Adjustable, (super)hydrophobicity by e-beam deposition of nanostructured PTFE on textured silicon surfaces

Abstract

Polytetrafluoroethylene (PTFE)-like films, produced by electron beam (e-beam) deposition, have shown higher hydrophobicity than those deposited by RF sputtering under similar deposition rates. It was found that this results from both surface chemical composition and nano-roughness. X-ray photoelectron spectroscopy measurements revealed that larger moieties of CF 2 and CF 3 groups were present to reduce surface energy in the e-beam deposited films. RF sputtering led to a higher degree of PTFE target fragmentation producing a different perfluorinated film on the Si substrate. Scanning electron microscopy and atomic force microscopy measurements revealed a much larger rms roughness on the film surfaces produced by e-beam (25.13 nm, at 20 mA) than those by RF sputtering (2.42 nm, at 100 W), and allowed a broad power spectrum density analysis with determination of the j B wetting parameter. In addition, the e-beam deposited films presented a linear increase of contact angle with applied electron current in the range under study (5-20 mA). This allows easy water repellency adjustment, up to 159 ± 2°. For a superhydrophobic state with self-cleaning, a micropyramid structure was wet etched on the Si wafer, followed by PTFE deposition, and a very low contact angle (163 ± 2°) and hysteresis was attained (\3°). These first results indicate that e-beam PTFE deposition with adjustable hydrophobicity may become a useful technique for integrated production with present Si microelectronics technology and for Si solar cells.

3D μ-printing of polytetrafluoroethylene microstructures: A route to superhydrophobic surfaces and devices

“…Various methods, including micromachining or microetching processes, have been demonstrated to create PTFE microstructures. However, either micromachining methods, such as templated hot embossing [8,9], cryogenically assisted abrasive jet [10], and roughening with sandpaper [11], or microetching processes, which use external energy to depolymerize PTFE into tetrafluoroethylene monomers and volatilize it into gas form, such as high-energy synchrotron radiation [12], laser-plasma X-ray [13], laser/femtosecond laser [14], and focused ion/proton/electron beam [15,16], which use external energy to depolymerize PTFE into tetrafluoroethylene monomers and volatilize it into gas form, can only produce 2D micropatterns or at most some 2.5D microstructures. Therefore, it still remains a challenge to flexibly fabricate 3D PTFE microstructures for practical applications.…”

Facile Adhesion-Tuning of Superhydrophobic Surfaces between “Lotus” and “Petal” Effect and Their Influence on Icing and Deicing Properties

“…The SH surfaces with the tunable adhesion forces have emerging applications in the field of controlled microdroplet transportation, biochemical separation, self-cleaning, deicing, cell adhesion/tissue engineering, , and vapor condensation and collection . A number of methods, such as electrodeposition, electromachining jet technique, e-beam deposition, linear templated texturing, femtosecond laser weaving, and heterogeneous chemical composition (mixture of hydrophobic and hydrophilic compounds), have been explored to control adhesion of SH surfaces. , Besides, the use of PDMS in fabricating SH surfaces with controlled adhesion includes PDMS microcell array, femtosecond parallel array, and other 3D pattern dependent structures . However, most of these methods require the use of expensive facilities and fabrications which are not scalable for industrial level.…”

Antimicrobial 3D Porous Scaffolds Prepared by Additive Manufacturing and Breath Figures

“…[27] Breath figures will enable the formation of porous surfaces by evaporation of a polymer solution in a moist atmosphere. While, several methodologies have been employed including solvent casting, spin coating or dip coating to fabricate planar porous surfaces [30][31][32][33][34][35][36], examples about the preparation of non-planar surfaces are scarce. [37][38][39][40] Moreover, to the best of our knowledge there is no precedent in the fabrication of breath figures at the surface of complex geometries obtained by additive manufacturing.…”