A Study of Drop-Microstructured Surface Interactions during Dropwise Condensation with Quartz Crystal Microbalance.

Junwei Su,Majid Charmchi,Hongwei Sun

doi:10.1038/srep35132

Abstract

Dropwise condensation (DWC) on hydrophobic surfaces is attracting attention for its great potential in many industrial applications, such as steam power plants, water desalination, and de-icing of aerodynamic surfaces, to list a few. The direct dynamic characterization of liquid/solid interaction can significantly accelerate the progress toward a full understanding of the thermal and mass transport mechanisms during DWC processes. This work reports a novel Quartz Crystal Microbalance (QCM) based method that can quantitatively analyze the interaction between water droplets and micropillar surfaces during different condensation states such as filmwise, Wenzel, and partial Cassie states. A combined nanoimprinting lithography and chemical surface treatment approach was utilized to fabricate the micropillar based superhydrophobic and superhydrophilic surfaces on the QCM substrates. The normalized frequency shift of the QCM device together with the microscopic observation of the corresponding drop motion revealed the droplets growth and their coalescence processes and clearly demonstrated the differences between the three aforementioned condensation states. In addition, the transition between Cassie and Wenzel states was successfully captured by this method. The newly developed QCM system provides a valuable tool for the dynamic characterization of different condensation processes.

Highlights

Dropwise condensation (DWC) on hydrophobic surfaces is attracting attention for its great potential in many industrial applications, such as steam power plants, water desalination, and de-icing of aerodynamic surfaces, to list a few
This paper presents a Quartz Crystal Microbalance (QCM) based technique to quantitatively measure the liquid/solid interface changes during dropwise condensation on flat and micro-structured surfaces
The micro-structured surfaces were fabricated on the bare QCM substrates by nanoimprinting lithography technique

Summary

Introduction

Dropwise condensation (DWC) on hydrophobic surfaces is attracting attention for its great potential in many industrial applications, such as steam power plants, water desalination, and de-icing of aerodynamic surfaces, to list a few. Several fabrication methods have been reported to produce biomimetic roughness-induced superhydrophobic surfaces, such as plasma-enhanced chemical vapor deposition[12], conventional photolithography and etching[13], self-assembled monolayers on nanostructures[14], template-based extrusion[15], electrospinning[16], and some other techniques such as a slippery liquid-infused porous surface[17], and layer-by-layer deposition[18]. Some of these surfaces have shown a great potential to further improve the efficiency of dropwise condensation[19].

Methods

Results

Conclusion