Study Methods Of Induction Of Fluid Shear Stress Through Precise Manipulations Of Microspheres With Optical Tweezers

The mechanical properties of cel s have an important influence on cell growth,deformation,and cell self-regulatory functions.At present,the mechanical properties of cells can be studied through a variety of micro-manipulation techniques study of cell mechanic a l properties,such as micropipette method,atomic force microscope,magnetic bead torsion method,substrate strain technology,etc.Among the many mechanical forces that cel s receive,fluid shear force is one of the main stress loading forms that cel s in the human body are subjected to under physiological conditions.It is of great significance to study the response of cel s to shear stress to reveal the pathogenesis of related diseases(osteoporosis,atheroscleros is,etc.)and explore more effective treatment methods.Traditional cell shear stress loading experimental techniques based on flow cel s mostly use cell populations as experimental objects and cannot reflect the heterogeneity between cel s.Therefore,based on single-cell shear force loading technology-microfluidic technology has gradually developed.The loading technology can accurately control the fluid,achieve automated analysis and other functions.But the fluid flow is a single way(need to specifically design a different chip to change the fluid flow method),and the limitations of the manufacturing process.Aiming at the limitations of microfluidic technology,this paper proposes a novel microfluidic shear force loading method for precise control of aperture microspheres.This method utilizes an optical tweezer to manipulate the microspheres to perform translational movements in the vicinity of the cel s,and causing fluid flow in a local area to produce shearing forces with adjustable and controlled modes of action.This method integrates automatic control,machine vision,and optical tweezers.The specific research content mainly includes the following aspects:(1)The optical aperture accurately controls the microsphere motion algorithm.Based on the kinetic model of the microspheres captured by the aperture,a closed-loop control algorit hm is implemented.The position information of the microspheres is fed back in real time in combination with the image processing technology.This solution solves the problems caused by excessive speed or fluid interference during the motion of the aperture-controlled microspheres.The problem of microsphere escaping solved the precise control of microspheres by the aperture.(2)Image processing algorithms for acquiring microsphere position and radius information.Aiming at the problem of feedback of position information of microspheres during the movement of the iris-controlled microspheres,calibration problem of optical trap stiffness,and verification of microfluidic shear force in experiments,the OpenCV open source project library is used to propose the position and radius of microspheres based on differe nt il umination environments.Information acquisition algorithm for image processing.(3)Theoretical solution of the magnitude of microfluidic shear force.Aiming at the theoretical solution to the shear force caused by fluid flow in microspheres,a theoretica l solution model of the method is proposed based on the Stokes flow theory.The theoretical value of the shear stress of a cell is calculated by solving the approximate solution of the theoretica l model.(4)Experimental verification of the proposed method.The results show that the micro-fluidic shear force loading method of the diaphragm precisely controlling the movement of the microspheres can accurately and suffice the cells with adjustable and controllable shearing force.It has the advantages of simple operation,good controllability and high precision.