Yuanqiang Peng, Xiaolin Wu, Yunqi Li and Weiyi Hong
The dynamics of the inward-focusing ring Airy beam in the defocusing nonlinear media is investigated. It is found an interesting phenomenon that the propagation of the inward-focusing ring Airy beam exhibits a "funnel" when the beam intensity is sufficiently high. Additionally, the focus spot of such a funnel beam monotonously changes with the nonlocality of the media. The gradient force of the funnel beam is also studied in detail. The findings may pave the way to the optical tweezers in the nonlinear regime.
DOI
Showing posts with label Japanese Journal of Applied Physics. Show all posts
Showing posts with label Japanese Journal of Applied Physics. Show all posts
Wednesday, September 25, 2019
Monday, July 15, 2019
Non-uniform stochastic dynamics of nanoparticle clusters at a solid–liquid interface induced by laser trapping
Itsuo Hanasaki and Chie Hosokawa
We reveal the characteristics of Brownian motion in nanoparticle clusters formed by the optical force fields at a solid–liquid interface based on the trajectory analysis from the microscopy movie data. The characteristics of stochastic motion depend not only on the laser power but also on the location in the clusters. The particles at the focal points exhibit smaller displacements, compared to the surrounding particles that are nevertheless trapped. The nominal diffusion coefficient is larger than the bulk at sufficiently small time scale for sufficiently high laser powers, although it decreases as a function of time because of the confinement. Decomposition of radial and circumferential components of displacements reveals the anisotropy as well as non-uniformity of the dynamics.
DOI
We reveal the characteristics of Brownian motion in nanoparticle clusters formed by the optical force fields at a solid–liquid interface based on the trajectory analysis from the microscopy movie data. The characteristics of stochastic motion depend not only on the laser power but also on the location in the clusters. The particles at the focal points exhibit smaller displacements, compared to the surrounding particles that are nevertheless trapped. The nominal diffusion coefficient is larger than the bulk at sufficiently small time scale for sufficiently high laser powers, although it decreases as a function of time because of the confinement. Decomposition of radial and circumferential components of displacements reveals the anisotropy as well as non-uniformity of the dynamics.
DOI
Thursday, October 25, 2018
Photothermal dynamics of micro-glass beads coated with gold nanoparticles in water: Fine bubble generation and fluid-induced laser trapping
Shin-ichiro Yanagiya, Naoya Sekimoto and Akihiro Furube
In this study, gold nanoparticles were heterogeneously deposited onto the surfaces of glass beads through a gold ion reduction method to obtain "plasmonic beads". Plasmonic beads in pure water were illuminated with a visible continuous-wave laser through an objective lens. Using a relatively low-power laser, plasmonic beads were optically trapped and aggregated the other beads over an area much greater than the focal point. On the other hand, using a high-power laser (>20 mW/µm2), microbubbles were produced in water. Thus, the plasmonic beads studied herein can act as optically controllable fluid and microbubble generators.
DOI
In this study, gold nanoparticles were heterogeneously deposited onto the surfaces of glass beads through a gold ion reduction method to obtain "plasmonic beads". Plasmonic beads in pure water were illuminated with a visible continuous-wave laser through an objective lens. Using a relatively low-power laser, plasmonic beads were optically trapped and aggregated the other beads over an area much greater than the focal point. On the other hand, using a high-power laser (>20 mW/µm2), microbubbles were produced in water. Thus, the plasmonic beads studied herein can act as optically controllable fluid and microbubble generators.
