Directed Flow of Micromotors through Alignment Interactions with Micropatterned Ratchets

Area of Science:

• Active Matter Physics
• Soft Matter Science
• Microfluidics and Nanotechnology

Background:

• Controlling the motion of self-propelled particles (e.g., cells, synthetic micromotors) in out-of-equilibrium systems is a significant challenge.
• Random trajectories of active particles can be rectified by asymmetric cues, provided interactions exist between particles and cues.

Purpose of the Study:

• To demonstrate robust control over the spatiotemporal distribution of synthetic micromotors.
• To investigate the use of topographical features to direct particle flow and concentration.

Main Methods:

• Exploiting phoretic and hydrodynamic interactions between synthetic micromotors and local topographical features.
• Analyzing particle trajectories to observe the breaking of time-reversal symmetry.
• Developing a minimal theoretical model to identify key system parameters.

Main Results:

• Topographical features induce orientational alignment and geometrical asymmetry in micromotors, crucial for directional flow.
• Demonstrated the ability to concentrate micromotors in confined spaces.
• Identified specific interactions responsible for particle concentration effects.

Conclusions:

• The developed system offers robust control over the temporal and spatial distribution of synthetic micromotors.
• The interplay of topographical cues, particle properties, and interactions is key to rectifying active matter motion.
• This work provides a framework for designing active matter systems with predictable collective behavior.