기하광학 영역에서의 광 집게 포획 효율 분석

김은선,김주하,이승석,최은서 한국물리학회 2017 새물리 Vol.67 No.6

본 논문에서는 광 포획 효율을 계산함으로써 광집게의 최적 실험조건을 연구하였다. 시뮬레이션을 수행하기 위해서 기하광학 영역에서 광집게에 대한 이론적인 모델을 마련하였다. 레이저의 파장이 입자의 크기보다 작은 경우를 고려하여 계산결과로부터 최적 실험조건에 대한 분석을 수행하였다. 광 집게력의 개구수, 입자크기, 그리고 입자의 굴절률에 따른 의존성을 분석 결과로부터 명확하게 제시할 수 있었다. 광 포획 효율은 개구수가 증가하면서 증가하였다. 하지만 최대 개구수 값은 1.3325로 제한되었다. 광 포획 효율은 작은 입자크기에서 좋은 결과를 보였다. 굴절률이 증가하면서 광 포획 효과는 줄어들고 1.4에서는 광 포획 효과가 광 밀어냄으로 바뀌었다. 계산된 결과부터 분석된 최적 조건은 효과적인 실험을 수행하는데 도움이 될 것이라고 생각된다. In this research, we studied the optimal experimental conditions of optical tweezers by calculating the light-trapping efficiency. For the simulation, a theoretical model for optical tweezers was designed in a geometrical region. By assuming the wavelength of the laser to be smaller than the particle size, we were able to determine the optimal experimental conditions. The dependencies of the optical tweezers' force on a numerical aperture (NA), the particle size, and the refractive index of a particle were clearly provided in the analysis results. The optical trapping efficiency increased when the NA increased, but the maximum NA was restricted to 1.3325. The optical trapping efficiency was better for smaller particle sizes. As the refractive index increased, the optical trapping effect decreased and changed to optical repulsion at a refractive index of 1.4. The optimal conditions determined by using the calculated results should be helpful for performing efficient experiments.

홀로그래픽 광집게를 이용한 마이크로 링의 포획

황선욱(Sun-Uk Hwang),김정대(Jun-Dae Kim),이용구(Yong-Gu Lee) (사)한국CDE학회 2011 한국 CAD/CAM 학회 학술발표회 논문집 Vol.2011 No.1

Optical tweezers use a tightly focused laser beam to hold and manipulate microscopic particles immersed in aqueous media. Due to the unique ability to easily grab and release objects, this technique is recently being used as a tool for micro-assembly. However, since not all micro-parts are symmetric in shape, simple single-beam trap geometry cannot always be used. In this paper, we present a method to manipulate ring-shaped micro-objects using holographic optical tweezers. To enable optical trapping of ring-shaped micro-objects (micro-rings), proposed method evenly distributes multiple traps produced by digital holography on the ring-shaped micro-object. By the ring-shaped trap pattern, micro-rings are trapped because the gradient force that attracts a mass towards focal spot with highest intensity is acting on the annular mass distribution of the object.

Investigation of the Polarization-dependent Optical Force in Optical Tweezers by Using Generalized Lorenz-Mie Theory

최재민,노희소 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.67 No.12

In vectorial diffraction theory, tight focusing of a linearly-polarized laser beam produces an anisotropic field distribution around the focal plane. We present a numerical investigation of the electromagnetic field distribution of a focused beam in terms of the input beam’s polarization state and the associated effects on the trap stiffness asymmetry of optical tweezers. We also explore the symmetry change of a polarization-dependent optical force due to the electromagnetic field redistribution in the presence of dielectric spheres of selected diameters ranging from the Rayleigh scattering regime to the Mie scattering regime.

Investigation of heterogeneous of ellipsoid particle interaction field using optical laser tweezers

최규환,강동우,박범준 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0

Heterogeneity among particles is their inherent feature, which makes the prediction of the properties of assembled structures and materials composed of many particles non-deterministic. Here, we report a promising strategy to quantify and visualize the field of heterogeneous and anisotropic interactions between non-spherical particles using the rotational measurement of optical laser tweezers. The mutual configuration and separation of two particles at an oil-water interface were optically controlled, and the corresponding capillary interaction behaviors were directly measured. As a result, the optimal particle configuration at an energetically favorable state was determined, depending on the interparticle distance. Visualization of the capillary field around individual particles demonstrated that the interface deformation by the presence of non-spherical particles and thus the capillary force were highly influenced by undulation of the meniscus as well as geodesic curvature.