DOI
Monday, April 30, 2018
Evaluation of mitochondrial activity by two-photon absorption with near-field multioptical fiber probes
Yasuaki Kanazashi, Naoshi Takara, Kentaro Iwami, Yoshihiro Ohta and Norihiro Umeda
pH measurements enable the direct monitoring and evaluation of mitochondrial activity. We constructed a scanning near-field optical microscopy system with multioptical fiber probes using the two-photon absorption of a pH-sensitive fluorescent dye, SNARF-4F, to measure the activity difference of mitochondrial aggregates. pH can be monitored through the fluorescence intensity ratio (FIR) of SNARF-4F. We derived a calibration curve of the FIR as a function of pH. The FIR dynamic responses were measured by adding hydrochloric acid to the buffer solution. Using the developed system, we simultaneously measured the pH changes at two different locations in the SNARF-4F solution. Mitochondrial samples were prepared using optical tweezers to control the number and position of mitochondria. Mitochondrial pH changes (ΔpH) between 0.05 and 0.57 were observed after adding a nutritional supplement (malate and glutamate). In addition, in the comparative experiment on the activities of two mitochondrial populations, the obtained result suggested that the activity differs depending on the difference in the number of mitochondria.
DOI
pH measurements enable the direct monitoring and evaluation of mitochondrial activity. We constructed a scanning near-field optical microscopy system with multioptical fiber probes using the two-photon absorption of a pH-sensitive fluorescent dye, SNARF-4F, to measure the activity difference of mitochondrial aggregates. pH can be monitored through the fluorescence intensity ratio (FIR) of SNARF-4F. We derived a calibration curve of the FIR as a function of pH. The FIR dynamic responses were measured by adding hydrochloric acid to the buffer solution. Using the developed system, we simultaneously measured the pH changes at two different locations in the SNARF-4F solution. Mitochondrial samples were prepared using optical tweezers to control the number and position of mitochondria. Mitochondrial pH changes (ΔpH) between 0.05 and 0.57 were observed after adding a nutritional supplement (malate and glutamate). In addition, in the comparative experiment on the activities of two mitochondrial populations, the obtained result suggested that the activity differs depending on the difference in the number of mitochondria.
DOI
Friday, October 27, 2017
Local electrophoresis deposition assisted by laser trapping coupled with a spatial light modulator for three-dimensional microfabrication
Toshiki Matsuura, Takanari Takai and Futoshi Iwata
We describe a novel three-dimensional fabrication technique using local electrophoresis deposition assisted by laser trapping coupled with a spatial light modulator (SLM). In a solution containing nanometer-scale colloidal Au particles, multiple laser spots formed on a conductive substrate by the SLM gathered the nanoparticles together, and then the nanoparticles were electrophoretically deposited onto the substrate by an applied electrical field. However, undesirable sub-spots often appeared due to optical interference from the multiple laser spots, which deteriorated the accuracy of the deposition. To avoid the appearance of undesirable sub-spots, we proposed a method using quasi-multiple spots, which we realized by switching the position of a single spot briefly using the SLM. The method allowed us to deposit multiple dots on the substrate without undesirable sub-dot deposition. By moving the substrate downward during deposition, multiple micro-pillar structures could be fabricated. As a fabrication property, the dependence of the pillar diameter on laser intensity was investigated by changing the number of laser spots. The smallest diameter of the four pillars fabricated in this study was 920 nm at the laser intensity of 2.5 mW. To demonstrate the effectiveness of the method, multiple spiral structures were fabricated. Quadruple spirals of 46 µm in height were successfully fabricated with a growth rate of 0.21 µm/s using 2200 frames of the CGH patterns displayed in the SLM at a frame rate of 10 fps.
