Experimental Investigation On Promoting Oil Droplet Using Surface Acoustic Wave On Non-piezoelectric Substrate

In this paper,the surface acoustic wave technology is elaborated and introduced in detail.The various applications and technical features of surface acoustic wave in the field of microfluidic driving are studied.Then,the theoretical analysis of the materials required for this experiment is made and the piezoelectric wafer is selected as the transducer,the sound waves excited by the transducer can be propagated on the curved surface.For the target application field of this paper,the road traffic lubrication system is selected as the substrate.Combining with the classical theory of fluid mechanics,the Navier-Stocks equation deduces the theoretical model of the Lamb wave-driven oil droplets,theoretically simulates the force of the microfluids,and derives three main factors affecting the movement of the oil droplets.Finally,based on the theoretical model,this paper designs the experimental scheme of Lamb wave to promote oil droplets,and uses the method of controlling variables to realize the experimental research on oil droplet movement.Experiments were conducted on the wettability of oil droplets on the surface of different non-piezoelectric substrates to make a supplement for the experiment of surface acoustic waves driving oil droplets.The results show that the displacement of the Lamb wave pushing the oil droplets will be affected by three important factors: acoustic flow force,gravity,and the inclination angle of the substrate.Each factor will change the displacement of the oil droplet movement;when the excitation voltage and the oil droplet volume is fixed,the motion displacement of the Lamb wave driven oil droplet increases with the increase of the substrate inclination angle,and this feature is most obvious when the oil droplet volume is 10?L;the displacement of the oil droplet within 30 s and the final displacement of the oil droplet also has this conclusion,which also shows that as the inclination of the substrate increases,the average velocity of the oil droplet movement also accelerates.When the substrate inclination angle and the oil droplet volume are constant,the oil droplet displacement increases with the increase of the excitation voltage,and the oil droplet displacement on the slope is larger than the oil droplet displacement on the plane;when the substrate inclination angle and the excitation voltage are constant,the volume of the oil droplet is larger.The larger the driving force of the Lamb wave,the larger the displacement of the oil movement.The oil droplets with a volume of 30?L are more affected,and the displacement is significantly larger than 10?L and 20?L oil droplets.The contact angle of oil droplets on the surface of different substrates generally shows a downward trend,and as time increases,the contact angle will gradually tend to a smaller angle interval.On a horizontal substrate,as the volume of oil droplets increases,the oil droplets change in different angles.The contact angles on the substrate all showed a decreasing trend;the rate of change of the contact angle of the oil droplets during the initial stage of attachment to the horizontal substrate was large.With the increase of time,the rate of change of the contact angle of the oil droplets on different substrates within 10 s.shows a gradual decreasing trend;with the increase of time,the rate of change of the advancing angle and receding angle of the oil droplets on the inclined substrate gradually decreases within 10 s,and the spreading speed of the oil droplets on the inclined substrate gradually decreases;The spread diameter of the oil droplets on the different substrates increases with time,and the spread diameter of the oil droplets on the inclined substrate is larger than the spread diameter of the oil droplets on the horizontal substrate.