Surface Nanostructures Promote Droplet Splash on Hot Substrates

Area of Science:

• Fluid dynamics
• Surface science
• Nanotechnology

Background:

• Droplet splash is a common phenomenon observed during liquid impacts on surfaces.
• Elevating substrate temperature typically suppresses droplet splash, which can be detrimental in applications like spray cooling and combustion.
• The influence of surface wettability on droplet splash dynamics is well-documented.

Purpose of the Study:

• To investigate the effect of nanostructured surfaces on droplet splash dynamics, specifically in relation to substrate temperature.
• To explore the potential of nanostructures to overcome the temperature-dependent suppression of droplet splash.
• To develop a theoretical framework for understanding splash regimes based on air evacuation and flow instabilities.

Main Methods:

• Experimental investigation of droplet impact on nanostructured surfaces at varying substrate temperatures.
• Manipulation of air evacuation time using surface nanostructures.
• Development of a theoretical criterion to distinguish between different splash regimes.

Main Results:

• Nanostructured surfaces nullify the splash suppression effect of substrate temperature.
• Precise control over the splash threshold and its temperature dependence is achieved by manipulating air evacuation time via nanostructures.
• A theoretical criterion is proposed, correlating splash regimes with the competition between air evacuation and flow instabilities.

Conclusions:

• Surface nanostructures play a critical role in controlling droplet splash dynamics, independent of substrate temperature effects.
• The findings provide a novel pathway for tailoring splash behavior in various industrial scenarios, such as spray cooling and combustion.
• Understanding the interplay between air evacuation and flow instabilities is key to predicting and controlling droplet splash regimes.