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In-Depth Information
Figure 5.9
Five phases in the evolution of protrusions after the plasma
treatment by varying the etching powers and the etching times
[41].
Etching strategy was used to fabricate polymer-based
electrohydrodynamic spraying devices with superhydrophobic
nozzles, as reported by Byun et al. [42]. The nozzle was produced
from polyfluorotetraethylene (PTFE) while the superhydrophobicity
was created by roughening the surface of the PTFE with O
and Ar
ion beam plasma. The surface exposed to the beam for just 10 min
exhibited contact angles greater than 160
2
°
which was due to the
appearance of nanoscale structures having the width and height of
∼
µ
m, respectively. These superhydrophobic nozzles
could sustain their high contact angles for as long as two months,
and the jetting was stable.
Lithography followed by plasma etching is the main top-down
approach for micro- and nanopatterning [43]. Accardo et al. reported
the fabrication of superhydrophobic PMMA surfaces having contact
angle of
200 nm and 1.2
∼
°
with high optical and X-ray transparency through
the use of optical lithography and plasma etching [44]. O
170
-Ar
plasma was used for this surface etching and, it was found that, a
hybrid-etch process based on this gas mixture leading to both an
ion-enhanced chemical and a physical sputter etching. The treated
surfaces contained either a microscale pattern of micropillars or a
random nanofibrillar pattern. Interestingly, nanoscale asperities
on top of the micropillar morphology closely resembled
2
Nelumbo
nucifera
, lotus leafs.
Combination of plasma etching with other strategies
was generally done. Balu et al. demonstrated the creation of
superhydrophobic surface on cellulose paper by selective etching of
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