Maximizing propulsive thrust of a driven filament at low Reynolds number via variable flexibility

Area of Science:

• Fluid dynamics
• Biophysics
• Robotics

Background:

• Locomotion at low Reynolds numbers is challenging due to inertia absence.
• Purcell's scallop theorem states rigid bodies cannot generate propulsion.
• Uniform filaments have optimal stiffness for propulsion, but improvements are possible.

Purpose of the Study:

• To investigate how spatially varying flexibility impacts propulsive performance.
• To demonstrate enhanced propulsion through optimized flexibility distributions.
• To reveal design principles for micro-swimmer propulsion.

Main Methods:

• Analyzing propulsive thrust of a periodically driven filament.
• Comparing rigid, uniform, and spatially varying flexibility cases.
• Investigating configuration-dependent optimal flexibility.

Main Results:

• Rigid filaments generate zero propulsion.
• Uniform filaments achieve maximal force at a specific stiffness.
• Spatially varying flexibility significantly enhances propulsion.
• Optimal flexibility depends on filament attachment (clamped vs. hinged).

Conclusions:

• Spatially varying flexibility offers a powerful strategy to enhance micro-swimmer propulsion.
• Design principles for optimizing flexibility are configuration-dependent.
• Findings can guide the development of efficient synthetic micro-swimmers for biomedical applications.