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Low Reynolds number flows and Microswimming

The hydrodynamic interaction of micro particles or microorganisms with their environment plays a key role in a number of applications in biomechanics, biomaterials production, and microdevices. The slippage characteristics of homogeneous or geometrically patterned surfaces influence the particle motion in low Reynolds number flow. Recent work demonstrated the ability of microswimmers to move along a circular path near a rigid wall and the possibility of reversing direction of rotation near a liquid-air interface.
A fundamental understanding of these interactions is useful in the design of functionalized surfaces and the selection of particles or microorganisms based on their geometrical or mobility characteristics, taking advantage of their particular hydrodynamic behaviour in a wide range of applications, including mixing or energy production.

In order to understand the fluid dynamic interactions between passive or self propelled bodies and surfaces with different characteristics (thus different kinds of boundary conditions), the low Reynolds equations are numerically solved by exploiting the Boundary Element Method. This allows to handle complex geometries (actual bacteria and patterned walls) and different boundary conditions, such as no-slip, perfect-slip or partial slip.  


Our work focuses on the interactions between microswimmers and different kind of surfaces (adherent walls, liquid-air interfaces, superhydrophobic surfaces), in order to describe how different confinements can affect the fluid dynamic behaviour of microswimmers.    

A deeper comprehension of these interactions can lead to the design of surfaces or environments specifically studied to passively "guide" the microswimmers' motion. 

Passive bodies on SH surfaces

We study the motion of passive bodies (such as microparticles) in presence of complex surfaces, where different boundary conditions apply, such as superhydrophobic walls in Cassie state. 

Results show unexpected and non trivial behaviours of particles trajectories, when moving near SH surfaces.