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1.
The dynamics of motion of microparticles in a gradient light field depending on the acting radiation time sequences has been studied theoretically and experimentally. A water suspension of small polymeric balls illuminated by interference fringes of the radiation from a cw He–Ne laser ( = 632.8 nm) and also pulse-periodic YAG:Nd3+ laser ( = 532.1 nm; p 17 nsec; f 50 Hz) was used. It has been established that the gradient field generated by continuous radiation ensures a higher velocity for transporting particles and, consequently, a more effective change in their local concentration and acceleration of their diffusion. In contrast to this, interference irradiation of particles by short repetitive pulses is not very effective for their transportation in space but ensures much higher instantaneous velocities and a higher kinetic energy. As applied to biological objects, this regime has a slight effect on the local concentration and diffusion of particles, but can cause conformational changes in biological structures. 相似文献
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Optical tweezers have been a valuable research tool since their invention in the 1980s. One of the most important developments in optical tweezers in recent years is the creation of two-dimensional arrays of optical traps. In this paper, a method based on interference is discussed to form gradient laser fields, which may cause the spatial modulation of particle concentration. The parameters related to the optical tweezers array are discussed in detail and simulated by the Matlab software to show the influence of important parameters on the distribution of particle concentration. The spatial redistribution of particles in a laser interference field can also be predicted according to the theoretical analysis. 相似文献
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Joseph L. Lawson Nathan J. Jenness Robert L. Clark 《Particle & Particle Systems Characterization》2015,32(7):734-742
Optical trapping and magnetic trapping are common micromanipulation techniques for controlling colloids including micro‐ and nanoparticles. Combining these two manipulation strategies allows a larger range of applied forces and decoupled control of rotation and translation; each of which are beneficial properties for many applications including force spectroscopy and advanced manufacturing. However, optical trapping and magnetic trapping have conflicting material requirements inhibiting the combination of these methodologies. In this paper, anisotropic microscaled particles capable of being simultaneously controlled by optical and magnetic trapping are synthesized using a glancing angle deposition (GLAD) technique. The anisotropic alignment of dielectric and ferromagnetic materials limits the optical scattering from the metallic components which typically prevents stable optical trapping in three dimensions. Compared to the current state of the art, the benefits of this approach are twofold. First, the composite structure allows larger volumes of ferromagnetic material so that larger magnetic moments may be applied without inhibiting the stability of optical trapping. Second, the robustness of the synthesis process is greatly improved. The dual optical and magnetic functionality of the synthesized colloids is demonstrated by simultaneously optically translating and magnetically rotating a magnetic GLAD particle using a custom designed optomagnetic trapping system. 相似文献
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Systematical study of the trapping forces of optical tweezers formed by different types of optical ring beams 总被引:2,自引:0,他引:2 下载免费PDF全文
The technique of optical tweezers has been improved a lot since its
invention, which extends the application fields of optical tweezers. Besides
the conventionally used Gaussian beams, different types of ring beams have also been
used to form optical tweezers for different purposes. The two typical
kinds of ring beams used in optical tweezers are the hollow Gaussian beam and
Laguerre--Gaussian (LG) beam. Both theoretical computation and experiments
have shown that the axial trapping force is improved for the ring beams
compared with the Gaussian beam, and hence the trapping stability is
improved, although the transverse trapping forces of ring beams are smaller
than that of Gaussian beam. However, no systematic study on the trapping
forces of ring beam has ever been discussed. In this article, we will investigate
the axial and transverse trapping forces of different types of ring beams
with different parameters systematically, by numerical computation in which
the ray optics model is adopted. The spherical aberration caused by the
refractive index mismatch between oil and water is also considered in the
article. The trapping forces for different objectives that obey the sine
condition and tangent condition are also compared with each other.
The result of systematical calculation will be useful for the applications
of optical tweezers formed by different types of ring beams. 相似文献
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光镊技术被广泛应用在俘获和操纵微纳米尺寸颗粒, 目前被研究学者普遍接受的俘获吸光性颗粒的机理为光泳力. 本文实现了对空气中被俘获的吸光性颗粒的红外显微观测. 当激光器功率为1.0 W时, 成功观测到被俘获墨粉颗粒(直径约7 μm)和甲苯胺蓝颗粒(直径约为1–20 μm)的温升约为14 K, 为光泳力理论提供了强有力的证据. 另外, 首次用可见光显微镜和红外显微镜同时观测到被俘获颗粒的周期振荡现象, 并分析了振荡现象的产生机理.
