Spontaneous helical flows in active nematics lying on a cylindrical surface

Area of Science:

• Soft Matter Physics
• Fluid Dynamics
• Materials Science

Background:

• Active nematic gels exhibit spontaneous flows driven by self-propelled particles.
• Geometric confinement can significantly alter the behavior of active materials.
• Understanding these effects is crucial for designing microfluidic devices.

Purpose of the Study:

• To investigate the impact of geometric confinement on the spontaneous flow of active nematic gels.
• To analyze the interplay between curvature, flow, director alignment, and activity.
• To identify key parameters influencing flow patterns in confined active nematics.

Main Methods:

• Utilized the two-dimensional Ericksen-Leslie model for active nematic gels.
• Assumed flow on a cylindrical surface with degenerate tangential anchoring.
• Employed linear approximation of motion equations for analysis.

Main Results:

• Extrinsic curvature promotes director alignment parallel to the cylinder axis.
• Curvature increases the critical threshold for spontaneous flow compared to flat surfaces.
• Observed helical flow patterns and double periodicity in azimuthal and axial variables.
• Key parameters include activity coefficient, tumbling parameter, and viscosity ratio.

Conclusions:

• Geometric confinement plays a critical role in directing the spontaneous flow of active nematic gels.
• The helical flow patterns and director oscillations offer insights for microfluidic applications.
• Results provide guidance for designing active microfluidic devices with specific material properties.