| Liquid viscosity coefficient is an important parameter to characterize the ability of liquid to resist deformation,which plays an important role in material science research,engineering technology and biomedical field.With the rapid development of detection technology in biomedicine,material science and other fields,new requirements are put forward for the speed and accuracy of detection technology.Especially in the measurement of biomedical samples,it is necessary to strictly control the amount of measured samples.Therefore,it is a very meaningful and worthy of study to study a fast,high-precision liquid viscosity measurement method with less sample consumption to meet the development needs of various industries.In order to solve the pain points in the above-mentioned industry measurement methods,this topic mainly focuses on the optical tweezers capture method,using the four-quadrant photodetector(QPD)with faster detection speed to measure the motion data of the lightcaptured microbeads,and the liquid viscosity information is obtained by calculation.In this paper,the appropriate QPD photodiode is selected through investigation,the QPD detection circuit is designed and manufactured,the reasonable mechanical structure parts are designed and processed,the control and measurement program of QPD is designed,and the COMSOL simulation and experimental calibration of QPD are carried out.In this paper,an optical tweezers system was successfully built and the capture and manipulation of microbeads were completed.The optical trap stiffness calibration of optical tweezers was realized by measuring the motion data of microbeads.In this paper,the relationship between the measurement signal and the liquid viscosity is calibrated by capturing and measuring the microbeads under different standard viscosity solutions,and the measurement of liquid viscosity is preliminarily realized.The main contents of this paper are as follows :The first chapter mainly analyzes the methods and shortcomings of measuring liquid viscosity at home and abroad,and obtains the development trend of measurement methods and the new needs of various industries for measurement methods.Based on the above analysis,the research content,purpose and significance of this topic are proposed.The second chapter mainly describes the overall scheme and basic principle of the liquid viscosity measurement system,including the basic principle of QPD,the basic principle of optical tweezers,the basic principle of optical trap stiffness and liquid viscosity measurement.It also includes the selection of main components of the equipment,some necessary mechanical structure and processing.The third chapter mainly focuses on the function realization and software design of QPD,including the basic information of QPD photodiode,the design and manufacture of QPD peripheral circuit,signal acquisition,design control and measurement software.The fourth chapter mainly introduces some related experiments of QPD in this subject,including QPD calibration experiment and simulation,liquid refractive index measurement experiment and surface topography measurement experiment to verify QPD function.The fifth chapter mainly introduces the related experiments of the liquid viscosity measurement part of this topic,including the optical tweezers light capture beads and optical trap stiffness calibration experiments,liquid viscosity measurement experiments.The sixth chapter summarizes and summarizes the full text,and looks forward to the future development and the research work of this topic. |