关键词:
光镊
光俘获
红外显微 相似文献
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Trapping force of an optical tweezers system with an oil immersion objective is calculated with a ray-optics model. Results indicate that the trapping force will be decreased as a result of the introduction of spherical aberration, which is caused by the refractive mismatch between objective oil and water, when the sample manipulated is suspended in a water solution. The effect of spherical aberration will be serious when the detection depth of the optical tweezers is enhanced. 相似文献
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Calculation of axial optical forces exerted on medium-sized particles by optical trap 总被引:1,自引:0,他引:1
Fang-Lin Mao Qi-Rong Xing Kai Wang Li-Ying Lang Lu Chai Qing-Yue Wang 《Optics & Laser Technology》2007,39(1):34-39
Optical trapping has become an efficient technique of trapping and manipulating micrometer and sub-micrometer dimension particles. Particles in the range between the applicable regime of ray optics theory (ROT) and the Rayleigh regime (so-called medium-sized particles) are focused on. By using ROT and the generalized Lorenz–Mie theory (GLMT), axial optical forces and their dependences on particle sizes and beam waists are presented. Furthermore, by comparing the numerical results of these two theories, the applicability of the GLMT to particles of arbitrary size and the limit of ROT in the region of small particles are analyzed. A new criterion of the applicable region of ROT is obtained, i.e. the relative particle size β=2πa/λ20, where a is the particle radius and λ is the wavelength of light. The theoretical results will be of great help to the design and optimization of the most efficient optical trap. 相似文献
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本文采用三维时域有限差分法(FDTD)和Maxwell应力张量法建立了单光镊在焦点附近俘获球形微粒的光阱力模型,采用基于球矢量波函数(VSWF)的五阶高斯光源作为仿真光源,得到了准确的光场传播.讨论了光源的波长、束腰、偏振态和微球的半径、折射率对光阱力的影响,分析了在单光镊俘获微球时,邻近微球对光阱力的影响.特别研究了光源的偏振态对微球所受光阱力的作用效果,仿真结果表明圆偏振光比线偏振光对微球的俘获力更大;被光镊稳定俘获的微球,会受到邻近微球干扰,失去平衡状态,改变光源的偏振态可以改变微球的受力状态.
关键词:
光镊
光阱力
介质微球
时域有限差分法(FDTD) 相似文献
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We report a new, simplified mechanism for performing micro-rotation. A sample chamber filled with aqueous solution and mounted on a piezoelectric transducer (PZT)-driven stage was used to produce flow-induced torque for rotating micro-objects. We demonstrated the scheme by rotating ellipsoidal yeast particles and a two-sphere system with 20 mW of laser power. Clockwise or counterclockwise rotation could be controlled by changing the initial angular position of the object trapped and by reversing the direction of the PZT-driven stage. This mechanism has potential applications in microfabrication, biotechnology and fluidic technology. 相似文献
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Subwavelength features in conjunction with light‐guiding structures have gained significant interest in recent decades due to their wide range of applications to particle and atom trapping. Lately, the focus of particle trapping has shifted from the microscale to the nanoscale. This few orders of magnitude change is driven, in part, by the needs of life scientists who wish to better manipulate smaller biological samples. Devices with subwavelength features are excellent platforms for shaping local electric fields for this purpose. A major factor that inhibits the manipulation of submicrometer particles is the diffraction‐limited spot size of free‐space laser beams. As a result, technologies that can circumvent this limit are highly desirable. This review covers some of the more significant advances in the field, from the earliest attempts at trapping using focused Gaussian beams, to more sophisticated hybrid plasmonic/metamaterial structures. In particular, examples of emerging optical trapping configurations are presented.
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Optical tweezers have been successfully used in the study of colloid science. In most applications people are concerned with the behaviour of a single particle held in the optical tweezers. Recently, the ability of the optical tweezers to simultaneously hold two particles has been used to determine the stability ratio of colloidal dispersion. This new development stimulates the efforts to explore the characteristics of a two-particle system in the optical tweezers.An infinite spherical potential well has been used to estimate the collision frequency for two particles in the optical trap based on a Monte Carlo simulation. In this article, a more reasonable harmonic potential, commonly accepted for the optical tweezers, is adopted in a Monte Carlo simulation of the collision frequency. The effect of hydrodynamic interaction of particles in the trap is also considered. The simulation results based on this improved model show quantitatively that the collision frequency drops down sharply at first and then decreases slowly as the distance between the two particles increases. The simulation also shows how the collision frequency is related to the stiffness of the optical tweezers. 相似文献
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光的力学效应及光阱力的测量 总被引:2,自引:2,他引:0
介绍一个利用光镊技术直观地演示光的力学效应的实验。简要讨论了开设这一实验的背景和目的,给出了光镊原理、实验装置、光阱力的测量方法和实验安排。 相似文献
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A spatial light modulator (SLM) is introduced to an optical manipulation system. The real-time reconfigurable feature of the SLM makes it possible to perform an optical manipulation of microparticles without mechanical movements of optical parts. A liquid crystal SLM incorporated in the system forms a Fresnel zone plate (FZP). The beam spot generated by the FZP is imaged on a sample solution by reduction optics. A microparticle in the sample solution is trapped by the beam and manipulated by changing the addressing position of the FZP onto the SLM from a computer. The nonmechanical optical manipulation of microparticles is demonstrated for the first time. 相似文献
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Optical trapping forces of polystyrene microspheres are analyzed both theoretically and experimentally, and comparisons are
made between the two. Discrepancies are mainly caused by straight-ray approximation for axial trapping, and by trapping-position
vertical displacement due to gravity for transverse trapping. 相似文献
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分别从理论和实验上分析了光纤表面倏逝场强度的分布(z=10 nm, 100 nm, 500 nm,1 000 nm),研究了微米级光纤光镊对微球的操纵。实验中把直径为125 m的普通单模光纤拉制成锥腰直径为2 m的锥形光纤。当光纤通光时,在光纤锥区倏逝场的作用下,直径3 m的聚苯乙烯微球保持平衡状态,并且光纤附近的微球被吸引到光纤表面,以5.3 m /s的速度沿着光束的传播方向运动。这个实验不仅实现了对微球的成功捕获,而且验证了光纤光镊的力学作用。光纤光镊对微球的无接触、无损伤操纵,将在生物传感领域有潜在的应用。 相似文献