Experimental Study and Analysis of Dropwise Condensation Using Quartz Crystal Microbalance

This work reports a novel Quartz Crystal Microbalance (QCM) based method to analyze the droplet-micropillar surface interaction quantitatively during dropwise condensation. A combined nanoimprinting lithography and chemical surface treatment approach was utilized to directly fabricate the micropillar based superhydrophobic surface on the QCM substrate. The normalized frequency shift of the QCM device and the microscopic observation of the corresponding nucleation, drop growth, and drop coalescence processes clearly demonstrate the different characteristics of these condensation states. In addition, a synchrosqueezed wavelet spectrum based multi-resolution technique was utilized to analyze the resonant signal from the QCM sensor in both time and frequency domains simultaneously. An integrated discrete system modeling along with a hybrid signal and image processing approach was adopted to identify the response of the micropillars under different stages of dropwise condensation (DWC). The outcome of this signal processing research leads to a fundamental understanding of DWC spanning multiple time and length scales. The proposed study will also contribute to an in-depth understanding of different hydrophobic surfaces and DWC through this advanced signal processing and surface treatment. The developed QCM system provides a valuable tool for the dynamic characterization of different condensation processes.