Optimum substrate stiffness in coalescence-induced droplet jumping

Area of Science:

• Soft matter physics
• Nanofluidics
• Surface science

Background:

• Droplet jumping on superhydrophobic surfaces is driven by surface energy conversion.
• Existing research primarily examines surface microstructure and droplet properties affecting jumping.
• The role of substrate properties in nanodroplet jumping remains less explored.

Purpose of the Study:

• To investigate coalescence-induced jumping of nanodroplets on soft substrates using molecular dynamics.
• To identify the optimal substrate stiffness for droplet jumping.
• To elucidate the underlying mechanisms governing droplet-substrate interactions during jumping.

Main Methods:

• Molecular dynamics simulations were employed to model nanodroplet coalescence and jumping.
• Analysis focused on the interactions between nanodroplets and soft substrates of varying stiffness.
• Droplet momentum was calculated by integrating substrate forces.

Main Results:

• An optimal substrate stiffness was identified for maximizing nanodroplet jumping velocity.
• The jumping dynamics are governed by a balance between impact and adhesion forces from the substrate.
• These forces are strongly dependent on the substrate's stiffness.

Conclusions:

• Substrate stiffness is a critical parameter controlling nanodroplet jumping on soft surfaces.
• Understanding these interactions can guide the design of novel microfluidic and self-cleaning applications.
• The findings provide fundamental insights into nanoscale droplet dynamics on compliant materials.