Self-Propulsion and Shear Flow Align Active Particles in Nozzles and Channels

Active particles consume energy stored in the environment and convert it into mechanical motion. Many potential applications of these systems involve their flowing, extrusion, and deposition through channels and nozzles, such as targeted drug delivery and out-of-equilibrium self-assembly. However, understanding their fundamental interactions with flow and boundaries remain incomplete. Herein, experimental and theoretical studies of hydrogen peroxide (H2O2) powered self-propelled gold-platinum nanorods in parallel channels and nozzles are conducted. The behaviors of active (self-propelled) and passive rods are systematically compared. It is found that most active rods self-align with the flow streamlines in areas with high shear and exhibit rheotaxis (swimming against the flow). In contrast, passive rods continue moving unaffected until the flow rate is very high, at which point they also start showing some alignment. The experimental results are rationalized by computational modeling delineating activity and rod-flow interactions. The obtained results provide insight into the manipulation and control of active particle flow and extrusion in complex geometries.

Automated summary

Experimental and theoretical studies were conducted on self-propelled gold-platinum nanorods powered by H2O2 in parallel channels and nozzles, revealing that active rods self-align with flow streamlines and exhibit rheotaxis, while passive rods require high flow rates to start aligning. Computational modeling helps rationalize activity and rod-flow interactions in complex geometries.