Experimental And Theoretical Study On Mechanical Behaviors Of The Liquid Marble And Particle Raft

Liquid marbles and particle rafts are soft matter which are composed of hydrophobic micronanoparticles assembled at the liquid-gas interface.As they possess many peculiar properties,liquid marbles and particle rafts have been widely used in many areas,such as liquid transfer of micro-volume,microfluidic devices,biology,chemistry,crude oil emulsions and mineral flotation.In this work,the mechanical behaviors of liquid marbles and particle rafts are systematically studied.Firstly,a new type of test device is designed to test its mechanical response.Then we use the dimensional analysis,continuum mechanics and surface/interface physics and other knowledge to establish the model and theoretical analysis.The first content is that,we found the liquid marbles and water droplets exhibit different wettability with the decrease of their volumes,and the liquid marbles behaves like solid when the inside liquid volume is very small.When the included liquid is little,the liquid marble is more like a solid film,and exhibits perfect elastoplastic behavior.In this case,the film can be greatly deformed when the pressure is applied,and keep much deformation when the load is removed.Moreover,the film can be arbitrarily carved with specific shapes due to the plastic property.We found that this phenomenon is mainly attributed to the density of surface particles is changed with the reduction of water content.Next,we carried out a comprehensive study of the loading capacity of the particle raft.We designed a special experimental device to measure the force while the slender rod is vertically pressing the water surface and the particle raft,and the force-displacement curve was obtained.In use of this device we also recorded the variation of the morphology of the liquid surface and the particle raft in the process of loading,and it is found that the meniscus is very different in when the rod is piercing the water surface and the particle raft.In addition,the surface tensions of water and particle raft were measured,and we found that there was no difference for these two cases.This fact further stresses that the macroscopic contact angle is an important factor to affect the value of the load.Based on these experimental results,we establish the corresponding mechanical model,and the calculated force-displacement curve is in excellent agreement with the experimental result.