Reversibly Light-Switchable Wettability of Hybrid Organic/Inorganic Surfaces With Dual Micro-/ Nanoscale Roughness

Advanced Functional Materials (Impact Factor: 11.81). 04/2009; 19(8):1149. DOI: 10.1002/adfm.200800909


Here, an approach to realize “smart” solid substrates that can convert their wetting behavior between extreme states under selective light irradiation conditions is described. Hybrid organic/inorganic surfaces are engineered by exploiting photolithographically tailored SU-8 polymer patterns as templates for accommodating closely packed arrays of colloidal anatase TiO2 nanorods, which are able to respond to UV light by reversibly changing their surface chemistry. The TiO2-covered SU-8 substrates are characterized by a dual micro-/nanoscale roughness, arising from the overlapping of surfactant-capped inorganic nanorods onto micrometer-sized polymer pillars. Such combined architectural and chemical surface design enables the achievement of UV-driven reversible transitions from a highly hydrophobic to a highly hydrophilic condition, with excursions in water contact angle values larger than 100°. The influence of the geometric and compositional parameters of the hybrid surfaces on their wettability behavior is examined and discussed within the frame of the available theoretical models.

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    • "Phase segregation is particularly detrimental not only for the expected bulk properties of the composite, which are the result of careful design of the matrix-filler mixture [8] [9], but also for their surface. In fact, may the composite be a coating or a bulky piece, the surface roughness is one of the most important properties to be controlled, affecting e.g. the lifetime of lubricating surfaces or the wetting properties of self-cleaning materials [10]. "
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    • "Several methods to prepare wettability contrast patterns have been reported, including the selective ultraviolet (UV) degradation of photocatalytic coatings [10] [11] [12] [13] [14], laser irradiation [15], inkjet printing [16], the adhesive tape method [17] and the soft lithography process [18] [19]. In the aforementioned methods, UV radiation combined with a photomask is the most popular and effective method, which can fabricate complex wettability contrast patterns. "
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    ABSTRACT: An atmospheric-pressure plasma jet (APPJ) has been developed to fabricate hydrophilic patterns on superhydrophobic surfaces. The surface morphologies, chemical compositions and wettability were investigated using scanning electron microscopy, Fourier-transform infrared spectrophotometry, X-ray photoelectron spectroscopy and water contact angle measurement. The results show that the superhydrophobic areas exposed to the APPJ could be completely converted to superhydrophilic without changing the macro and microsurface morphologies. The transition from superhydrophobicity to superhydrophilicity is because of the decrease of hydrophobic fluorine-containing functional groups and the increase of the hydrophilic oxygen-containing functional groups. Combined with scanning and mask technology, complex and large-area wettability contrast patterns can be easily fabricated on various superhydrophobic substrates by the APPJ treatment. Additionally, the retention of intrinsic microstructures enables the surface to recover superhydrophobicity only by using surface fluorination. This results in a rapid reversible transition between superhydrophilicity and superhydrophobicity.
    Full-text · Article · Feb 2015
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    • "SU-8 has been also used for the fabrication of dual-scale rough structures. Such hierarchical structures produced with SU-8 have been coated with titanium dioxide, PTFE submicrometer particles and fluorocarbons in order to obtain surfaces with special wetting properties [19] [20] [21]. "

    Full-text · Chapter · Jul 2013
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