Control of Wettability of Molecularly Thin Liquid Films by Nanostructures

Abstract

The patterning of liquid thin films on solid surfaces is very important in various fields of science and engineering related to surfaces and interfaces. A method of nanometer-scale patterning of a molecularly thin liquid film on a silicon substrate using the lyophobicity of the oxide nanostructures has recently been reported (Fukuzawa, K.; Deguchi, T.; Kawamura, J.; Mitsuya, Y.; Muramatsu, T.; Zhang, H. Appl. Phys. Lett. 2005, 87, 203108). However, the origin of the lyophobicity of the nanostructure with a height of around 1 nm, which was fabricated by probe oxidation, has not yet been clarified. In the present study, the change in thickness of the liquid film on mesa-shaped nanostructures and the wettability for the various combinations of the thickness of the liquid films and the height of ridge-shaped nanostructures were investigated. These revealed that lyophobicity is caused by a lowering of the intermolecular interaction between the liquid and silicon surfaces by the nanostructure and enables the patterning of a liquid film along it. The tendency of the wettability for a given liquid film and nanostructure size can be predicted by estimating the contributions of the intermolecular interaction and capillary pressure. In this method, the height of the nanostructure can control the wettability. These results can provide a novel method of nanoscale patterning of liquid thin films, which will be very useful in creating new functional surfaces.

Polymer spreading on substrates with nanoscale grooves using molecular dynamics

“…Comparing published works that study liquid spreading on substrates with unidirectional nanoscale grooves, we find that similar observations are documented for different substrates, groove shapes, and liquids, using both simulations and experiments. However, some researchers explain that liquid spreading is accelerated along a groove [10,12], whereas others describe an energy barrier that seemingly confines spreading perpendicular to the groove direction [11,13,16].…”

Polymer Spreading on Unidirectionally Nanotextured Substrates Using Molecular Dynamics

“…The ability to create anisotropic spreading in particular, which enables liquid spreading to occur in a user-specified direction, finds application in micro/nanofluidics, 7 flexible electronics, 8 and drag reduction surfaces. 7 Several research groups have shown both experimentally and numerically that unidirectionally textured substrates lead to anisotropic spreading, where liquids spread preferentially in the direction parallel to the texture.…”

“…The ability to create anisotropic spreading in particular, which enables liquid spreading to occur in a user-specified direction, finds application in micro/nanofluidics, flexible electronics, and drag reduction surfaces . Several research groups have shown both experimentally and numerically that unidirectionally textured substrates lead to anisotropic spreading, where liquids spread preferentially in the direction parallel to the texture. − Anisotropic spreading on unidirectionally textured substrates is most commonly explained by texture peaks, which impose a mechanical barrier that effectively “pins” the three-phase (solid/liquid/gas) contact line of the spreading liquid, inhibiting spreading in the direction perpendicular to the texture. − ,− The texture peaks are often described as energetic barriers that oppose wetting, which Yong and Zhang attribute to a high local atomic density at texture peaks, based on the results of molecular dynamics (MD) simulations (texture height of 1.85-23.77 Å).…”

Multiscale Modeling of the Three-Dimensional Meniscus Shape of a Wetting Liquid Film on Micro-/Nanostructured Surfaces

“…Checco and co-workers , measured the meniscus shape of thin organic liquid films (∼5 nm thick ethanol and octane films) on a nonwettable surface with wettable nanostripes using amplitude modulation atomic force microscopy (AM-AFM) in the noncontact regime. Fukuzawa et al measured the meniscus shape of a perfluoropolyether lubricant film with a thickness of a few nanometers on a silicon surface with oxide nanostructures using AFM. Seemann et al used AFM to measure the wetting morphologies of polystyrene on silicon microstructures.…”