Direct measurements of interparticle interactions in a low dielectric constant medium via optical laser tweezers

최규환,강동우,박범준 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1

When polymer particles are dispersed in an organic solvent or solvent mixtures with moderate dielectric constants, such as cyclohexyl bromide (CHB, ε = 7.92), a relatively small amount of surface charges are produced, whereas charge screening occurs less. The resulting electrostatic repulsive force between the particles is stronger than it is in aqueous dispersions. In this study, we added n-decane to CHB to lower the refractive index of the solvent. The increased visibility of PMMA particles dispersed in the liquid medium enabled direct measurements of the repulsive force between the particles. We varied the volume fraction of n-decane in the medium and measured the magnitude changes in the interactive forces between paired particles with optical laser tweezers.

Heterogeneous colloidal interactions field mapping method using optical laser tweezers

최규환,강동우,박범준 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0

Heterogeneity among particles is their inherent feature, which makes the prediction of the properties of assembled structures and materials composed of many particles non-deterministic. Here, we report a promising strategy to quantify and visualize the field of heterogeneous and anisotropic interactions between non-spherical particles using the rotational measurement of optical laser tweezers. The mutual configuration and separation of two particles at an oil-water interface were optically controlled, and the corresponding capillary interaction behaviors were directly measured. As a result, the optimal particle configuration at an energetically favorable state was determined, depending on the interparticle distance. Visualization of the capillary field around individual particles demonstrated that the interface deformation by the presence of non-spherical particles and thus the capillary force were highly influenced by undulation of the meniscus as well as geodesic curvature.

Identification of Dipole-Induced Dipole in a Multiphasic Colloid System

김용우,박범준 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-

When dielectric microspheres diffuse at the fluid-fluid interface, they exhibit strong and repulsive interactions. This phenomenon occurs due to the dissociation of the asymmetrical surface charges, the formation of electrical dipoles around the particles trapped at the interface. Direct measurements and analysis of the measure d interaction force consistently demonstrated electrostatic dipole interactions between particles confined to the o/w interface. We assumed that dipole formed around the particles at the interface could rearrange the counter ions in the aqueous phase. If other particles approach to the interface, this rearrangement can cause unexpected attraction. We quantitatively studied this dipole-induced dipole interaction using time-sharing optical laser tweezers.

Direct measurements of colloidal hydrodynamics near flat boundaries using oscillating optical tweezers

Ha, C.,Ou-Yang, H.D.,Pak, H.K. North-Holland 2013 PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIO Vol.392 No.17

We studied the hydrodynamic interaction between a colloidal particle close to flat rigid boundaries and the surrounding fluid using oscillating optical tweezers. A colloidal particle located near walls provides a model system to study the behavior of more complex systems whose boundaries can be modeled as effective walls, such as a blood tube, cell membrane, and capillary tube in bio-MEMS. In this study, we measure the hydrodynamic interaction directly without using the Stokes-Einstein relation. Two different cases are studied: a colloidal sphere near a single flat wall and a colloidal sphere located at the midplane between two flat walls. The colloidal hydrodynamics is measured as a function of the distance between the particle and the walls, and is compared with the theoretical results from well-defined hydrodynamics approximations.

Demonstration of unusual colloidal interaction via optical laser tweezers: Dipole-induced dipole attraction due to counterion rearrangements around colloidal particles near the oil-water interface

박범준 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-

We use the optical laser tweezer apparatus to investigate the dipoleinduced dipole attraction between colloidal particles that has not been reported yet. We postulate that the perpendicular electric dipole formed around a particle at an oil-water interface leads to rearrangements of surrounding counterions in the aqueous phase. The rearrangements can cause unexpected attractions when another particle dispersed in water approaches the interface-trapped particle nearby. We quantitatively measure the dipole-induced dipole electrostatic interactions and the critical time of counterion migration for generating the attractive force that can overcome the double layer interaction as well as the thermal fluctuation.

광집게를 이용한 마이크로 부품의 안정적 포획, 이송 및 회전

김정대(Jung-Dae Kim),박윤희(Yun-Hui Park),황선욱(Sun-Uk Hwang),이용구(Yong-Gu Lee) (사)한국CDE학회 2010 한국 CAD/CAM 학회 학술발표회 논문집 Vol.2010 No.1

Two-photon polymerization (TPP) is a very attractive three-dimensional (3D) rapid micro-structuring technology which can be used to create micrometer sized parts. Joining these parts and making assemblies will entail functional mechanisms that can develop to micro-machines. So, for the sake of such assemblies, the micro parts handling is quite important. The common assembling processes enlist grabbing, translation and rotation. In this paper, we present a method showing stable trapping, translation and rotation of complex shaped parts using optical tweezers.