DOI
We describe a novel three-dimensional fabrication technique using local electrophoresis deposition assisted by laser trapping coupled with a spatial light modulator (SLM). In a solution containing nanometer-scale colloidal Au particles, multiple laser spots formed on a conductive substrate by the SLM gathered the nanoparticles together, and then the nanoparticles were electrophoretically deposited onto the substrate by an applied electrical field. However, undesirable sub-spots often appeared due to optical interference from the multiple laser spots, which deteriorated the accuracy of the deposition. To avoid the appearance of undesirable sub-spots, we proposed a method using quasi-multiple spots, which we realized by switching the position of a single spot briefly using the SLM. The method allowed us to deposit multiple dots on the substrate without undesirable sub-dot deposition. By moving the substrate downward during deposition, multiple micro-pillar structures could be fabricated. As a fabrication property, the dependence of the pillar diameter on laser intensity was investigated by changing the number of laser spots. The smallest diameter of the four pillars fabricated in this study was 920 nm at the laser intensity of 2.5 mW. To demonstrate the effectiveness of the method, multiple spiral structures were fabricated. Quadruple spirals of 46 µm in height were successfully fabricated with a growth rate of 0.21 µm/s using 2200 frames of the CGH patterns displayed in the SLM at a frame rate of 10 fps.
DOI
Monday, August 1, 2016
Optical two-beam traps in microfluidic systems
Kirstine Berg-Sørensen
An attractive solution for optical trapping and stretching by means of two counterpropagating laser beams is to embed waveguides or optical fibers in a microfluidic system. The microfluidic system can be constructed in different materials, ranging from soft polymers that may easily be cast in a rapid prototyping manner, to hard polymers that could even be produced by injection moulding, or to silica in which waveguides may either be written directly, or with grooves for optical fibers. Here, we review different solutions to the system and also show results obtained in a polymer chip with DUV written waveguides and in an injection molded polymer chip with grooves for optical fibers.
DOI
An attractive solution for optical trapping and stretching by means of two counterpropagating laser beams is to embed waveguides or optical fibers in a microfluidic system. The microfluidic system can be constructed in different materials, ranging from soft polymers that may easily be cast in a rapid prototyping manner, to hard polymers that could even be produced by injection moulding, or to silica in which waveguides may either be written directly, or with grooves for optical fibers. Here, we review different solutions to the system and also show results obtained in a polymer chip with DUV written waveguides and in an injection molded polymer chip with grooves for optical fibers.
DOI
Wednesday, May 25, 2016
Surface plasmon-enhanced optical trapping of quantum-dot-conjugated surface molecules on neurons cultured on a plasmonic chip
Kohei Miyauchi, Keiko Tawa, Suguru N. Kudoh, Takahisa Taguchi and Chie Hosokawa
Living neurons in a complex neuronal network communicate with each other through synaptic connections. The molecular dynamics of cell surface molecules localized at synaptic terminals is essential for functional connections via synaptic plasticity in the neuronal network. Here, we demonstrate surface-plasmon-resonance-based optical trapping using a plasmonic chip toward realizing effective manipulation of molecules on the surface of neurons. Surface-plasmon-enhanced optical trapping was evaluated by the fluorescence analysis of nanoparticles suspended in water and neural cell adhesion molecules (NCAMs) labeled with quantum dots (Q-dots) on rat hippocampal neurons. The motion of nanoparticles in water and the molecular dynamics of NCAMs on neuronal cells cultured on a plasmonic chip were constrained at the laser focus more effectively than those on a glass substrate because of the surface plasmon resonance effect.
DOI
Living neurons in a complex neuronal network communicate with each other through synaptic connections. The molecular dynamics of cell surface molecules localized at synaptic terminals is essential for functional connections via synaptic plasticity in the neuronal network. Here, we demonstrate surface-plasmon-resonance-based optical trapping using a plasmonic chip toward realizing effective manipulation of molecules on the surface of neurons. Surface-plasmon-enhanced optical trapping was evaluated by the fluorescence analysis of nanoparticles suspended in water and neural cell adhesion molecules (NCAMs) labeled with quantum dots (Q-dots) on rat hippocampal neurons. The motion of nanoparticles in water and the molecular dynamics of NCAMs on neuronal cells cultured on a plasmonic chip were constrained at the laser focus more effectively than those on a glass substrate because of the surface plasmon resonance effect.
