• Journal of the Korean Society of Visualization
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• v.17 no.2
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• pp.90-95
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• 2019

In the present work, the effect of flow parameters such as volume flow rate on focal point of fluidic micro lens is investigated numerically. ANSYS Fluent is used for simulations, and the flow parameters and number of simulations are determined using the space filling method of design of experiment (DOE). Having determined the location of interfaces between fluids inside the micro lens which acts as the lens curvature, a ray tracking simulation on each case is performed using COMSOL Multiphysics to determine the focal point for each lens. These data are then used to provide a relation between flow parameters and the focal point of the lens.

• Journal of the Optical Society of Korea
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• v.16 no.1
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• pp.22-28
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• 2012

We report a focal-length tunable liquid lens based on thermopneumatically driven fluidic pressure. The fluidic pressure is generated by deformation of an elastomeric diaphragm induced by thermopneumaticity from a laterally integrated microheater sealed within an air chamber. The pressure is transmitted by a confined liquid to a lens diaphragm through an internal fluid channel. The liquid filling under the lens diaphragm functions as a liquid lens for dynamic focusing with properties depending on the curvature of the deformed diaphragm. The diaphragm area of the air chamber is designed five times larger than that of the lens cavity to yield high focal-length tunability by amplified deflection of the lens diaphragm. With our method, we achieved excellent focal-length tunability from infinity (without an input current) to 4 mm (with an input current of 12 mA) with a lens aperture diameter of 2 mm.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.572-575
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• 2005

A microlens connected to microfluidic channel is fabricated. The microlens is sealed with an elastomeric membrane which deforms by pressure of fluid driven by a syringe pump resulting in the shape change of the microlens. The optical properties of the microlens could be controlled by changing the microlens shape. The microlens system were made of an elastomer, PDMS, using molding from a photoplastic master patterned by UV photolithography. The test results show the optical property of the lens could be made into convex and concave type by applying the fluidic pressure positive and negative.

• Design & Manufacturing
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• v.7 no.1
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• pp.55-59
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• 2013

A Light Emitting Diode(LED) is a semiconductor device which converts electricity into light. LEDs are widely used in a field of illumination, LCD(Liquid Crystal Display) backlight, mobile signals because they have several merits, such as low power consumption, long lifetime, high brightness, fast response, environment friendly. In general, LEDs production does die bonding and wire bonding on board, and do silicon and phosphor dispensing to protect LED chip and improve brightness. Then lens molding process is performed using mixed liquid silicon rubber(LSR) by resin and hardener. A mixture of resin and hardener affect the optical characteristics of the LED lens. In this paper, computational design of static mixer was performed for mixing of liquid silicon. To evaluate characteristic of mixing efficiency, finite element model of static mixer was generated, and fluidic analysis was performed according to length of mixing element. Finally, optimal condition of length of mixing element was applied to static mixer from result of fluidic analysis.

• Journal of Sensor Science and Technology
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• v.28 no.5
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• pp.294-298
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• 2019

Pulsed laser-based optical sensor monitoring systems for real time microplastic particle counting are proposed and developed in this study. To develop our real time monitoring system, we used a 450 nm pulsed laser and a photomultiplier with very high quantum efficiency. First, we demonstrated that the microplastic particle counting system could detect standard micro bead samples of 100, 250, and $500{\mu}m$ in river water. We then performed research concerning pulsed laser-based optical spectral sensor systems for real time microplastic monitoring. Additionally, we demonstrated that the real time microplastic remote monitoring system using LoRa communications could detect microplastic in the tap water resource protection area.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.5
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• pp.557-560
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• 2010

We have designed a digital variable-focal-length liquid lens by using 4-bit actuators. Each bit actuator consists of 1, 2, 4, and 8 unit actuators, squeezes discrete fluidic volume of $2^4$ different levels into the lens The 4-bit digital actuation mode ($b_4b_3b_2b_1$) affords $2_4$ different lens curvatures and focal lengths. The on/off control of the bit actuators helps in solving the main problem associated with analog liquid lenses, i.e., precise control of the pressure or volume of the fluid for changing the lens curvature and focal length. Experimentally, it has been found that the 4-bit actuators allow 0.074 nl (${\pm}0.02\;nl$) of the given fluid per bit to enter the lens and help in increasing the focal length from 3.63 mm to 38.6 mm in $2^4$ different levels; no high-cost controllers are required for precise control of the pressure or volume in this case. Therefore, the present digital liquid lens is more suitable to integrated optical systems by reducing additional component for pressure and volume control.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.6
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• pp.636-641
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• 2009

Recently, expansion of micro-technology parts requires micro-precision machining technology. Micro-groove machining is important to fabricate micro-grating lens and many micro-parts such as microscope lens, fluidic graphite channel etc. Conventional groove fabrication methods such as etching and lithography have some problems in efficiency and surface integrity. But, mechanical micromachining methods using single crystal diamond tools can reduce these problems in chemical process. For this reason, microfabrication methods are expected to be very efficient, and widely studied. This study deals with machinability in micro-precision V-grooves machining of nickel plated layer using non-rotational single crystal diamond tool and 3-axis micro stages. Micro V-groove shape, chip formation and tool wear were investigated for the analysis of machinability of Ni plated layer.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.3 s.180
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• pp.156-162
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• 2006

Direct fabrication of nano patterns has been studied employing a nano-stereolithography (NSL) process. The needs of nano patterning techniques have been intensively increased for diverse applications for nano/micro-devices; micro-fluidic channels, micro-molds. and other novel micro-objects. For fabrication of high-aspect-ratio (HAR) patterns, a thick spin coating of SU-8 process is generally used in the conventional photolithography, however, additional processes such as pre- and post-baking processes and expansive precise photomasks are inevitably required. In this work, direct fabrication of HAR patterns with a high spatial resolution is tried employing two-photon polymerization in the NSL process. The precision and aspect ratio of patterns can be controlled using process parameters of laser power, exposure time, and numerical aperture of objective lens. It is also feasible to control the aspect ratio of patterns by truncation amounts of patterns, and a layer-by-layer piling up technique is attempted to achieve HAR patterns. Through the fabrication of several patterns using the NSL process, the possibility of effective patterning technique fer various N/MEMS applications has been demonstrated.