• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1824-1827
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• 2005

For application to micro fluid control systems such as ${\mu}TAS$ (Micro Total Analysis Systems) and DDS (Drug Delivery Systems), it is very significant to handle precise and minute flow rates with low pressure pulsation. In this study, a novel valveless piezoelectric pump using peristaltic motion with three disk type PZT actuators is presented. The newly devised pump with an effective size of $70mm{\times}60mm{\times}55mm$ has three actuator layers connected in series from inlet to outlet. The PZT actuator has a maximum displacement of 240 ${\mu}m$ and a maximum force of 1.6 N. When the driving voltage for PZT actuators is sequentially applied with a certain phase shift, the pumping is performed by peristaltic motion of liquid volume. The working fluid is shut off without the driving voltage. Three methods for sequential driving are proposed and experimentally investigated. First and second methods utilize an intermittent sinusoidal waveform with phase shift of $90{\circ}\;and\;120^{\circ}$, respectively. Third method uses a rectangular waveform with phase shift of $90^{\circ}$. A controller with multi-phase shifter is designed and fabricated. Then, frequency and voltage-flow rate characteristics and load pressure-flow rate characteristics are experimentally investigated to verify the validity of the developed pump.

• JSTS:Journal of Semiconductor Technology and Science
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• v.2 no.4
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• pp.259-267
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• 2002

We present a novel 3D fabrication method with single X-ray process utilizing an X-ray mask in which a micro-actuator is integrated. An X-ray absorber is electroplated on the shuttle mass driven by the integrated micro-actuator during deep X-ray exposures. 3D microstructures are revealed by development kinetics and modulated in-depth dose distribution in resist, usually PMMA. Fabrication of X-ray masks with integrated electrothermal xy-stage and electrostatic actuator is presented along with discussions on PMMA development characteristics. Both devices use $20-\mu\textrm{m}$-thick overhanging single crystal Si as a structural material and fabricated using deep reactive ion etching of silicon-on-insulator wafer, phosphorous diffusion, gold electroplating, and bulk micromachining process. In electrostatic devices, $10-\mu\textrm{m}-thick$ gold absorber on $1mm{\times}1mm$ Si shuttle mass is supported by $10-\mu\textrm{m}-wide$, 1-mm-long suspension beams and oscillated by comb electrodes during X-ray exposures. In electrothermal devices, gold absorber on 1.42 mm diameter shuttle mass is oscillated in x and y directions sequentially by thermal expansion caused by joule heating of the corresponding bent beam actuators. The fundamental frequency and amplitude of the electrostatic devices are around 3.6 kHz and $20\mu\textrm{m}$, respectively, for a dc bias of 100 V and an ac bias of 20 VP-P (peak-peak). Displacements in x and y directions of the electrothermal devices are both around $20{\;}\mu\textrm{m}$at 742 mW input power. S-shaped and conical shaped PMMA microstructures are demonstrated through X-ray experiments with the fabricated devices.

• Advances in nano research
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• v.9 no.3
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• pp.133-145
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• 2020

In this study, nonlinear vibrations and dynamic instabilities of a smart embedded micro shell conveying varied fluid flow and subjected to the combined electro-thermo-mechanical loadings are investigated. With the aim of designing new hydraulic sensors and actuators, the piezoelectric materials are employed for the body and the effects of applying electric field on the stability of the system as well as the induced voltage due to the dynamic behavior of the system are studied. The nonlocal piezoelasticity theory and the nonlinear cylindrical shell model in conjunction with the energy approach are utilized to mathematically modeling of the structure. The fluid flow is assumed to be isentropic, incompressible and fully develop, and for more generality of the problem both steady and time dependent flow regimes are considered. The mathematical modeling of fluid flow is also carried out based on a scalar potential function, time mean Navier-Stokes equations and the theory of slip boundary condition. Employing the modified Lagrange equations for open systems, the nonlinear coupled governing equations of motion are achieved and solved via the state space problem; forth order numerical integration and Bolotin's method. In the numerical results, a comprehensive discussion is made on the dynamical instabilities of the system (such as divergence, flutter and parametric resonance). We found that applying positive electric potential field will improve the stability of the system as an actuator or vibration amplitude controller in the micro electro mechanical systems.

• Journal of Powder Materials
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• v.15 no.1
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• pp.46-52
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• 2008

The restrictor, which is a fluid channel from a reservoir to a chamber inside a thermal micro actuator, has been fabricated using ArF and KrF excimer lasers, Diode-Pumped Solid State Lasers (DPSSL) and femtosecond lasers for a feasibility study. A numerical model of fluid dynamics for the actuator chamber and restrictor is presented. The model includes bubble formation and growth, droplet ejection through nozzle, and dynamics of fluid refill through the restrictor from a reservoir. Since an optimized and well-fabricated restrictor is important for a high frequency actuator, some special beam delivery setups and post processing techniques have been researched and developed. The effects of variations of the restrictor length, diameter, and tapered shapes are simulated and the results are analyzed to determine the optimal design. The numerical results of droplet velocity and volume are compared with the experimental results of a cylindrical-shaped actuator. It is found that the micro actuators having tapered restrictors show better high frequency characteristics than those having a cylindrical shape without any notable decrease of droplet volume. The laser-fabricated restrictors demonstrate initial feasibility for the laser direct ablation technique although more development is required.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.4
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• pp.161-167
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• 2002

