Research On Interface Dynamics Process Of Microscopic Soft Matter

The microscopic soft matter generally exists in nature.It is widely applied in industry,environment,biology,micro-nano processing and other fields due to its unique properties and functions.Its broad application prospect has aroused the interest of researchers.At present,the basic physical properties of soft matter are studied by more and more systematic quantitative experiments,theories and numerical simulations.Among them,the study of dynamics is helpful to infer the internal microscopic changes from the external morphological changes.However,there are still many unknown phenomena and potential mechanisms in the dynamics of soft matter,which need to be further explored and studied.In this paper,we experimentally studied two typical dynamic processes of soft matter,namely,the growth dynamics of surface nanobubbles and the evaporation dynamics of emulsion.In the past two decades,the basic physics of surface nanobubbles has been deeply studied,but the growth dynamics of surface nanobubbles is still lack of cognition.In this paper,atomic force microscope(AFM)is carried to study the growth dynamics of surface nanobubbles.We found that the surface nanobubbles will oscillate under a specific temperature difference,and the dynamic process can be divided into three stages: growth after nucleation,oscillation and stability,which indicates that the surface nanobubbles are unstable for a long time.In addition,temperature,as one of the important factors affecting the formation of surface nanobubbles,not only changes the dynamic process of surface nanobubbles,but also affects the time for surface nanobubbles to reach the volume equilibrium and stable state.The analysis shows that the movement of the contact line during the growth and oscillation will contribute to the stability.Therefore,in-depth study of the influence of temperature on the dynamic process will provide a new insight to explain its long lifetime of surface nanobubbles.The evaporation of single component droplet and miscible droplet on solid surface has been paid much attention,but the research on the evaporation dynamics of emulsion on superhydrophobic surface has not been deeply explored.In this paper,a COMS camera with high sensitivity is used to capture the evaporation dynamics of emulsion.The contact radius,contact angle and evaporation rate of emulsions with different concentrations were studied by systematic comparative experiments,and compared with the existing theoretical models.The results show that the evaporation process of emulsion can be divided into three stages: the mixed mode,the constant contact radius(CCR)mode and the spreading of evaporation residue,which are independent of the concentration of hexadecane.In addition,due to the great difference between pure water and hexadecane and emulsifier volatility,the whole evaporation process is still reflected in the evaporation of single component droplets.