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Optimal Control of Droplets on a Solid Surface Using Distributed Contact Angles.
Henning Bonart1, Christian Kahle2, Jens-Uwe Repke1
1Technische Universität Berlin, Process Dynamics and Operations Group, Straße des 17. Juni 135, 10623 Berlin, Germany.
Langmuir : the ACS Journal of Surfaces and Colloids
|July 7, 2020
Summary
This study demonstrates optimal control for droplet shape and position in microfluidics using variable contact angles. This approach automates droplet manipulation for high-throughput applications.
Area of Science:
- Fluid dynamics
- Microfluidics
- Control theory
Background:
- Droplet manipulation is crucial for microfluidic applications.
- Automating droplet control for high-throughput screening is challenging.
- Model-based optimal control strategies are rarely employed for droplet automation.
Purpose of the Study:
- To demonstrate optimal control of droplet shape and position on an inclined surface.
- To explore the use of spatially and temporally varying contact angles as a control variable.
- To provide a foundational method for advanced microfluidic control systems.
Main Methods:
- Utilizing control patches, similar to electrowetting, to modulate static contact angles.
- Employing gradient-based optimization to compute mathematically optimal contact angle distributions.
- Simulating droplet dynamics using the Cahn-Hilliard-Navier-Stokes equations.
Main Results:
- Successfully demonstrated optimal control over droplet shape and position.
- Calculated optimal contact angle distributions for precise droplet manipulation.
- Validated the Cahn-Hilliard-Navier-Stokes model for droplet dynamics.
Conclusions:
- The presented method offers a pathway for automated, model-based control of microfluidic droplets.
- This work serves as a fundamental step towards more complex optimal design and control in microfluidics.
- Spatially and temporally controlled contact angles are effective for precise droplet manipulation.
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