Research On Surface Tension Measurement Method And Application Of Liquid Droplet Based On Ultrasonic Radiation Force

The interfacial tension of a liquid(IFT)is the contraction force acting at the interface of a unit length of liquid,when one of the two phases forming the interface is a gas phase,then the interfacial tension can be referred to as surface tension.IFT plays an important role in industrial,biomedical and synthetic chemical applications.IFT measurements are required in industrial processes such as evaluating detergent quality,developing new coating formulations,and assisting in the development of third oil recovery(EOR)technology for petroleum.The traditional measurement methods for surface tension are dynamic tension measurement and static tension measurement.The more representative static surface tension measurement methods are Du Noüy-pull ring method,bubble pressure method,etc.;the representative measurement methods for dynamic surface tension are oscillatory jet method,etc.The physical properties of biological fluids such as blood,urine and sweat often reflect the health condition of the body,and IFT measurement of biological fluids can effectively achieve early diagnosis of diseases.However,measuring IFT usually requires sufficient amount of the liquid to be measured to wet the probe or contain the air bubbles,or requires slow drops to measure the shape and mass data.A surface tension measurement scheme based on surface acoustic wave(SAW)for microsample liquids is proposed in this paper to address the characteristics of small sample size,high testing demand and time-sensitive detection of biological fluids.The tension measurement scheme is inspired by the droplet shape based sessile droplet method and suspension droplet method,and the shape data of the vibrational deformation generated by the droplet when SAW acts on the droplet is calculated by using the Taylor deformation equation for its IFT.Due to the difference in IFT of different droplets,the acoustic streaming-induced deformation inside the droplet when it interacts with SAW will also be different for the purpose of tension measurement.We chose a interdigital transducer(IDT)to generate SAW to induce acoustic flow,and performed finite element simulations of the physical fields on the surface of the IDTs and inside the droplet,respectively.The SAW generated by this device is used to control the droplet deformation under a high-speed image acquisition device,and the image data of the droplet deformation are collected and quantified to calculate the final IFT of the liquid to be measured using Taylor's deformation equation.In this experiment,the surface tension coefficient values of 68.369 N/m for deionized water and 60.44 N/m for glycerol were measured by the SAW method,and the error margin was only ±5%(25 °C)compared with 72.75 N/m and 63 N/m for the suspended droplet method,which verified the accuracy of the SAW measurement method.L)and a short measurement time(less than 3 min)to obtain more accurate results.In order to verify the potential of the SAW method in the field of life and health,plasma IFT measurements were performed on healthy mice and diabetic mice,and the plasma IFT in normal mice was around 72.82 N/m,while the plasma IFT in diabetic mice was around 56.23 N/m.The results successfully demonstrated the sensitivity and accuracy of IFT measurements in screening diabetic plasma.The SAW measurement method for IFT has the advantages of low sample volume required,low cost,simple mechanism and fast measurement speed,and has a broad application in industrial production and life and health fields.