For the purpose of applying to micro-actuator, thermal properties and displacement of electrostrictive polyurethane(PU) elastomers have been measured. In order to understand an effect of PU component, crosslinking agent are controlled by 0.5 wt% and 1 wt%. DMPA and anther chain extenders were used. PU sample that chain extenders are DMPA is added NaOH for comprehension of effect of ionic groups. The deposited electrode sire on PU films is equal to acrylic holder size when the displacement was measured. Dynamic response according to frequency, displacement and recovery time according to PU thickness were measured. 1 wt% crosslinking agent contents PU samples have higher displacement and lower recovery time than 0.5 wt% crosslinking agent contents PU. If the PU thickness is increased, the actuating voltage for generating of same displacement is increased, too.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.131-132
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• 2006

This paper presents a micro-positioning platform based on the unique parallel mechanism recently developed by the authors. The platform has a meso-scale rectangular shape whose size is $20{\times}23m$. The stroke is 5 mm for both the x- and y-axis and 100 degrees for the ${\alpha}$-axis(the rotational axis along the x-axis). The platform is actuated by the three sets of two-stage linear actuators: a linear motor for rough positioning and a piezo actuator for fine positioning. The platform is already assembled. Experimental results of the positioning measurements and control performance are presented.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.528-531
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• 2000

Deposition of PZT with UV laser ablatio was applied for realization of thin film sensors and actuators. Deposition rate of more than 20nm/min was attained by pulsed KrF excimer laser deposition, which is fairly better than those obtained by the other methods. Perovskite phase was obtained at room temperature deposition with Fast Atom Beam(FAB) treatment and annealing. Smart MEMS(Micro electro-mechanical system) is now a suject of interest in the field of micro optical devices, micro pumps, AFM cantilever devices etc. It can be fabricated by deposition of PZT thin films and micromachining. PZT films of more than 1 micron thickness is difficult to obtain by conventional methods. This is the reason why we applied excimer laser ablation for thin film deposition. The remanent polarization Pr of 700nm PZT thin film was measured, and the relative dielectric constant was determined to about 900 and the dielectric loss tangent was also measured to be about 0.04. XRD analysis shows that, after annealing at 650 degrees C in 1 hour, the perovskite structure would be formed with some amount of pyrochlore phase, as is the case of the annealing at 750 degrees C in 1 hour.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.3 s.96
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• pp.72-77
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• 1999

This paper presents 2-dimensional vibration cutting increases dynamic stiffness of tool support and improves the quality of machined surface in micro-machining. 2-dimensional vibration cutting is generated by two piezo actuators arranged orthogonally. A sine-type voltage is input to one actuator and a phase-shifted sine-type voltage is input the other. Then the vibration device actuates the tool in a 2-D elliptical motion with pulsed cutting force. It is a characteristic of 2-D vibration cutting that some negative thrust force occurs as the direction of friction on a tool rake surface is reversed. It helps not only chip flow smoothly and continuously but also cutting force be reduced. The quality of machined surface by 2-D vibration cutting depends on such parameters as vibration amplitude, frequency, cutting speed, depth of cut, etc. Compared to conventional cutting through tool path simulation and experiments under several conditions, the 2-D vibration cutting is verified to bring forth a great decrease of cutting forces, much better surface roughness and moreover much less burr.

• Composites Research
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• v.22 no.6
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• pp.7-12
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• 2009

This paper deals with a fabrication method of composite hinge mechanisms for flapping-wing micro air vehicles. The fabrication process includes curing process of Graphite/Epoxyprepregs, laser cutting for high fabrication repeatability, laminating of Graphite/Epoxy prepregs with Kapton film which is used for flexure, and so on. The fabricated hinge mechanism was attached with PUMPS actuators and the measured flapping angle was $173^{\circ}$ when driving voltage was 300V 170Hz.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.9
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• pp.5758-5762
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• 2014

Electrostatically-actuated Micro device have been used widely in a variety of integrated sensors and actuators. Electrostatically-actuated micro devices with a gap of several micrometers or less between the electrodes have shown failure problems by electrostatic adhesion. To improve this adhesion phenomenon, micro devices of varying lengths and widths in electrodes were fabricated, and an alumina coating was then deposited using atomic layer deposition technology. The effects of improving adhesion phenomenon were compared by measuring the pull-in voltage before and after the coating process. The pull-in voltage increased with increasing length of the upper electrode after the coating. An increase in the electrode area results in an increase in the pull-in voltage after coating. The alumina coating method applied to improve the adhesion on an electrostatically-actuated micro device was observed as an effective method.