Near Axisymmetric Partial Wetting Using Interface-Localized Liquid Dielectrophoresis

Area of Science:

• Physics
• Materials Science
• Surface Science

Background:

• Surface wetting is governed by surface free energy, influencing interactions between solid, liquid, and vapor phases.
• Liquid dielectrophoresis (L-DEP) is a bulk force typically acting on dielectric liquid dipoles, not usually considered a localized interfacial effect.
• Previous research showed L-DEP could induce oil droplet spreading along parallel electrodes, forming liquid stripes.

Purpose of the Study:

• To investigate the use of spiral electrodes and phase-shifted signals to achieve axisymmetric droplet spreading via L-DEP.
• To explore the potential of L-DEP for enhanced wetting control and film formation.
• To analyze the voltage dependence of contact angle and derive a scaling law for L-DEP effects.

Main Methods:

• Utilizing spiral-shaped electrodes actuated by four 90° successive phase-shifted electrical signals.
• Inducing L-DEP at a solid-liquid interface using a non-uniform electric field.
• Conducting experimental observations of droplet behavior and contact angle measurements.
• Analyzing the relationship between applied voltage, electrode size, and wetting phenomena.

Main Results:

• Achieved near axisymmetric spreading of dielectric liquid droplets using spiral electrodes.
• Demonstrated L-DEP induced wetting capable of forming liquid films, an effect not achievable with standard electrowetting.
• Confirmed the reversibility of the spreading process, allowing controllable manipulation of partial wetting states.
• Observed a quadratic dependence of the cosine of the contact angle on the applied voltage.
• Deduced a scaling law relating the L-DEP effect strength to electrode dimensions.

Conclusions:

• Spiral electrode configurations actuated by phase-shifted signals enable precise control over L-DEP induced wetting.
• L-DEP offers unique capabilities for achieving film formation and dynamic wetting control beyond conventional electrowetting.
• The established voltage and electrode size dependencies provide a framework for optimizing L-DEP applications in microfluidics and surface engineering.