Photothermal Evaporation And Peeling Kinetic Mechanism Of Liquid Marble Interface

Nanomaterials are widely used in solar energy conversion research due to their excellent photothermal properties.Nanofluid solar photothermal systems have good prospects for applications in water treatment,steam power generation,and steam sterilization.However,the irregular collision and agglomeration of particles within the fluid severely limit their optical absorption and thermal conversion performance.In addition,the particles have strong adsorption energy at the fluid interface,making it challenging to peel the particles from the interface.In this paper,the liquid marbles formed by assembling micro and nano particles on the droplet surface are used as the research object,and a new idea of enhanced evaporation from the photothermal boundary layer is proposed to systematically study the regulation mechanism of the photothermal interface and its photothermal evaporation properties on different substrates.In terms of stripping kinetics,two types of fast impact stripping methods based on liquid pool and liquid film are proposed to reveal the kinetic stripping mechanism of the particle layer from different physical levels by using mechanical analysis,energy analysis and dimensionless analysis.The main studies are as follows:The photothermal nanoparticles were assembled on the surface of liquid droplets to construct a three-dimensional photothermal boundary layer,and the photothermal evaporation of liquid marbles was studied experimentally on a solid substrate.The results show the important role of surface roughness in the photothermal conversion,and two evaporation dynamic features,dome collapse and constant spherical collapse,are found.The finite element method simulation further demonstrates that the rough structure possesses stronger performance in light absorption and heat generation.Based on the experimental study of the photothermal evaporation of liquid marbles on the liquid surface,it is found that the liquid marbles always maintain a slightly depressed initial spherical state during the long time evaporation process,and the analysis shows that this is due to the particle layer hindering the evaporation of the internal liquid and the hindering effect increases with the increase of external humidity.In order to enhance the photothermal conversion of the liquid marbles,glycerol-water solution with low specific heat capacity was introduced inside them.Compared with the photothermal evaporation of the liquid pool surface without and with pure water liquid marbles,the evaporation rate of the liquid pool with the addition of glycerolwater liquid marbles increased by 1.44 and 1.20 times,respectively,showing a better photothermal evaporation enhancement ability.The dynamic impact peeling method of liquid marbles based on liquid pool is innovatively proposed,and the kinetic characteristics of different liquid marbles during rapid dynamic impact on liquid pool are systematically studied,revealing two dynamic modes of bouncing and peeling.The experiment found that there were significant differences in the particle layer rupture time of different liquid marbles dropped from the same height,mainly due to the coupling effect of impact pressure and surface tension.Theoretical derivation found that the dimensionless Weber number can be used to characterize the interaction between the two effects.Based on this,the dynamic mode regimes of different liquid marbles were obtained,and three boundary thresholds based on the Weber number were established for different regimes of the liquid marbles,which were approximately 19.22,17.08,and 10.68,respectively.The differences in the threshold values between different liquid marbles were due to differences in their effective surface tension and the surface particle attraction force.A method to achieve viscous peeling of particles on the surface of liquid marbles using a separate soap film is proposed.and it is experimentally verified that complete peeling of the particle layer can be achieved by the rapid dynamic impact of liquid marbles on the soap film,and three dynamic modes of bouncing,peeling and passing through the liquid film are observed.This method achieves the transition between the three dynamic modes within a controllable range by adjusting the diameter of the liquid marbles and the falling height.The viscous peeling of particles on the droplet surface is achieved through dynamic contact transfer between the liquid film,the particle crust,and the droplet.Thermodynamic analysis reveals that particle layer peeling depends on the energy competition between kinetic energy(E_k).surface energy increment(E_s),and viscous dissipation(E_d).When E_s<E_k<E_s+E_d,particle peeling can be achieved by the liquid marble striking the liquid film,and two theoretical thresholds of the peeling mode are derived.Dimensionless analysis and mechanical analysis further reveal the regularity of particle viscous peeling and the microscopic mechanism of particle layer rupture.The effect of particle size effect on soap film peeling and dynamic processes was further investigated.The experiments show that by controlling the falling height and droplet volume,the rapid dynamic characteristics of liquid marbles include four modes of coalescence,bouncing,peeling,or tunneling through the film.By analyzing the motion trajectories and velocity changes of three liquid marbles falling from different heights,it was found that the differences in motion characteristics between different modes are mainly related to kinetic energy and the viscoelasticity of the liquid film.The experiment found that the peeling regimes can be selectively controlled by adjusting the particle size,and the assembly of smaller particles can form a wider peeling area.By adsorption free energy analysis and Weber number analysis,it was found that the larger effective surface tension and smaller adsorption energy possessed by smaller particles wrapped on the liquid marbles are the main reasons for the expansion of the peeling regime.Combining the experiments and energy analysis,the separation regimes of different liquid marbles were obtained,and the reason why smaller stable particles can make the peeling regime wider was revealed.Based on the theoretical peeling threshold,active regulation of the range of the peeling area can be achieved by adjusting the size of the particles.The new idea of liquid marbles photothermal boundary layer evaporation and the new method of interfacial particle layer dynamic peeling proposed in this paper are distinctive and pioneering.It not only expands the basic research on the thermal and mechanical aspects of colloidal interfaces,but also provides scientific basis and theoretical guidance for the application of liquid marbles,which is of great scientific significance and application value to the scientific research on colloidal interfaces.