DOI
Friday, January 11, 2013
To Study the Effect of Paclitaxel on the Cytoplasmic Viscosity of Murine Macrophage Immune Cell RAW 264.7 Using Self-Developed Optical Tweezers System
Ying-chun Chen and Chien-ming Wu
In recent years, optical tweezers have become one of the tools to measure the mechanical properties of living cells. In this study, we first constructed an optical tweezers to investigate the cytoplasmic viscosity of immune cells. In addition to measuring viscosity of cells in a normal condition, we also treated cells with anti-cancer drug, Paclitaxel, and in order to study its effect on the cytoplasmic viscosity. The results showed that the viscosity decreased dramatically during the first 3 h. After 3 h, the change started to slow down and it remained nearly flat by the end of the experiment. In addition, we used the confocal laser scanning microscope to observe the cytoskeleton of the cell after drug treatment for 3 and 5 h, respectively, and found that actin filaments were disrupted and that the nucleus had disintegrated in some drug-treated cells, similar to the process of apoptosis. This study presents a new way for measuring the changes in cytoplasmic viscosity, and to determine if a cell is going into apoptosis as a result of a drug treatment.
In recent years, optical tweezers have become one of the tools to measure the mechanical properties of living cells. In this study, we first constructed an optical tweezers to investigate the cytoplasmic viscosity of immune cells. In addition to measuring viscosity of cells in a normal condition, we also treated cells with anti-cancer drug, Paclitaxel, and in order to study its effect on the cytoplasmic viscosity. The results showed that the viscosity decreased dramatically during the first 3 h. After 3 h, the change started to slow down and it remained nearly flat by the end of the experiment. In addition, we used the confocal laser scanning microscope to observe the cytoskeleton of the cell after drug treatment for 3 and 5 h, respectively, and found that actin filaments were disrupted and that the nucleus had disintegrated in some drug-treated cells, similar to the process of apoptosis. This study presents a new way for measuring the changes in cytoplasmic viscosity, and to determine if a cell is going into apoptosis as a result of a drug treatment.
Friday, October 26, 2012
Plasmon-Based Optical Trapping of Polymer Nano-Spheres as Explored by Confocal Fluorescence Microspectroscopy: A Possible Mechanism of a Resonant Excitation Effect
Tatsuya Shoji, Yoshihiko Mizumoto, Hajime Ishihara, Noboru Kitamura, Mai Takase, Kei Murakoshi, and Yasuyuki Tsuboi
In optical trapping using photon force much enhanced by localized surface plasmon (LSP) in solution, we found that a resonant excitation effect can further enhance photon force. In this LSP-based optical trapping under a resonant excitation condition, an incident laser beam excites both LSP and electronic resonant transition of a target object simultaneously. Fluorescence microspectroscopy clearly showed that nanospheres under the resonant condition were much more efficiently trapped as compared to that under a non-resonant condition. The resonant LSP-based trapping mechanism was further reinforced by theoretical calculations taking the resonant excitation effect into account. Such resonant LSP-based trapping methodology will provide a novel approach for efficient trapping of small molecules.
In optical trapping using photon force much enhanced by localized surface plasmon (LSP) in solution, we found that a resonant excitation effect can further enhance photon force. In this LSP-based optical trapping under a resonant excitation condition, an incident laser beam excites both LSP and electronic resonant transition of a target object simultaneously. Fluorescence microspectroscopy clearly showed that nanospheres under the resonant condition were much more efficiently trapped as compared to that under a non-resonant condition. The resonant LSP-based trapping mechanism was further reinforced by theoretical calculations taking the resonant excitation effect into account. Such resonant LSP-based trapping methodology will provide a novel approach for efficient trapping of small molecules.
