选用典型模型大肠杆菌代表活性粒子,改变温度、悬浮液中菌数浓度、羧甲基纤维素钠(CMC)质量分数以及细菌活性(活菌和死菌),测量Rhodamine B在不同条件下剪切稀化流体基中的扩散系数。结果表明,大肠杆菌的加入可以有效强化Rhodamine B在剪切稀化流体基中的扩散;扩散系数与悬浮液温度和细菌菌数浓度呈正相关,而与CMC质量分数呈现出负相关;Rhodamine B的活性扩散系数与温度和菌数浓度呈正相关。均方位移随时间的变化图像表明,Rhodamine B在当前实验的时间段内表现为亚扩散行为,且随着扩散时间延长扩散指数变大。

Escherichia coli is a paradigmatic model system which is selected to represent the active particles.The diffusion coefficients of Rhodamine B in the shear thinning fluid based suspensions under different temperatures,different concentrations of bacteria in the suspensions,different mass fractions of sodium carboxymethyl cellulose (CMC) and different bacterial activities (live and dead) are measured.The experimental results show that the Escherichia coli can effectively enhance the diffusion of Rhodamine B in the shear thinning fluid based suspensions and the active particles can enhance the fluid mixing in the microfluidic device.The diffusion coefficient is positively correlated with suspension temperature and bacterial number concentration,but has negative correlation with CMC mass fraction.The self-propelling ability of bacteria is an important factor to improve the diffusion coefficient of Rhodamine B.The active diffusion coefficient of Rhodamine B was positively correlated with temperature and bacterial number concentration.Within the time of current experiments,the images of translational mean-squared displacements with time show that the diffusion mode of Rhodamine B is sub diffusive,and the sub diffusion exponent α increases with the increasing diffusion time.Due to self-propelling behavior,active particles can generate micro convection and micro disturbance which can weaken the "cage effect" of polymer molecular chains and promote the diffusion mode from sub diffusion to normal diffusion.

张泽(1999-),男,硕士生,研究方向为扩散传质,ze1803576287@163.com;许晓飞(1981-),男,博士,副教授,研究方向为微尺度多相流传热传质与废水处理,通讯联系人,xiaofei.xu@dlut.edu.cn。