Active fluid encapsulated in a water-in-oil droplet was reported to develop a spontaneous circulation whose onset depended on droplet geometry. However, how the dynamics surrounding the droplet influence the active fluid circulation remains poorly understood. Here, we used a combined experimental and modeling approach to demonstrate that the intradroplet circulation can be controlled through the flow coupling across the water–oil interface between active fluid and oil. We immersed the kinesin-driven, microtubule-based active fluid in a water-in-oil droplet that was compressed to a cylinder-like geometry. The droplet geometry supported the formation of intradroplet circulatory flows, but the circulation was suppressed when the thickness of the oil layer surrounding the droplet decreased. A combination of experiments and models demonstrated that the flow transition was due to active fluid–oil flow coupling across the interface, with a millimeter–scale coupling length. In addition, two millifluidic devices were developed that could trigger or suppress intradroplet circulatory flows in real time: One device achieved this goal by locally deforming the droplet and the other by tuning the thickness of the surrounding oil layer without contacting the droplet. Our work highlights the role of interfacial dynamics in self-organization of active fluid within a droplet.

• This report represents the work of one or more WPI undergraduate students submitted to the faculty as evidence of completion of a degree requirement. WPI routinely publishes these reports on its website without editorial or peer review.

Creator

• Chen, Yen-Chen

Publisher

• Worcester Polytechnic Institute

Identifier

• E-project-051621-204949
• 24706

Keyword

• Millifluidic Device
• Interfacial Coupling
• Active Fluid

Advisor

• Wu, Kun-Ta

Year

• 2021

Date created

• 2021-05-16

Resource type

• Major Qualifying Project

Major

• Mechanical Engineering

Rights statement

• In Copyright