Friday, July 6, 2012
Optical Tweezers-Assisted Cross-Correlation Analysis for a Non-intrusive Fluid Temperature Measurement in Microdomains
Chih-Ming Cheng, Ming-Chih Chang, Yu-Fen Chang, Wei-Ting Wang, Chien-Ting Hsu, Jing-Shin Tsai, Chia-Yeh Liu, Chien-Ming Wu, Keng-Liang Ou, and Tzu-Sen Yang
An image-based approach to predict the fluid temperature in microfluidic flow cell is presented. We apply Fourier-based cross-correlation processing to determine the lateral displacement of the optically trapped bead; therefore, both the mean square displacement (MSD) and the diffusion coefficient (D) can be obtained. On the other hand, applying the Stokes–Einstein equation, together with Faxen's law correction, the theoretical relation showed that D is proportional to (T/η), where Tand η are temperature and temperature-dependent fluid viscosity, respectively. Hence, the fluid temperature can be determined by MSD-based thermometry.
DOI
An image-based approach to predict the fluid temperature in microfluidic flow cell is presented. We apply Fourier-based cross-correlation processing to determine the lateral displacement of the optically trapped bead; therefore, both the mean square displacement (MSD) and the diffusion coefficient (D) can be obtained. On the other hand, applying the Stokes–Einstein equation, together with Faxen's law correction, the theoretical relation showed that D is proportional to (T/η), where Tand η are temperature and temperature-dependent fluid viscosity, respectively. Hence, the fluid temperature can be determined by MSD-based thermometry.
DOI
Friday, November 18, 2011
Optical Trapping of Beads and Jurkat Cells Using Micromachined Fresnel Zone Plate Integrated with Microfluidic Chip
Ju-Nan Kuo and Han-Zhong Hu
This paper presents a method for trapping beads and cells using a single-beam optical tweezer and a Fresnel zone plate integrated with a microfluidic chip. The experimental results show that a laser power of 2.4 mW is sufficient to trap 3-µm-diameter polystyrene beads, while a laser power of 1.5 mW is sufficient to trap individual Jurkat cells. The Fresnel zone plate developed in this study has many advantages, including a small size, a straightforward fabrication process, and a simple integration with microfluidic chips. Consequently, it provides an ideal solution for the trapping of a wide range of biological cells for analysis purposes.
DOI
This paper presents a method for trapping beads and cells using a single-beam optical tweezer and a Fresnel zone plate integrated with a microfluidic chip. The experimental results show that a laser power of 2.4 mW is sufficient to trap 3-µm-diameter polystyrene beads, while a laser power of 1.5 mW is sufficient to trap individual Jurkat cells. The Fresnel zone plate developed in this study has many advantages, including a small size, a straightforward fabrication process, and a simple integration with microfluidic chips. Consequently, it provides an ideal solution for the trapping of a wide range of biological cells for analysis purposes.
DOI
Friday, January 7, 2011
Multiple Optical Traps with a Single-Beam Optical Tweezer Utilizing Surface Micromachined Planar Curved Grating
Kuo, Ju-Nan; Chen, Kuan-Yu
In this paper, we present a single-beam optical tweezer integrated with a planar curved diffraction grating for microbead manipulation. Various curvatures of the surface micromachined planar curved grating are systematically investigated. The planar curved grating was fabricated using multiuser micro-electro-mechanical-system (MEMS) processes (MUMPs). The angular separation and the number of diffracted orders were determined. Experimental results indicate that the diffraction patterns and curvature of the planar curved grating are closely related. As the curvature of the planar curved grating increases, the vertical diffraction angle increases, resulting in the strip patterns of the planar curved grating. A single-beam optical tweezer integrated with a planar curved diffraction grating was developed. We demonstrate a technique for creating multiple optical traps from a single laser beam using the developed planar curved grating. The strip patterns of the planar curved grating that resulted from diffraction were used to trap one row of polystyrene beads.
