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Dielectrowetting Control of Capillary Force (Cheerios Effect) between Floating Objects and Wall for Dielectric Fluid
Junqi Yuan1, Jian Feng1, Sung Kwon Cho1
1Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA 15237, USA.
Micromachines
|April 3, 2021
Summary
This study demonstrates active control over the "Cheerios effect" by manipulating sidewall wettability using dielectrowetting. This allows for reversible capillary forces, enabling controlled movement of floating objects.
Area of Science:
- Fluid dynamics
- Surface science
- Microfluidics
Background:
- The
- Cheerios effect
- describes capillary interactions between floating objects and adjacent surfaces, influencing their attraction or repulsion based on physical properties.
- Controlling these capillary forces is crucial for manipulating small floating objects.
Purpose of the Study:
- To investigate the active control of capillary forces on floating objects in a dielectric fluid.
- To demonstrate the reversal of capillary forces (attraction/repulsion) by altering sidewall wettability.
Main Methods:
- Introduction of dielectrowetting to the sidewall to actively control the contact angle.
- Experimental analysis of floating object trajectories under varying sidewall conditions and tilting angles.
- Comparison of theoretical models with experimental data.
Main Results:
- Successful active control and reversal of capillary forces (attraction to repulsion) by adjusting sidewall wettability via dielectrowetting.
- Demonstration of a theoretical relationship between sidewall tilting angle and capillary force, validated by experimental results.
- Observation of continuous motion of a floating object driven by sequentially activated dielectrowetting electrode pads.
Conclusions:
- Dielectrowetting provides an effective method for actively controlling and reversing capillary forces, offering precise manipulation of floating objects.
- The study validates the importance of sidewall wettability and tilting angle in governing capillary interactions.
- This technique enables controlled movement and positioning of micro-objects in fluidic environments.
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