Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, Chicago, IL 60607, USA.
Nanoscale. 2012 Sep 7;4(17):5378-85. doi: 10.1039/c2nr30979c. Epub 2012 Jul 23.
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.
具有交替（二元）超疏水-超亲水区域的表面可以在自然界中找到，为高效流体收集和管理技术提供了受生物启发的模板。我们描述了一种简单的湿法处理、热处理方法来生产这种图案，从通过喷雾铸造纳米颗粒分散体制备的固有超疏水聚硅倍半氧烷-二氧化硅复合涂层开始。通过激光辐照或暴露在开放空气中进行局部热处理后，这些涂层会变得超亲水。当进行激光处理时，薄膜可以图案化到约 100μm 的尺度。分散体由疏水性气相法二氧化硅 (HFS) 和甲基倍半硅氧烷树脂组成，分散在异丙醇中并沉积在各种基底（玻璃、石英、铝、铜和不锈钢）上。通过在热处理前后进行前进、后退和静止接触角测量来对涂层润湿性进行特征描述，以阐明 HFS 填料浓度和热处理对涂层润湿性的影响。SEM、XPS 和 TGA 测量揭示了热处理对表面化学和纹理的影响。用 Cassie-Baxter 润湿理论解释了从超疏水到超亲水的热诱导润湿性转变。几个微图案化的润湿性表面展示了在池沸腾传热增强、开放表面张力受限通道中的毛细驱动液体传输（例如，芯片上实验室）以及依赖润湿性梯度的选择性表面涂层应用中的潜力。本方法的优点包括基于有机硅烷的涂层固有的稳定性和惰性，它可以很容易地应用于许多类型的表面（玻璃、金属等）。本方法还可以扩展到大面积，因此对于工业涂层应用具有吸引力。
