Characteristic spatial scale of vesicle pair interactions in a plane linear flow

Area of Science:

• Fluid dynamics
• Biophysics
• Microfluidics

Background:

• Vesicles are fundamental units in biological systems and synthetic materials.
• Understanding vesicle interactions in flow is key to predicting suspension behavior.
• Microfluidic devices offer precise control for studying such interactions.

Purpose of the Study:

• To experimentally investigate the interaction dynamics of two vesicles in a controlled microfluidic flow.
• To quantify the influence of vesicle proximity on individual vesicle motion.
• To determine the maximum volume fraction for non-interacting vesicle suspensions.

Main Methods:

• Utilizing a microfluidic four-roll mill to generate a plane linear flow.
• Trapping and observing the motion of two interacting vesicles.
• Measuring the back-reaction of a single vesicle on the surrounding velocity field.

Main Results:

• Vesicle dynamics, specifically tank-treading motion, are significantly affected by nearby vesicles.
• This interaction effect is observed at separation distances up to 3.2-3.7 times the vesicle's effective radius.
• Experimental data supports an upper bound for non-interacting vesicle suspensions between φ = 0.08-0.13.

Conclusions:

• Vesicle-vesicle interactions extend beyond immediate contact, influencing dynamics at larger separations.
• The findings provide critical parameters for modeling concentrated vesicle suspensions.
• This research advances the understanding of fluid-structure interactions in microscale systems.