Biomedical Engineering Reference
In-Depth Information
9.3.3.1
Combination Methods Based on Chemical Vapor Deposition
Sun et al. [
127
] have utilized CVD to fabricate superhydrophobic film with
anisotropically ACNTs with uniform tube length on quadrate micropillar arrays
silicon substrates produced by photolithography. Due to the anisotropic nature of the
carbon nanotube (CNT) arrays, both hydrophobic and hydrophilic surfaces coexist
depending on the spacing between the pillar arrays. However, after further coating
with a fluorinated SAM of (2-(perfluorooctyl)ethyl)trimethoxysilane, all surfaces
turned to be superhydrophobic without the spacing effects.
Zhu et al. [
128
] also used CVD to grow CNT arrays on micro-patterned silicon
wafers and nanoscaled CNT films, creating surfaces with two-scale roughness, to
compare the wetting properties. As for the CNT arrays on CNT films, the size,
pitch, and height are varied to explore their effects on the hydrophobicity of the
surfaces. The results suggest that the micro-scale roughness determines the WCA
since the nanoscale roughness does not significantly increase the WCA compared
to micro-patterned silicon surfaces with similar geometrical sizes. However, the
nanoscale roughness can lower the contact angle hysteresis to less than 1
ı
and refine
the stability of the superhydrophobic surfaces.
9.3.3.2
Combination Methods Based on Membrane Casting
Most porous polymer membranes are produced by casting polymer solution through
an appropriate template, with microscopic structures formed by phase separation,
which occurs when the polymer solution approaching the cloud point is immersed
in nonsolvents or experiences heat treatments. The nucleation of polymer results
in rich poor phases of polymer due to the interaction of solvent and nonsolvents
with macromolecules. The macromolecules nucleate and the networks form in the
polymer-rich phase whereas pores form after the solvent removal in the polymer-
poor phase [
129
].
Erbil et al. [
130
] have used isotactic polypropylene (i-PP) to prepare superhy-
drophobic surfaces by changing solvents, nonsolvents, solute concentration as well
as drying temperature. The results show that decreasing the drying temperature
promotes a loose network formation and methyl ethyl ketone is the best nonsolvent,
generating a surface with contact angle of 160
ı
.
Basedontheabovework,Luetal.[
131
] used LDPE to prepare superhydrophobic
surfaces through thermally induced phase separation. The structure and thus the
wettability of the ultimate film can be controlled by changing the endurance time of
heat treatment.
Super-amphiphobic surfaces are achieved by Xie et al. [
132
] with coating by two
polymeric materials: poly(methyl methacrylate) (PMMA) and fluorine-end-capped
polyurethane (FPU). Films containing only PMMA exhibit water CA of 145
ı
and
rough structures with micropapillae. Films with the mixture of PMMA and FPU
