EMPLOYING SCANNING FORCE MICROSCOPY TO INVESTIGATE THE FREE SURFACE OF LIQUID MICROSTRUCTURES AND THEIR WETTING BEHAVIOR ON SMOOTH SURFACES: GATHERED EXPERIENCES

This article reports experiences gathered from systematic studies on the potential of scanning force microscopy to investigate the interface geometry and the wetting behavior of liquid microstructures placed on mica, glass, gold-coated, and uncoated silicon wafers. The liquids investigated are glycerin, polydimethylsiloxane (PDMS), squalane, pentadecane, hexadecane, heptadecane, 1,2-butanediol, 1,2-pentanediol, 1,2hexanediol, and 1,5-pentanediol. The experiments required fast and repetitive scanning of liquid structures. Different types of surface-modified cantilever/tip assemblies were employed, aiming at reducing the interfacial energy associated with uncoated silicon/silicon oxide cantilevers. Severe challenges concerning the stability and the reproducibility of such experiments are reported. Limitations of this method when applied to the free surface of liquid microstructures due to the small but ever-present interaction forces between the tip and the sample are also discussed.