• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.2
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• pp.131-136
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• 2008

Using ultrasonic standing waves, micro particles submerged or flowing in fluid can be manipulated. Due to acoustic radiation force of ultrasound, particles are forced to move to pressure nodal or antinodal lines. In this work, we propose a method to control the position of micro particle in a flow by adjusting the frequency of the standing wave. To this end, standing wave field generation system including a few millimeter thick micro channel was established using an immersible ultrasonic transducer. The present generation system works valid in a frequency range between 2.0 MHz and 2.5 MHz. We observed the SiC particles in water moved to pressure nodal lines by the standing wave. The effect of the channel thickness and operating frequency was also investigated. Interestingly, it was shown that the operating frequency have a close relation with the location of the pressure nodal line. Consequently, it fan be said that the position of particle movement rail be controlled by adjusting the ultrasound frequency. The maximum range of the controllable position was about 261 micrometers under the given condition. The resulted observations reveal the possibility of various applications of the ultrasonic standing wave to the manipulation of particles submerged in a fluid.

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.16-17
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• 2003

수 십 ∼ 수 마이크로 크기의 미세 입자에 강하게 집속된 빔을 산란시키게 되면 입자들은 운동량의 변화에 따라 광의 초점부근에서 포획되는 힘을 받게 된다. 이런 힘은 scattering force와 gradient force로 구분할 수 있고, Optical tweezers는 광의 gradient force를 이용하여 미세입자를 포획하고 조작하는 기술이다. 광에 의해 물리적인 접촉 없이 입자를 포획할 수 있다는 사실로부터 optical tweezers는 생물학을 비롯한 많은 분야에서 유용한 도구로 사용되어지고 있다. (중략)

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2001.11a
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• pp.431-432
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• 2001

원심력을 이용한 대표적인 대기오염 방지 장치인 싸이클론은 1800년대 후반이래 공기나 배출가스로부터의 분진제거 및 입자분리에 폭 넓게 사용되어 왔다. 일반적으로 싸이클론은 간단한 구조로 되어 있으며, 조작이 용이하고 운전비용이 저렴할 뿐만 아니라 가혹조건에서의 사용이 가능하다는 장점이 있다 (Shepherd and Lapple, 1939). 입자의 관성력에 의해 분진을 분리하는 싸이클론으로서는 상대적으로 낮은 관성효과를 지니는 미세입자(주로 10$\mu\textrm{m}$ 이하)들에 대한 제어효율이 낮을 수 밖에 없다(Dirge and Leith, 1985). (중략)

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.228-229
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• 2000

1970년 Ashkin이 레이저 광압을 이용하여 수 마이크로미터 크기(micrometer sized)의 유전체를 광속의 진행 방향으로 가속시킴과 동시에 광속축(beam axis)방향으로 입자를 끌어당기는데 성공함으로써 레이저를 이용한 미세구(micro-particle) 의 포획 및 조작에 대한 연구와 실험이 시작되었다$^{[1]}$ . 이후에 많은 사람들에 의해 연구가 활발히 이루어졌으며$^{[2]~[7]}$ , 이러한 레이저를 이용한 미세구의 포획방법은 광집게(optical tweezer)로써 생물학과 물리학 분야에서의 높은 가능성 때문에 지금도 연구가 계속되고 있다. (중략)

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.4 no.1
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• pp.59-64
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• 2006

Ion exchange resin particles should not be found in steam generator(S/G) sludge. The suspicious spherical resin particles observed in S/G sludge sample were characterized for particle size distribution under optical microscope using the micro-technique, for element analysis by the electron probe micro analysis (EPMA), and for molecular identification by the IR spectroscopy. The particle sizes are distributed from 1 to $200{\mu}m$ for the sludge, while 40 to $500{\mu}m$ for the spherical resin particles. The results of the elemental analysis showed different major impurities: Si, Al, Mn, Cr, Ni, Zn and Ti for the sludge particles, while Si, Cu, Zn for the spherical resin particles. However, both particles contain Fe as a matrix of magnetite $(Fe_3O_4)$. IR spectrum of the spherical particles was not quite similar to the IR spectrum of ion exchange resins used in S/G system. These results indicate that the spherical particles are not related to ion exchange resin particles and may be formed by the process of the sludge formation.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.06a
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• pp.129-136
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• 2005

There should not be ion exchange resin particles in S/G sludge. The suspicious spherical resin particles observed in S/G sludge sample were characterized for particle size distribution under optical microscope using the micro-technique, for element analysis by the electron probe micro analysis (EPMA), and for molecular identification by the IR spectroscopy The particle sizes are distributed from 1 to 200 ${\mu}m$ for the sludge, while 40 to 500 ${\mu}m$ for the spherical resin particles. The results of the elemental analysis showed different major impurities: Si, Al, Mn, Cr, Ni, Zn and Ti for the sludge particles, while Si, Cu, Zn for the spherical resin particles. However, both particles contain Fe as a matrix of hematite ($Fe_{3}O_4$). IR spectrum of the spherical particles was quite different from that of ion exchange resins used in S/G system. These results indicate that the spherical particles are not related to ion exchange resin particles and formed by the process of the sludge formation.

