Research About The Effect Of Ion Concentration On Nanobubbles On Polystyrene Surface

Fluid resistance in solid-liquid interface is one of the key factors whenmicro/nano technology applies in the field of life sciences and medicine etc. Thusreducing fluid resistance is very important to micro/nano technology. So studyinghow to reduce the relative motion resistance in solid-liquid interface on micro-nanoscales is one of the hottest research directions in micro/nano technology.Along with the invention of AFM(Atomic Force Microscope) and its applicationin micro-nano technology research, researchers found nanobubbles on hydrophobicsurface in aqueous solution. Surface nanobubbles are considered an important factoraffecting fluid resistance in solid-liquid interface. So studying the formation andproperties of nanobubbles in solid-liquid interface is one of the main directions whenresearching on reducing the fluid resistance in micro-nano pipeline.There are many factors affecting the formation and properties of nanobubbles,such as wettability and roughness of sample, temperature, ion concentration, PHvalue of solution and the applied electric field. All these factors will have an effecton the formation, shape, size, distribution and stability of the nanobubbles.Thisdissertation mainly study how ion concentration have effect on the formation andproperties of nanobubbles. The main research content includes the following threeaspects:Firstly, establishing the electrowetting tension model to study the effect ofsurface charge on the contact angle of surface nanobubbles.The electrowettingtension induced by surface charge is studied and introduced into the Young’sEquation to analyze the change of contact angle of nanobubble. The results show thata larger magnitude of surface charge density of both the solid-liquid interface andair-liquid interface leads to a larger magnitude of electrowetting tension, and thenleads to a larger change of contact angle. In addition, the value of electrowettingtension is negative, so the existence of surface charge causes the increasing ofcontact angle of nanobubble. Furthermore, a larger ion concentration of nanobubbleleads to a larger magnitude of electrowetting tension and then a larger change ofcontact angle.Secondly, using AFM to research how different ion concentration affects thesize and shape of nanobubbles on the polystyrene surface. According to analyzingthe AFM images of nanobubbles on the polystyrene surface in NaCl solution withdifferent concentration, we found percentage of nanobubbles basically remainedunchanged, the average diameter of nanobubbles will increased with the increase of solution concentration, and the number of nanobubbles decreased with the increaseof solution concentration. The influence ion concentration on surface nanobubblesswitches to the influence on electric field distribution of solution. According toanalyzing the change of electric field, we got the relationship between ionconcentration and the shape and size of surface nanobubblesFinally, using AFM to research the stability of nanobubbles on polystyrenesurface.The results show that surface nanobubbles are kinetic stability and the solid-liquid interface is airtight. Through the force modulation experiment further provedthat nanobubbles have surface layer. Ion as impurity in the solution played a key rolein the formation of impurities film. The kinetic stability of surface nanobubbles duesto the impurities film.The impurities film makes the diffusion resistance of gas-liquidinterface huge.In conclusion, this paper researches the effect of ion concentration on theformation and properties of nanobubbles on polystyrene surface, provides a newdirection and new ideas for the study of reducing fluid resistance of micro-nanopipeline.