Electric field makes Leidenfrost droplets take a leap

Area of Science:

• Fluid dynamics
• Electromagnetism
• Surface science

Background:

• Leidenfrost droplets levitate on a vapor layer above a hot surface.
• Their motion is typically governed by surface tension and buoyancy forces.
• External fields can significantly alter droplet behavior.

Purpose of the Study:

• To investigate the effect of external electric fields on Leidenfrost droplets.
• To understand the charge dynamics and energy transfer mechanisms.
• To model the droplet's bouncing behavior and escape from the hot surface.

Main Methods:

• Subjecting Leidenfrost droplets to a strong vertical electric field.
• Analyzing droplet trajectories to infer charge evolution.
• Developing a model based on a conducting sphere with intermittent electrical contact.
• Examining kinetic and potential energies during bouncing.

Main Results:

• Droplets exhibit progressively higher bounces, defying gravity in strong electric fields.
• Droplet charge decreases in steps during evaporation, proportional to surface area.
• An electro-capillary instability dictates discharge intervals.
• Droplets experience energy boosts, synchronizing free fall and oscillation.

Conclusions:

• The electric field induces a novel bouncing and charge shedding behavior in Leidenfrost droplets.
• Electrical contact with the hot plate, governed by electro-capillary instability, is key to charge dynamics.
• Energy boosts help droplets escape the hot surface by overcoming damping and synchronizing motion.