• The Journal of the Acoustical Society of Korea
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• v.27 no.7
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• pp.357-364
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• 2008

For the purpose of possibility study on development of an acoustic tweezer using standing waves and very high frequency ultrasound focused beams, a system which can manipulate the position of particles in water has been constructed. It can move the particles to near focal point of a focused beam by the radiation force of standing waves, and then the particles would be trapped by the radiating force of the focused beam. The results show that micro sphere particles were trapped well at nodes of the standing waves and their position can be easily manipulated by frequency control. And, even though the radiation force by single focused beam pushes a particle away from the transducer, two focused confronted beams can trap it at near center.

• Economic and Environmental Geology
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• v.54 no.2
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• pp.233-245
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• 2021

Many studies on the microstructures in rocks have been conducted using experimental methods with various equipment as well as natural rock studies to see the development of microstructures and understand their mechanisms. Grain boundary migration of mineral aggregates in rocks could cause grain growth or grain size changes during metamorphism or deformation as one of the main recrystallization mechanisms. This study suggests improved ways regarding the analog material experiments with reformed equipment to see sequential observations of these grain boundary migration. It can be more efficient than the existing techniques and carry out an appropriate microstructure analysis. This reformed equipment was implemented to enable optical manipulation by mounting polarizing plates capable of rotating operation on a stereoscopic microscope and a deformation rig capable of experimenting with analog materials. The equipment can automatically control the temperature and strain rate of the deformation rig by microcontrollers and programming and can take digital photomicrographs with constant time intervals during the experiment to observe any microstructure changes. The composite images synthesized using images by rotated polarizing plates enable us to see more accurate grain boundaries. As a rock analog material, norcamphor(C7H10O) was used, which has similar birefringence to quartz. Static grain growth and simple shear deformation experiments were performed using the norcamphor to verify the effectiveness of the equipment. The static grain growth experiments showed the characteristics of typical grain growth behavior. The number of grains decreases and the average grain size increases over time. These case experiments also showed a clear difference between the growth curves with three temperature conditions. The result of the simple shear deformation experiment under the medium temperature-low strain rate showed no significant change in the average grain size but presented the increased elongation of grain shapes in the direction of about 53° regarding the direction perpendicular to the shearing direction as the shear strain increases over time. These microstructures are interpreted as both the plastic deformation and the internal recovery process in grains are balanced by the deformation under the given experimental conditions. These experiments using the reformed equipment represent the ability to sequentially observe changing the microstructure during experiments as desired in the tests with the analog material during the entire process.

• The Journal of the Acoustical Society of Korea
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• v.39 no.5
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• pp.435-440
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• 2020

Single-beam acoustic tweezers that are capable of manipulating micron-size particles in a non-contact manner have been used in many biological and biomedical applications. Current single-beam acoustic tweezer systems developed for in vitro experiments consist of a function generator and a power amplifier, thus the system is bulky and expensive. This configuration would not be suitable for in vivo and clinical applications. Thus, in this paper, we present a portable single-beam acoustic tweezer system and its performances of trapping and manipulating micron-size objects. The developed system consists of an Field Programmable Gate Array (FPGA) chip and two pulsers, and parameters such as center frequency and pulse duration were controlled by a Personal Computer (PC) via a USB (Universal Serial Bus) interface in real-time. It was shown that the system was capable of generating the transmitting pulse up to 20 MHz, and producing sufficient intensity to trap microparticles and cells. The performance of the system was evaluated by trapping and manipulating 40 ㎛ and 90 ㎛ in diameter polystyrene particles.

• Korean Chemical Engineering Research
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• v.57 no.2
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• pp.149-163
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• 2019

Under non-uniform electric field, a directional force along the electric field gradient is applied to matter having permanent or induced dipoles. The transport of particles by the directional force is called dielectrophoresis (DEP). Since the strength and direction of the DEP force depend on parameters, such as permittivity and conductivity of particles and surrounding media, and frequency of the applied AC electric field, particle can be precisely manipulated by controlling the parameters. Moreover, unlike electrophoresis, DEP can be applied to any particles where dipole is effectively induced by electric field. Such a DEP technique has been used in various fields, ranging from microfluidic engineering to biosensor and microchip research. This paper first describes the fundamentals of DEP, and discusses representative microelectrode designs used for DEP study. Then, exemplary applications of DEP, such as separation, capture and self-assembly of particles, are introduced.