Superhydrophobic–superhydrophilic binary micropatterns by localized thermal treatment of polyhedral oligomeric silsesquioxane (POSS)–silica films

Abstract

Surfaces patterned with alternating (binary) superhydrophobic-superhydrophilic regions can be found naturally, offering a bio-inspired template for efficient fluid collection and management technologies. We describe a simple wet-processing, thermal treatment method to produce such patterns, starting with inherently superhydrophobic polysilsesquioxane-silica composite coatings prepared by spray casting nanoparticle dispersions. Such coatings become superhydrophilic after localized thermal treatment by means of laser irradiation or open-air flame exposure. When laser processed, the films are patternable down to ∼100 μm scales. The dispersions consist of hydrophobic fumed silica (HFS) and methylsilsesquioxane resin, which are dispersed in isopropanol and deposited onto various substrates (glass, quartz, aluminum, copper, and stainless steel). The coatings are characterized by advancing, receding, and sessile contact angle measurements before and after thermal treatment to delineate the effects of HFS filler concentration and thermal treatment on coating wettability. SEM, XPS and TGA measurements reveal the effects of thermal treatment on surface chemistry and texture. The thermally induced wettability shift from superhydrophobic to superhydrophilic is interpreted with the Cassie-Baxter wetting theory. Several micropatterned wettability surfaces demonstrate potential in pool boiling heat transfer enhancement, capillarity-driven liquid transport in open surface-tension-confined channels (e.g., lab-on-a-chip), and select surface coating applications relying on wettability gradients. Advantages of the present approach include the inherent stability and inertness of the organosilane-based coatings, which can be applied on many types of surfaces (glass, metals, etc.) with ease. The present method is also scalable to large areas, thus being attractive for industrial coating applications.

Enhanced pool-boiling heat transfer on laser-made hydrophobic/superhydrophilic polydimethylsiloxane-silica patterned surfaces

“…4(a)]. Very comparable results can be found in a paper by Schutzius, et al [24], where they studied the wettability transition during the thermal treatment of a methylsilsesquioxane-silica coating. Fig.…”

“…5(a), is relatively smooth compared to the coated foils. Introducing the hydrophobic silica particles into the coating therefore results in a hierarchical micro-and nano-roughened surface, which was already shown to exhibit highly hydrophobic, or even superhydrophobic, properties [24,25].…”

Analysis of wear abrasion resistance of superhydrophobic acrylonitrile butadiene styrene rubber (ABS) nanocomposites

“…They are frequently used as thickening agent and viscosity stabilizer in cosmetics, toothpastes, food additives, antiperspirant sprays, medicines, paints, coatings, printing inks, adhesives, etc. Lately, HMFS combined with different organic materials has been used for spray deposition of nanocomposite superhydrophobic coatings for various substrates [51,52]. Their unique agglomeration pattern characteristics in polymer matrices provide the desirable hierarchical morphology comprising both micro-and nano-meter scale roughness typically required for superhydrophobic wetting behavior.…”

A universal method to create surface patterns with extreme wettability on metal substrates

“…These surfaces have been intensely investigated in different domains thanks to their wide applications in various technical areas such as drag reduction [5], self-cleaning [6][7], anti-icing [8][9][10], anti-corrosion [11][12], oil/water separation [13][14], etc. Extreme wettability patterns refer to surfaces containing both superhydrophobic and superhydrophilic regions, and these properties enable the control of fluids that are water-based, which have been widely applied in modern science and technology, such as cell growth [15], manipulation of egg quality [16], determination of biomolecules [17] in biotechnology, microfluidic localization in microfluidics, control and mixing of liquid geometry [18][19], lithography [20], etc.…”