Nano level study of superhydrophobic material with an acoustic multiresonance shear wave sensors
S.J. Kwoun, R.M. Lec, R.A. Cairncross, P. Shah and C.J. Brinker
Drexel University, US
superhydrophobic, acoustic, TSM,
Superhydrophobic (SH) materials have already enabled many novel applications in biotechnology and further progress in fabrication of SH materials depends on the availability of precise measurement tools capable of interrogating SH features at the nano-scale level where SH properties originate. The multiresonance Thickness-Shear Mode (TSM) technique, due to its nano-scale level interrogation mechanisms, is a candidate and provides the base for novel SH measurement tools. In this paper, the multiresonance TSM sensing technique was studied as a potential measurement tool for characterization of SH properties. Five samples of varying hydrophobicity were prepared by coating the sensors with SH films (TFPTMOS: trifluoropropyltrimethoxysilane) and subjecting the coating to various surface treatments, such as chemical surface treatment (by HMDS: hexamethyldisilizane) to increase the hydrophobicity, nano-scale geometrical treatment using silica nano particles, and UV lights surface treatment to decrease the hydrophobicity. After the samples were characterized with optical contact angle using sessile method and surface roughness by AFM, acoustic multi harmonic frequency responses of the samples were measured using TSM sensors. Although the macroscopic contact angles were similar (~ 150), the TSM responses varied in each sample and also showed different characteristics at each harmonics. Especially the SH sample with nano-particles and chemical HMDS treatments showed almost no frequency response when the sensor was subject to DI water. This shows that the sensor is capable of differentiating SH properties due to nano scale surface features.
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Nanotech 2006 Conference Program Abstract