Page 115 - Handbook of Surface Improvement and Modification

110 Surface Tension and Wetting

Figure 7.16. The photocleavage of SiO -NBS-F nanoparticles under UV irradiation. [Adapted, by permission,
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from Lin, B; Zhou, S, Appl. Surf. Sci., 359, 380-7, 2015.]
the amount of glycosaminoglycans on poly(3,4-ethylenedioxythiophene) surface can be
controlled in situ by electrical stimulus, and used to manipulate the osteogenic activity of
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Ti-6Al-4 V.
Wettability can also be controlled by light-responsive silica nanoparticles incorpo-
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rated in highly hydrophilic fluorocarbon coatings. A light-responsive silane coupling
agent was grafted on silica nanoparticles and bound by a click reaction (Figure 7.15). 34
The nanoparticles exhibited considerable change of wettability from near-superhydropho-
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bicity to near-superhydrophilicity after UV irradiation. After incorporation into fluoro-
carbon FEVE coating at small concentration (5 wt%), they resided on surface because of
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their low surface free energy. The coating wettability was changed from hydrophobicity
o
o
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(contact angle 106.4 ) to hydrophilicity (33.3 ) on UV irradiation. The photocleavage of
modified silica nanoparticles under UV irradiation (Figure 7.16) caused elimination of
hydrophobic nonafluorohexane segments from the silica surface on exposure to UV irradi-
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ation. The hydrophilic carboxyl groups were formed on the silica surface, leading to the
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transition from hydrophobicity to hydrophilicity.
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Nanoparticles assembly provide wettability for bio-inspired materials. The build-
ing blocks spontaneously organize themselves into ordered structures through thermody-
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namic processes. The review paper provides the information on the influence of
assemblies on wettability of materials as a spin-off knowledge from observation of
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nature.