DOI
In this paper, we present a single-beam optical tweezer integrated with a planar curved diffraction grating for microbead manipulation. Various curvatures of the surface micromachined planar curved grating are systematically investigated. The planar curved grating was fabricated using multiuser micro-electro-mechanical-system (MEMS) processes (MUMPs). The angular separation and the number of diffracted orders were determined. Experimental results indicate that the diffraction patterns and curvature of the planar curved grating are closely related. As the curvature of the planar curved grating increases, the vertical diffraction angle increases, resulting in the strip patterns of the planar curved grating. A single-beam optical tweezer integrated with a planar curved diffraction grating was developed. We demonstrate a technique for creating multiple optical traps from a single laser beam using the developed planar curved grating. The strip patterns of the planar curved grating that resulted from diffraction were used to trap one row of polystyrene beads.
DOI
Tuesday, September 28, 2010
Stability Analysis of Particle Trapping in Time-Division Optical Tweezers by the Generalized Lorentz–Mie Theory
Johtaro Yamamoto and Toshiaki Iwai
Time-division multiplexing in the proposed holographic optical tweezers (HOT) has been used to quasi-simultaneously generate two different intensity patterns, a carrier beam spot and a beam array, by alternately feeding the corresponding hologram patterns to a spatial light modulator (SLM). Since the switching of the input holograms degrades the spatial stability of trapping a Brownian particle within the generated intensity spot area, it is necessary to numerically investigate the conditions in the time-division multiplexing for a particle to be stably trapped by a focused Gaussian beam. The Smoluchowski equation based on the generalized Lorentz–Mie theory (GLMT) model is evaluated numerically by an explicit method to estimate the relationship among particle size, switching rate, and focused laser beam power. Finally, the validity of the numerical analysis in this work is confirmed by experiments.
DOI
Time-division multiplexing in the proposed holographic optical tweezers (HOT) has been used to quasi-simultaneously generate two different intensity patterns, a carrier beam spot and a beam array, by alternately feeding the corresponding hologram patterns to a spatial light modulator (SLM). Since the switching of the input holograms degrades the spatial stability of trapping a Brownian particle within the generated intensity spot area, it is necessary to numerically investigate the conditions in the time-division multiplexing for a particle to be stably trapped by a focused Gaussian beam. The Smoluchowski equation based on the generalized Lorentz–Mie theory (GLMT) model is evaluated numerically by an explicit method to estimate the relationship among particle size, switching rate, and focused laser beam power. Finally, the validity of the numerical analysis in this work is confirmed by experiments.
DOI
Monday, July 26, 2010
Measurement of Macrophage Adhesion at Various pH Values by Optical Tweezers with Backward-Scattered Detection
Yi-Jr Su and Long Hsu
Optical tweezers have emerged as a powerful tool with broad applications in biology and physics. In force-measuring applications, the trapped bead position is usually accurately determined by forward-scattered detection. The current study discusses both backward-scattered detection and forward-scattered detection related to the linear detection range for a 3 µm bead and the distance between the two laser system focuses, confirming the optimum positions of the two focuses. The result indicates that the linear detection range of backward-scattered detection is longer than the forward-scattered one. Finally, this work investigates real-time adhesion force measurements between human macrophages and 3 µm trapped beads coated with lipopolysaccharides at various pH values by optical tweezers with backward-scattered detection.
Optical tweezers have emerged as a powerful tool with broad applications in biology and physics. In force-measuring applications, the trapped bead position is usually accurately determined by forward-scattered detection. The current study discusses both backward-scattered detection and forward-scattered detection related to the linear detection range for a 3 µm bead and the distance between the two laser system focuses, confirming the optimum positions of the two focuses. The result indicates that the linear detection range of backward-scattered detection is longer than the forward-scattered one. Finally, this work investigates real-time adhesion force measurements between human macrophages and 3 µm trapped beads coated with lipopolysaccharides at various pH values by optical tweezers with backward-scattered detection.
