Study On Dynamic Mechanical Properties Of Liquid Marbles For Microfluidic Manipulation

Liquid marble are soft substances formed by wrapping liquid with hydrophobic particles with a particle size of micrometers or nanometers.Due to their excellent physical properties such as non-wetting,high elasticity,low friction,slow evaporation,and external environment interaction,they have been widely studied in recent years and applied to practical engineering as miniature reactors,sensors,and digital microfluidic platforms.The means to precisely control the movement of liquid marbles is becoming more and more mature,and the research on the dynamic mechanical properties of liquid marbles is helpful to better guide practical applications.In view of the current research on the elastic mechanics of liquid marbles mainly under quasi-static conditions and the lack of systematic theoretical discussion and experimental proof of kinematic friction,this paper takes the elastic properties of liquid marbles under dynamic pressure and kinematic friction on the solid plane as the research objects,and proposes an elastic force measurement system based on a largesize cantilever beam with laser interference principle and a friction measurement method based on image processing.The main research work of this paper is as follows:1.Taking the microfluidic manipulation as the research background,theoretically analyze the dynamic mechanical properties of liquid marbles.Establish the geometric model of liquid marbles applicable to different compression stages and derive the theoretical equation of elastic force.The mechanism of the frictional resistance on the solid plane of the liquid marble is studied,and the influencing factors of frictional resistance are analyzed from the energy point of view.Measure the geometric parameters of liquid marbles of different volumes and materials,compare them with the droplets and analyze the morphological characteristics.2.Completed the design and construction of the laser measurement module,compression process module and operation control host computer of the liquid marble elastic force measurement device under dynamic load.Analyze the research object and the accuracy requirements of the measurement,design the dimensional parameters of the cantilever beam and carry out the stiffness calibration.Design the motion friction measurement device of liquid marbles on the solid plane,use a high-speed camera to collect the movement trajectory of the liquid marble on the solid plane.Two image processing algorithms based on Hough transform and Gaussian mixture model are proposed to extract the position coordinates of the liquid marble in the image sequence.3.Measure the elastic force and movement friction of liquid marbles.Analyze the influence of volume,effective surface tension,physical properties of the particles and the viscosity of the inner core liquid on the maximum compression that the liquid marble can withstand,the maximum elastic force generated when it ruptures,and the mechanism of motion friction.Repeated experiments were performed to verify the reliability of the measurement system.The synthetic relative standard uncertainties of the experimental results were 2.039% and 2.567%,respectively.