Femtosecond Laser Processing Enabling Directional Propulsion of Leidenfrost Droplets on Various Material Substrates

Area of Science:

• Surface science and microfabrication
• Fluid dynamics at the microscale
• Materials science and engineering

Background:

• Controlling the motion of Leidenfrost droplets is crucial for various applications.
• Existing methods for droplet manipulation often lack versatility or require complex fabrication.
• The Leidenfrost effect, where a liquid vaporizes upon contact with a hot surface, creates a vapor layer that reduces friction.

Purpose of the Study:

• To develop a versatile and effective method for directional propulsion of Leidenfrost droplets.
• To demonstrate the applicability of the method across a wide range of materials.
• To explore potential applications leveraging controlled Leidenfrost droplet motion.

Main Methods:

• Fabrication of asymmetric microgroove arrays using one-step femtosecond laser direct writing.
• Precise control of laser scanning line spacing relative to microgroove width for directional propulsion.
• Experimental verification on various substrates including superhard alloys, semiconductors, and ceramics.

Main Results:

• Achieved effective directional propulsion of Leidenfrost droplets on asymmetric microgroove arrays.
• Demonstrated substrate-independent applicability across magnesium alloy, titanium alloy, silicon, silicon carbide, aluminum nitride, and sapphire.
• Successfully transported droplets on composite surfaces and propelled various volatile liquids.

Conclusions:

• Femtosecond laser direct writing provides a flexible and universal approach for fabricating microstructures to control Leidenfrost droplet motion.
• The developed method enables precise directional propulsion, trapping, targeted cooling, self-rotation, and electricity generation from Leidenfrost droplets.
• This technique opens new avenues for microfluidic applications in extreme high-temperature environments.