Monday, June 7, 2010
Assembly of Acircular SnO2 Rod Using Optical Tweezers and Laser Curing of Metal Nanoparticles
Chanhyuk Nam, Daehie Hong, Jaeik Chung, Jaewon Chung, Insung Hwang, Jongheun Lee, Seunghwan Ko, and Costas P. Grigoropoulos
Acicular tin dioxide (SnO2) rods (1–2 µm in diameter, 5–20 µm long) were assembled and fused on the patterned gold electrode by an optical tweezer. In addition, the electrical contact between the assembled SnO2 rod and the gold electrode was improved by laser curing of gold nanoparticles and the subsequent sintering in the oven. Here, the nanoparticles covered the entire area of the assembled SnO2 rod by evaporating a droplet of nanoparticle solution dripped on the assembled SnO2 rod. Subsequently, nanoparticles near the contact area between the rod and electrode were locally cured by direct heating with a focused infrared laser beam, which induced desorption of the surface monolayer. Therefore, the cured gold nanoparticles could be sintered after the non-laser irradiated nanoparticles were cleaned by the initial solvent application. Without sintering of the nanoparticles, the resistance of the assembled SnO2 rod was measured over several MΩ. After the nanoparticle sintering it could be reduced to a few hundred kΩ, which was in agreement with the resistance of the assembled SnO2 rod.
DOI
DOI
Tuesday, February 2, 2010
Cell Palpation System Based on a Force Measurement by Optical Tweezers for Investigation of Local Mechanical Properties of a Cell Membrane
Hideaki Miyoshi, Tadao Sugiura, and Kotaro Minato
We have developed a cell palpation system, which enables to investigate mechanical properties of a cell in local with an optically manipulated particle. In this system, the particle attached on a cell surface is forced to move back-and-forth in sinusoidal manner by optical tweezers. Position of the particle position is recorded and analyzed to extract force exerted on the particle by using a physical model of the particle. We have demonstrated to measure cell membrane stiffness in local and temporal change of that with the detection limit of the force in pN order.
We have developed a cell palpation system, which enables to investigate mechanical properties of a cell in local with an optically manipulated particle. In this system, the particle attached on a cell surface is forced to move back-and-forth in sinusoidal manner by optical tweezers. Position of the particle position is recorded and analyzed to extract force exerted on the particle by using a physical model of the particle. We have demonstrated to measure cell membrane stiffness in local and temporal change of that with the detection limit of the force in pN order.
Thursday, August 13, 2009
Study of the Line Optical Tweezers Characteristics Using a Novel Method and Establishing a Model for Cell Sorting
Ho-Chien Lin and Long Hsu
Optical tweezers have become a powerful tool in cellular and molecule biology. Line optical tweezers enhanced its function in cell sorting. This study presents the line trap model, based on the ray-optics model, and demonstrates its accuracy for the line optical tweezers. The line optical tweezers system is established to produce the optical intensity distribution of a line pattern and to trap the micro-sized beads. The main parameter, optical intensity distribution, is used to calculate the trapping force distribution in the model. The two forces, trapping force and water dragging force, and the equation of motion is used to simulate the trajectory of micro-sized beads as they pass through the line pattern in flowing water in the microchannel. The trajectory is analyzed to determine the effective separation distance between the micro-sized beads or cells. The method will be applied in biological and medical detection.
Optical tweezers have become a powerful tool in cellular and molecule biology. Line optical tweezers enhanced its function in cell sorting. This study presents the line trap model, based on the ray-optics model, and demonstrates its accuracy for the line optical tweezers. The line optical tweezers system is established to produce the optical intensity distribution of a line pattern and to trap the micro-sized beads. The main parameter, optical intensity distribution, is used to calculate the trapping force distribution in the model. The two forces, trapping force and water dragging force, and the equation of motion is used to simulate the trajectory of micro-sized beads as they pass through the line pattern in flowing water in the microchannel. The trajectory is analyzed to determine the effective separation distance between the micro-sized beads or cells. The method will be applied in biological and medical detection.
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