Experiment And Numerical Study For The Motion Of Self-propelled Janus Particles

Self-propellant Janus particles are special types of active particles whose surfaces have two distinct physical or chemical properties. Under the different external conditions, concentration, temperature, light intensity, or other physical field gradients may be formed at both sides of Janus particles for their asymmetric distribution. In the micrometer scale, after the mixing of Janus particles which consist of the catalytic/non-catalytic surfaces and the solution, a gradient of molecules number will form between reaction-side/unreaction-side. The self-propelled motion will be generated by diffusion force which converse chemical energy into mechanical movement. This phenomenon has a great value on important applications such as in micro-electro- mechanical system,fluid mechanics and other areas;The research of self-propelled Janus particles also has important theoretical value such as condensed matter physics, materials anomalous diffusion, fractional Brownian motion and tropisms of single-celled organisms.This article first introduced the related background topic of the Janus particles, and summarizes the basic physical dynamics of the self-propelled motion of Janus particles and the law of motion starting from the previous experiment’s research. Analyzing the movement of Janus particles microspheres by PIV experiment records, getting the deflective elevation of Janus microsphere in motion by means of specialized image processing method and builting a numerical model of self-propelled Janus microsphere on the basis of Comsol Multiphysics coupling software. Next, we obtained the migration rate matching constant σ in numerical model on the basis of the self-propelled velocity VJanus by the experiment, and determining the angle φ and the separationdistance δ of microsphere from the substrate under the different conditions, discussing by the near wall’s impact to the typical macro statistical parameters(such as Deff, τR, etc.)by the angle φ and the separation distance.In addition, we obtained migration rate matching constant σ from the experimental data of Pt-Si O2 type Janus microspheres without considering the wall’s effect. And we studied three different shapes of self-propelled Janus particles and the results showed that cylindrical and ellipsoidal Janus particles have the faster self-propelled velocities and consumpted more fuel than that of spherical particles. For cylindrical particles, we studied the effect of different aspect ratios on the self-propulsion. The results showed that there is the optimal condition(the ratio of the diameter over length D/L is about0.28), at which both self-propelled velocity and fuel consumption are maximum. This study may provide a theoretical basis for the shape effect’s application of Janus particles.In a word, we obtained the the wall’s effect and shape’s effect of Janus particles.The results will be beneficial to understanding the mechanism of self-propulsion and designing micro-nano devices based on diffusiophoretic force. At the same time, the research method of combining experimental study and numerical simulation in this article will not only help to obtain the self-propelled Janus particle dynamics information, and explain its related laws. It has laid a certain foundation for later research progress of the project group.