Studying On The Optical Tweezers Technique And Its Application In Optically Driven Micromachine Motors

This dissertation is devoted to the study of the application of optical tweezers on life sciences and micromachine field, aiming at the solution of problems such as optical micromanipulation of micrometer-sized biological particles and optically driven micromachine, etc. The dissertation is composed of two parts: Firstly, aiming at a number of problems needed to resolve about trapping, manipulating biological cell and macromolecule applied in life sciences field, theoretical calculation and simulation analysis of the optical trapping force of laser microbeam acting on Mie particle were studied. Based on our research, a single-beam optical tweezers experiment system was established; Secondly, aiming at a number of problems of rotation mechanism and realizing technique of optically driven micromachine, we have done some theoretical calculation and simulation analysis about optical torque based on optically driven birefringent crystal particle, and established basic optical rotation experiment device, and designed experiment system of micromachine motor driven by double optical trap further.A cell is a basic unit of life structure and function. The characteristics of optical tweezers applied in manipulating micrometer-sized particles are suitable for the investigation of cell and subcell exactly. Optical tweezers have specific characteristics of accurate positioning and choosing a single particle. Optical tweezers can manipulate alive biological samples in a non-contacting and nondestructive way. The force of piconewton order of optical tweezers is exactly suitable for the investigation of cell and subcell structure. In the dissertation the following contents were studied:We use different calculating models of theory about the optical trapping force of different sized particles: when particle size is much larger than optical wavelength (such particle is named Mie particle), ray optics model is utilized to calculate axial optical trapping force and transverse optical trapping force of Mie particle; when particle size is in the range of mesoscopic scale, electromagnetism model with Debye integral expression is utilized to deduce optical trapping force of mesoscopic particle. Using Matlab software, we carried out the numerical simulation on axial and transverse optical trapping force of spherical Mie particle acted by strongly divergent optical field and strongly convergent optical field near focus in laser microbeam respectively. Based on the simulated results, we studied the different parameter of experiment system effecting on optical trap action. According to these, we designed a single-beam optical tweezers experiment system and a double trap optical tweezers experiment system, and demonstrated design basis of each section of the systems. According to the demonstration result, we established a single-beam optical tweezers experiment system, and measured optical trapping force of a polystyrene sphere, a microzyme cell, a human red cell and a cell in a capillary using the experiment system, and verified the optical trapping force is in piconewton order.Optical rotation can achieve angular manipulation of particles. Rotating particles need beam possessing spin angular momentum or orbital angular momentum, and particles possessing birefringent characteristic or special shape. We studied these problems as following:Theoretical analysis about interactional process of polarized beam and birefringent crystal particle was done, and optical rotation elements induced by transfer of spin angular momentum and orbital angular momentum toward birefringent crystal particle were discussed respectively. When the parameters were given, numerical results about optical torque were obtained. Based on these, we discussed the effects of radius size of birefringent crystal particle and beam axis to optical torque. We designed an optical rotation experiment device, and carried out optical rotation experimental measure to two birefringent crystal particles (SiO2 particles and CaCO3 particles) in this experiment device. The relation curves between rotation frequency of two particles and laser power were obtained.On the basis of optical tweezers and optical rotation experiment, we put forward the idea of micromachine motor driven by double optical trap. Double optical trap is realized through single optical trap and a single-mode fiber optical trap. Using the action of polarized beam on birefringent crystal particle, optical torque can be transferred to birefringent crystal particle. The rotation of birefringent crystal particle is caused by circular polarized beam. When some gear-shaped micromachine rotors were placed around this rotated birefringent crystal particle, the moving of surrounding liquid was driven by the rotation of birefringent crystal particle, thus rotation of micromachine was driven. We also designed several single-mode fiber optical tweezers experiment devices for optical rotation and several gear-shaped micromachine rotors prepared optically.