Behavior characteristics of Janus particles impacting bubbles

Abstract

In order to better apply amphiphilic Janus particles to phase change heat transfer, the hydrophilic-superhydrophobic 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.