Study Of The Diffusiophoresis Force And Motion Characteristics Of Janus Particle Based On Multi-component Lattice Boltzmann Method

Janus particles are artificially synthesized active micro-nanoparticles with potential applications in the field of micro-object.Janus particles are anisotropic,including anisotropic shape and chemical surface.The Janus particles studied in this paper include the above two cases,which are spherical micro-scale particles coated with Pt on one side and cylindrical micro-scale particles coated with Pt and Au on both sides.Based on the lattice Boltzmann method(LBM)simulating,the propelled forces of spherical and cylindrical particles are studied—diffusion force and motion characteristics.The self-propelled motion of Janus particles at the micro-scale is a complex multi-field coupling and multi-time scale motion.And motion of the Janus particle exhibits different motion characteristics at different time scales.In the experiment,it is observed that the motion of particles at micro-scale is complex and diverse,and its mechanism is hard to explain.Therefore,it is necessary to explore the motion mechanism of micro-scale particles in a direct numerical simulation method,and establish a simulated platform to lay a foundation for its application prospects.Firstly,the flow field and the concentration field are calculated by the double distribution function lattice Boltzmann model.The DDF-LBM is a simple numerical method for simulating multi-component fluids.The flow field described by velocity distribution function is used to calculate the Brownian force and Stokes resistance of Janus particle.The concentration field described by concentration distribution function combine osmotic pressure model to calculate the diffusion force,which is compared with the experimentally fitted diffusion force.The error is within 5%,which verifies the correctness of the model.Secondly,all the calculated forces of the particles are applied to the spherical Janus particles to simulate their motion characteristics,which combines the FLB?moving boundary and grid-refined technology.The motion parameters include the mean square displacement and the translational diffusion coefficient obtained in the experiment.The simulation results show that the spherical Janus particles have different motion characteristics at different time scales: Brownian motion at small time scale and directional motion at large time scale.The simulation results are compared with experimental and theoretical analysis to verify its correctness,so as to establish a complete numerical simulation method to describe the motion characteristics of micron-sized particles across time scales.Finally,the same method is utilized to simulate the motion characteristics of cylindrical Janus particles,including translational diffusion coefficient,rotational diffusion coefficient and orientation,etc.The different motion characteristics of cylindrical Janus particles at different time scales are obtained.Motion characteristics of cylindrical Janus particles with different aspect ratios are compared to provide guidance for the study of more complex particle motion characteristics.