Coplanar Electrowetting-Induced Droplet Detachment from Radially Symmetric Electrodes

Area of Science:

• Physics
• Engineering
• Materials Science

Background:

• Electrowetting is a technique used to manipulate droplets on surfaces.
• Previous models for droplet detachment in air using electrowetting did not account for gravitational effects.
• Accurate prediction of droplet detachment is crucial for microfluidic applications.

Purpose of the Study:

• To demonstrate electrowetting-induced droplet detachment in air using a single voltage pulse.
• To develop and validate models for predicting droplet detachment thresholds.
• To incorporate gravitational potential energy changes into detachment models.

Main Methods:

• Experiments were conducted using electrowetting devices with coplanar electrodes.
• Droplets of varying volumes were detached using single voltage pulses in air.
• Two models were developed, one including gravitational potential energy, and compared to experimental data.

Main Results:

• The incorporation of gravitational potential energy significantly improved the accuracy of detachment predictions.
• The updated models successfully predicted the critical electrowetting number for droplet detachment.
• The models captured the experimentally observed increase in required voltage with increasing droplet volume.

Conclusions:

• New models accurately predict electrowetting-induced droplet detachment in air by including gravitational effects.
• These models enhance the understanding and control of droplet manipulation in microfluidic systems.
• The findings are particularly relevant for 3D digital microfluidics applications involving droplet ejection in air.