Driven drops on heterogeneous substrates: onset of sliding motion

Area of Science:

• Physics
• Materials Science
• Surface Science

Background:

• Understanding fluid dynamics on heterogeneous surfaces is crucial for various applications.
• The behavior of drops is influenced by surface properties like hydrophobicity and hydrophilicity.
• Pinning and depinning phenomena dictate fluid motion on non-uniform substrates.

Purpose of the Study:

• To investigate the pinning and depinning dynamics of driven drops on heterogeneous substrates.
• To analyze the influence of driving force and heterogeneity amplitude on drop motion.
• To characterize different depinning mechanisms and the resulting stick-slip motion.

Main Methods:

• Numerical simulations were employed to model drop behavior.
• Two types of surface heterogeneity were considered: hydrophobic (pinning from front) and hydrophilic (pinning from back).
• The study systematically varied driving force and heterogeneity amplitude.

Main Results:

• Two distinct depinning mechanisms leading to sliding motion were identified.
• The amplitude of heterogeneity significantly impacts pinning and depinning thresholds.
• Complex stick-slip motion patterns were observed and characterized.

Conclusions:

• The study elucidates the fundamental mechanisms governing driven drop motion on heterogeneous surfaces.
• The findings provide insights into controlling fluid behavior in microfluidic devices and coatings.
• The identified depinning modes and stick-slip dynamics are critical for designing surfaces with tailored wetting properties.