Study On The Method Of Viscosity Measurement For A Small-volume Liquid Based On The Shear Motion Of The Rigid Rod

Viscosity is a physical property of the liquid that produces a resistance when an object moves in the liquid.Measurements of viscosity of small-volume samples are of high importance in analytical chemistry,bio-engineering,bioengineering,micro-manufacturing,etc.Viscosity plays a vital role in scientific research and engineering implementation and viscosity measuring is of great significance.In this paper,the advantages and disadvantages of the existing methods for measuring the viscosity of trace liquid are analyzed.Based on the cantilever beam method for the measurement of a small-volume liquid viscosity,a new viscosity measurement based on shearing motion of the rigid rod is proposed.The new method aims at solving the problem of small measurement range.Firstly,the basic principle of the measurement of liquid viscosity is analyzed,and the problem of different adsorption heights due to capillary phenomenon in different liquid and rigid rod probe parts by differential method is solved,then it is established that the relationship between liquid viscosity and damping factor.Finally,a viscosity measuring device requiring a small-volume sample is built to measure the viscosity.The software is designed to form an integrated automatic measuring system,and it is compatible with the new viscosity measuring device.It can measure the viscosity of the liquid automatically as while as the software starts.Through the verification experiment,the error of liquid viscosity measurement is compared and analyzed,which proves that the method of the viscosity measurement requiring the small-volume samples in this paper is reliable and effective.The main work and innovation of this paper are as follows.1.The methods of viscosity measurement requiring the small-volume liquid at home and abroad are introduced in detail,especially the method of viscosity measurement based on cantilever beam.In order to solve the problem of small measurement range of viscosity in the process of measurement,a novel viscosity measurement method based on the shear motion of the rigid rod is proposed,which can enlarge the range of viscosity measurement.2.The principle of viscosity measurement based on the shear motion of the rigid rod is analyzed and introduced.The relationship between liquid viscosity and damping factor of the system is established.In order to eliminate the influence of surface tension on the damping factor,the damping factor of the system is substituted by a difference method.The structure of viscosity measurement device is designed and the structural parts are selected.The finite element analysis software is used to simulate the shear motion of the probe part of the rigid rod in liquid.The magnitude of the shear stress on the probe surface is analyzed.3.The software design of viscosity measurement system is realized.The calibration and verification experiments of the novel viscosity measuring device used for small-volume liquid are designed.The Feasibility experiments,calibration experiments and verification experiments are carried out respectively,and the errors are analyzed after the experiments.The calibration result shows that the range of the viscosity measurement is 10~750mPa.s,the maximum value of the relative error is 8.3%.The uncertainty analysis indicates high accuracy and sensitivity.The effects of vessel width,density,and temperature on the results are also investigated.The repeatability and sensitivity of the measurement reaches a higher level.