Experimental investigation of clustering behavior of active particle suspension under quasi-1D spatial confinement

Chong-Wai Io^1*, Yu-Yao Lee¹

¹Department of physics, National Chung-Cheng University, Chia-Yi, Taiwan

* Presenter:Chong-Wai Io, email:phycwio@ccu.edu.tw

The suspension of active particle with tunable self-propulsion strength could be one of the simplest non-equilibrium systems. With increasing the self-propulsion strength, such a system can bridge the equilibrium state with Brownian motion to far from equilibrium state with heterogeneous motion, even which is kept in homogeneous background (without any consideration of boundary effect). The spatial confinement is an additional factor to introduce boundary effect to induce spatial heterogeneity. In this work, by using the laser-activated thermophoretic type active particle suspension confined in high aspect ratio micro-channel, in which the spatial confinement can be considered as quasi-1D spatial confinement, we found that under the cooperation of inter-particle interaction, particle self-propulsion strength, and spatial confinement, such system can exhibit some special mesoscopic structures, such as sausage-like bundle at the channel center, quasi-periodic separated clusters located at channel center, aperiodic cluster near to the boundary, and propulsion induced boundary accumulation at the channel wall. Those findings are helpful for micro-particle manipulation at mesoscopic scale. The underlying formation mechanism of those structures will be discussed and reported.

Keywords: Active particle suspension, Heterogeneous dynamics, Micro-channel