Janus颗粒撞击气泡的行为特征

Behavior characteristics of Janus particles impacting bubbles

为更好地在相变传热中应用双亲性Janus颗粒,用铜球制备了亲水-超疏水Janus颗粒,其粒径为1.0 mm,气泡直径为3.0 mm.研究了不同高度下带小气泡的Janus颗粒撞击气泡的行为特征.结果表明:Janus颗粒不同润湿性表面撞击气泡时的行为特征存在明显差异,当超疏水侧接触气泡时,会沿着气泡表面无旋转地滑到气泡底部;当亲水侧接触气泡时,会先沿着气泡表面滑行一段距离,随后发生旋转,对气泡造成强烈扰动;而亲水-超疏水分界面接触气泡时,颗粒会在接触的瞬间开始旋转.当Janus颗粒具有一定的高度撞击气泡时,一般以亲水面首先与气泡接触,随高度的增加,Janus颗粒拉扯气泡变形的程度增加.基于受力分析发现:Janus颗粒发生旋转的主要原因是不同润湿性表面所受毛细力作用点和方向的不同,相应地产生旋转力矩.

In order to better apply amphiphilic Janus particles to phase change heat transfer,the hydrophilicsuperhydrophobic Janus particles are prepared with copper balls.The particle size is 1.0 mm and the bubble diameter is 3.0 mm.The behavior of Janus particle with small bubbles impinging on bubbles at different heights is studied.The falling heights are 0,10.0,20.0,30.0 and 40.0 mm.The results show that there are obvious differences in behavior characteristic among Janus particles with different wettability surfaces when they hit the bubble.When the superhydrophobic side contacts the bubble,it will slide to the bottom of the bubble without rotation along the bubble surface;when the hydrophilic side contacts the bubble,it will first slide along the bubble surface for a certain distance,and then rotate,resulting in strong disturbance to the bubble.When the interface between hydrophilic and superhydrophobic contacts the bubble,the particle will start to rotate at the moment of contact.When Janus particle impacts the bubble at a certain height,the hydrophilic surface generally contacts bubble first.With the increase of height,the degree of deformation of Janus particles pulling bubbles increases.The force analysis shows that the main reason for the rotation of Janus particles is that the action points and directions of capillary force acting on different wettable surfaces are different,resulting in corresponding rotation torque.