Experimental Study On The Mechanism Of Droplet Evaporation On Deformed Surface Regulated By Magnetic Field

With the improvement of technological processes and the development of smart materials,flexible materials represented by magnetorheology materials have a wide range of applications in bioengineering,electronic instruments,mechanical seals and other fields.Magnetic elastomer material is a kind of magnetorheological material,which has the advantages of magnetic particles not easy to settle,small Young’s modulus and easy deformation,etc.Magnetic elastomer material also has been used in the process of droplet transport without energy input.Droplet evaporation is a ubiquitous physical phenomenon in nature.Studying the characteristics of droplet evaporation on flexible curved surfaces is of great significance in the fields of inkjet printing and fog collection.The process of droplet evaporation on the surface of magnetic elastomers has not been studied yet.Surface shape is an easily overlooked factor during the heat transfer process of evaporation.In this paper,the mechanism of droplet evaporation on flexible and flexible deformable surfaces is investigated experimentally.First,Polydimethylsiloxane(PDMS)surfaces with different curing ratios were prepared,and the experimental mechanism of sessile droplets evaporation on the PDMS surface was carried out.The study showed that the droplets evaporated in a constant contact line(CCR)mode on a PDMS surface with a solidification ratio of 40 to 1,and evap orated mainly in a MIX mode on a surface of 80 to 1.With the increase of the solidification ratio,th e evaporation rate increased and the total evaporation time is shortened,so the substrate softens promote evaporation process.Secondly,a magnetic-soft elastomer surface,which can be controlled and stably deformed by the magnetic field force was prepared,and the sessile droplet evaporation experiment was carried out on this surface.The study found that the droplets evaporated mainly in the CCR mo de on the surface of the magnetic-soft elastomer.Compared with the PDMS surface,the dynamic behavior of the droplets evaporated in the CCR mode on the deformation surface of the magnetic-soft elastomer was more obvious.The reason was that the bulges on the surface restricted the movement of three-phase contact lines.Finally,the finite element analysis software COMSOL Multiphysics was used to construct the mathematical model of the spherical permanent magnet in the infinite air domain,and the magnetic field distribution of the permanent magnet in space was calculated.The spatial magnetic field strength along the magnetization direction of the permanent magnet was measured using a Teslameter.It was found that the experimental measurement value was not much different from the simulated value.The deformation of the surface convexity was compared with the surface convexity photographed in the experiment.It was found that when the distance between the permanent magnet magnetic ball and the surface of the magnet ic-soft elastomer is 4mm,the maximum convexity value obtained by the experiment and simulation calculation differs by 7.13%.In this paper,the controllable deformation surface under magnetic field was realized for the first time to control droplet evaporation,which enriches the experimental research on the mechanism of sessile droplet evaporation on curved surfaces.