Xie Chenliang, Liu Yanan, Luo Hao, Jing Guangyin
School of Physics, Northwest University, Xi'an 710127, China.
Micromachines (Basel). 2022 May 8;13(5):746. doi: 10.3390/mi13050746.
Superdiffusion processes significantly promote the transport of tiny passive particles within biological fluids. Activity, one of the essential measures for living matter, however, is less examined in terms of how and to what extent it can improve the diffusivity of the moving particles. Here, bacterial suspensions are confined within the microfluidic channel at the state of bacterial turbulence, and are tuned to different activity levels by oxygen consumption in control. Systematic measurements are conducted to determine the superdiffusion exponent, which characterizes the diffusivity strength of tracer particles, depending on the continuously injecting energy converted to motile activity from swimming individuals. Higher activity is quantified to drastically enhance the superdiffusion process of passive tracers in the short-time regime. Moreover, the number density of the swimming bacteria is controlled to contribute to the activity, and then to strengthen the super-diffusivity of tracers, distinguished by regimes with and without collective motion of interacting bacteria. Finally, the non-slip surfaces of the microfluidic channel lower the superdiffusion of immersed tracers due to the resistance, with the small diffusivity differing from the counterpart in the bulk. The findings here suggest ways of controlled diffusion and transport of substances within the living system with different levels of nutrition and resources and boundary walls, leading to efficient mixing, drug delivery and intracellular communications.
超扩散过程显著促进了生物流体中微小被动粒子的传输。然而，活性作为生命物质的基本衡量指标之一，在其如何以及在多大程度上能够提高运动粒子的扩散率方面却较少受到研究。在此，细菌悬浮液在细菌湍流状态下被限制在微流控通道内，并通过控制耗氧量调节到不同的活性水平。进行了系统测量以确定超扩散指数，该指数表征示踪粒子的扩散强度，它取决于从游动个体连续注入转化为运动活性的能量。较高的活性被量化为在短时间内显著增强被动示踪剂的超扩散过程。此外，控制游动细菌的数量密度以促进活性，进而增强示踪剂的超扩散性，这通过有或没有相互作用细菌集体运动的状态来区分。最后，微流控通道的非滑动表面由于阻力降低了浸入示踪剂的超扩散，其小扩散率与主体中的对应物不同。此处的研究结果表明了在具有不同营养和资源水平以及边界壁的生命系统内控制物质扩散和传输的方法，从而实现高效混合、药物递送和细胞内通讯。
