field model (PFM) is examined to simulation of motions of microscopic incompressible two-phase fluid on solid surface. A capillarity-driven gas-liquid motion in rectangular channel is simulated by use of a PFM method for solving Navier-Stokes (NS) equations and a CH equation, whereas an immiscible liquid-liquid flow in a microchannel with T-junction and square cross section is simulated by use of another PFM method proposed in this study, which adopts a lattice-Boltzmann method based on fictitious particles kinematics as numerical scheme for solving NS equations and an AC equation that is modified to improve volume-of-fluid conservation. The major findings are as follows: (1) effect of capillary force on the dynamic two-phase fluid system with a high density ratio is well predicted for cross-sectional aspect ratio of the channel = 1 a...

MEMS-based exposure module for continuous lithography process on fiber substrates

This paper presents novel exposure module-based patterning technique for realizing continuous lithography process on fiber substrates. Fine patterns (better than 10 µm L/S) were successfully formed on the fiber with the diameter of 125 µm by using the exposure module. The exposure module exhibited advantages of low cost, easy alignment, high productivity and excellent compatibility with other microfabrication processes. It is an attractive patterning solution to the integration of functional devices and structures onto the fiber substrates.