We propose a light-sheet fluorescence microscopy imaging method based on active optical manipulation with linear laser optical tweezers. In this imaging method, a column lens is utilized to generate an excitation light sheet, and a linear laser light tweezer is adopted to capture and precisely control the rotation of the experimental object. The linear laser optical tweezers are used to capture and precisely control the rotation of the experimental object. The plane of the light sheet is perpendicular to the rotational plane of the experimental object, and the rotation of the experimental object at different angles can be controlled to realize the light sheet on the experimental object layer. The light sheet is perpendicular to the rotational plane of the subject. Most importantly, compared to traditional microscopy methods, this solution directly manipulates and observes the experimental object, which reduces the risk of the object changing position in the sample container. It reduces the uncertainty and error of image acquisition and reconstruction caused by the change of the position of the experimental object in the sample container.
In order to obtain the fine structure of biological tissues and living cells, microscopic imaging techniques are required to have tomographic capabilities. We propose a dynamic speckle fluorescence illumination microsystem based on active light manipulation, which uses the dynamically changing speckle pattern to illuminate the sample to be measured in full field, rotates the sample to be measured through linear laser tweezers, and obtains a three-dimensional fluorescence tomography image by extracting the fluorescence signal that changes sharply in the focal plane. The system changes the previous passive observation to active observation, and realizes the acquisition of three-dimensional structural chromatographic images with high temporal and spatial resolution without affecting the nature of the cells themselves and their environment, and the long-term dynamic quantitative monitoring of their life activity processes.
Optical lattices are generated by superposition of a set of plane waves, and have been widely used in the quantum information, atomic cooling, condensed-matter physics, optical sectioning imaging and lithography. A periodic two-dimensional optical lattices, weakly confined in its propagation direction, can be used as an excite source to perform multifocal scanning. By controlling the angles of superimposed plane waves, the propagation direction of 2D optical lattices can be adjusted to achieve 2D optical lattices with equal obliquity. In this paper, we have firstly investigated the basic generation principles of the square 2D optical lattices with good symmetry. The influence of numerical aperture, and other parameters on the basic parameters of fundamental optical lattices, had been analyzed with the finite element method. Based on these, the basic parameters of 2D inclined lattices had been further analyzed. The research results will provide a theoretical basis for future applications of optical lattices in optical sectioning imaging.
The precise capture and control of nanoparticles by using optical tweezers has become a hot research topic in the field of nano-optics. Especially, the pulsed tweezers have been robustly used to manipulate the nanoparticles because of the high peak power, compared with the continuous optical tweezers. It is still not yet clear that the difference of light scattering by the nanoparticle in the pulsed and continuous optical tweezers, as well as different dispersion processes. In this work, we constructed a finite element model of a nanoparticle and calculated the light scattering and dispersion by the particle irradiated by the pulsed (femtosecond and picosecond lasers) and continuous trapping beams with the same average power, respectively. Both pulsed and continuous optical tweezers were defined as the highly focused, Gaussian distributed, radial polarized and spherical electromagnetic field. Nanoparticles were chosen to be golden particles. We discussed the electromagnetic field evolution, the particle size effects on the energy loss, and the near field distribution. The simulation results offer the significant information for choosing the best laser source for efficient manipulations and other related fields.
Optical tweezers, capable of precise manipulations on micron/nano particles, can be greatly used to study the biophysics of cells and the interaction between biological molecules. The mechanical properties of cells are inherent properties of a cell, which could be measured by using a probe navigated by optical tweezers instead of the expensive atomic force microscopy (AFM). However, it is still a great challenge to precisely measure the cell mechanical properties because of the cell deformation highly depending on the contact mechanics of the probe. In this study, the finite element analysis (FEA) method was firstly employed to simulate the cell deformation with the spherical probe manipulated by optical tweezers. Then, cell mechanical responses to the contact force were discussed to investigate the probe radius effects on mechanical properties of cells. Traditionally, Young’s modulus could be calculated in Hertz model with the cell deformation. It was found that the measured results of Young's modulus varied as the probe radius, although the preset mechanical property in the cell model was kept the same. When the contact force was less than 100 pN, the measured Young's modulus of the cell decreased with the increase of the probe radius, and gradually tended to be constant at the state of the maximum deformation. We proposed an algebra method to optimize the Young’s modulus fit to the preset material parameter. This may provide a precise way of predicting the mechanical properties of biological cell manipulated by contact probes.
We propose a fiber optical cell catapult that is bird beak-shaped fiber cone optical tweezers that trap cells, then push them to the fiber tip via the evanescent fields on the side surface of the fiber cone, and finally eject them in a particular direction. The intensity distribution of the light field and the optical force of the fiber catapult are calculated by the finite element method. Moreover, an experimental study of the fiber catapult is given using yeast cells.
Stitching is used to reduce dry-core and reinforce T-joint structure. However, it might cause new types of flaws, especially submillimeter flaws. In this paper, new approaches including micro-VT, lock-in micro-LLT and micro-LST based on both lock-in and pulse methods are used to detect submillimeter flaws in stitched CFRP. A comparison of laser excitation thermography and micro-VT on micro-porosities is conducted. Micro-CT is used to validate the infrared results. Then, a finite element analysis (FEA) is performed. The geometrical model needed for finite element discretization was developed from micro-CT measurements. The model is validated for the experimental results. Finally a comprehensive experimental and simulation comparison of micro-LLT and micro-LST based on both lock-in and pulse methods is conducted.
We analyzed the temporal responses of biological cells in the jumping optical tweezers for tugging, wiggling, and stretching the cells in the time-sharing regime with the finite-element method. We showed that the jumping of local stress and local strain is independently omnipresent on the recovery time of the viscoelastic material and the jumping frequency of the load. We demonstrated that the elongation of a three-dimensional (3-D) viscoelastic object under a jumping load cannot be evaluated using the one-dimensional spring-dashpot material model without considering its 3-D structure.
We analyzed the temporal responses of biological cells in the jumping and vibrating optical tweezers for tugging, wiggling and stretching the cells with the finite element method. Some new concepts were established, which might be investigated in the future experiments, such as the jumping of local stress and local strain, independently on the recovery time of the viscoelastic material and on the jumping frequency, the energy dissipation in the hysteresis cycles, the cytoplasm fluid field and its interaction with the cell membrane. The cell was modeled with full 3D structure and viscoelastic continuum materials.
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