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微纳马达的研究是一个多学科交叉的新兴领域.其中,Janus微马达利用自身两面异性导致的局部梯度场而产生自驱动现象,引起了学界的普遍关注.本文主要基于目前已开展的工作并借鉴国内外的一些最新成果,以期对Janus球形微马达的物理特征给出全面的描述.针对铂-二氧化硅(Pt-SiO_2)型Janus微球在过氧化氢溶液中发生的自驱动,通过实验和数值模拟分析了其两种自驱动形式(自扩散泳动和微气泡推进)的物理机制和运动特征.直径小于5mm的Janus微球发生自扩散泳动,通过无量纲均方位移随时间的变化揭示了微球平动经历由纯布朗运动、扩散泳动到类布朗运动的过程,给出了特征时间及不同阶段的主导物理因素.位移概率分布可以表征非高斯性,并分析布朗力矩主导的旋转特性并讨论壁面限制及剪切流的影响.直径20~50mm微球可观测到微气泡推进,微球位移揭示了随气泡尺寸增长,微球经过自扩散泳、气泡生长和气泡溃灭推进3个阶段组成的周期运动.Rayleigh-Plesset(R-P)方程则揭示了依次由黏性力、表面张力及气泡周围流体压力控制下的气泡生长标度率.本文还从应用角度介绍了交变电场下,利用介电泳操控Janus微球的微穿梭输运(microshuttle)技术,并讨论了自扩散泳与自电泳差别及微气泡推进型微马达效率提高等问题.
The research of micro-nano motor is a new field of multi-disciplinary crossover, in which the Janus micro-motor generates self-driven phenomenon by using the local gradient field caused by the two-sided heterosexuality and has aroused widespread concern in the academic field.This paper is based on the work done so far Drawing on the latest achievements at home and abroad, this paper gives a general description of the physical characteristics of the Janus micro-motor.For the self-driving of the Pt-SiO_2-type Janus microspheres in hydrogen peroxide solution, The physical and kinetic characteristics of two self-driven forms (self-diffusion motions and microbubble projectiles) were analyzed experimentally and numerically.The Janus microspheres with diameter less than 5 mm appeared self-diffusion motions by dimensionless mean square displacement with time Reveals the process of microstrip translational motion from pure Brownian motion to diffusion-like Brownian motion, and gives the dominant physical factors of characteristic time and different phases.The displacement probability distribution can characterize the non-Gaussianity and analyze the Brownian moment Leading rotational properties and discussing the effects of wall confinement and shear flow.Micro-bubbles were observed for microspheres with a diameter of 20-50 mm and the microsphere displacements were revealed with the bubble ruler Growth, and the microspheres advance cyclically through three stages of self-diffusion, bubble growth and bubble collapse. The Rayleigh-Plesset (RP) equation reveals that in turn the viscous force, the surface tension and the fluid pressure around the bubble Bubble growth and scaling rate.The microshuttle technology of Janus microspheres by dielectrophoresis under alternating electric field was also introduced in this paper.The difference between self-diffusion and self-electrophoresis and microbubble propellant Micro-motor efficiency and other issues.