Hydrophobicity of Electrospun Nanofibers Films Characterized by a Quartz Crystal Microbalance

The quartz crystal microbalance (QCM) sensor is used to study the dynamic characteristic of hydrophobic nanofiberous surfaces. The nanofibrous films of polymethyl methacrylate (PMMA), PMMA/ Polydimethylsiloxane (PDMS) and Polyacrylonitrile (PAN) were prepared with an electrospinning process for different hydrophobicity (wettability). The mechanical impedance analysis of DI water on a fibrous coated QCM surface is able to quantitatively characterize the hydrophobicity of these nanofibers surfaces. The two layers including a viscoelastic nanofiber film and a liquid layer result in a nonlinear combination of mechanical impedances. To simplify the analysis, an apparent viscosity was introduced in the analysis to account for the surfacial slip effect. The experimental results showed that the hydrophobic surface resulted in small mechanical impedance loading and low value of apparent viscosity, while the hydrophilic surface generated large mechanical impedance and gave high value of apparent viscosity.