自驱动Janus微球的分数Brownian运动研究

Study on Fractional Brownian Motion of Self-Propelled Janus Microspheres

Janus微球是形状规则但表面构成不同的特殊颗粒.在PIV实验平台上,以Pt-SiO2型Janus颗粒(Φ=1μm,Φ=2μm)为研究对象,获取了通过非对称催化分解H2O2产生自驱动情况下颗粒的不规则运动轨迹,通过统计得出不同观测时间下Janus颗粒在不同浓度H2O2溶液(0%,2.5%,5%,10%和15%)中的Hurst指数,实验清晰地表明了颗粒轨迹所具有的无规则运动与定向运动的叠加以及反常扩散特征.随后将这一复杂运动分解为随机的Brownian(布朗)运动、自驱动及随机转动的共同作用,并得出了不同因素所主导的特征时间尺度,合理地解释了所观察到的现象.

Janus microspheres are a special class of particles with regular shape but irregular surface composition. On the PIV experimental platform, a serf-propulsion experiment about Pt- SiO2 Janus microspheres with 1 μm and 2 μm diameters was carried out. The stochastic trajec- tories of the particles self-propelled by the asymmetrical catalytic decomposition of H2O2 were obtained. The Hurst indexes related to different observation time intervals were calculated through statistic analysis of the particles suspended in different-concentration （0%, 2.5%, 5%, 10% and 15% ） solutions. From the experimental data, it is clear that the stochastic trajectory of a Janus microsphere is the superposition of a random motion and a directional motion, and the particle undergoes abnormal diffusion. Then, the current complex motion is deemed as the combined action of Brownian motion, serf-propulsion and random rotation. The characteristic time scales, within which different dynamic factors are dominating, are obtained, and the mod- el presents a reasonable explanation about the observed phenomena.