A Particle Size Detection Method Based on Optical Trapping

Abstract

The invention provides a particle diameter detection method based on optical trapping. The method comprises the following steps of analyzing the power spectrum of displacement of particles trapped by an optical trap, wherein a signal comprises Lorentz distribution corresponding to limited Brownian movement and peak of forced movement; according to the area of the peak relative to the Lorentz distribution and the height of the peak, inverting the voltage proportion coefficient of a micro particle in the optical trap when the micro particle is detected by a detector, and according to the micro particle diameter with the standard size, measuring the ratio of coefficient of viscosity to temperature; acquiring the temperature in the optical trap according to the relationship between the coefficient of viscosity and the temperature; collecting a forced movement signal of a to-be-detected micro particle in the optical trap, and then calibrating the voltage proportion coefficient of the detector to the micro particle by utilizing the power spectrum; and acquiring the diffusion coefficient by the power spectrum of thermal noise, and determining the particle radius according to the temperature, the coefficient of viscosity as well as Stokes-Einstein relation of standard micro particle measurement. The method can be used for detecting the particle diameter of each particle in an experiment environment, that is, the method can be used for detecting the particle diameter with high precision in situ.

Description

technical field [0001] The invention belongs to the technical fields of particle diameter detection, single molecule measurement method and optical micro-manipulation, and in particular relates to a particle diameter detection method based on optical trapping. Background technique [0002] Particle size detection is widely used in many fields, such as particle size measurement in various powder industries, particle size measurement in suspension liquid medicine, and cell size measurement. At present, there are many technical methods widely used to measure particle size in large quantities, such as sieve analysis method, sedimentation balance method, electrical resistance method and laser scattering method. [0003] In the study of the mechanical properties of biological macromolecules, when optical tweezers or other measurement tools are used, the characteristic is that the purpose of detecting the mechanical properties of single molecules is achieved by coupling macromolecu...

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