Laney Sophia K, Michalska Martyna, Li Tao, Ramirez Francisco V, Portnoi Mark, Oh Junho, Thayne Iain G, Parkin Ivan P, Tiwari Manish K, Papakonstantinou Ioannis
Photonic Innovations Lab, Department of Electronic & Electrical Engineering, University College London, Torrington Place, London WC1E 7JE, U.K.
Nanoengineered Systems Laboratory, Department of Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE, U.K.
Langmuir. 2021 Aug 24;37(33):10071-10078. doi: 10.1021/acs.langmuir.1c01310. Epub 2021 Jul 21.
Slippery liquid infused porous surfaces (SLIPS) are an important class of repellent materials, comprising micro/nanotextures infused with a lubricating liquid. Unlike superhydrophobic surfaces, SLIPS do not rely on a stable air-liquid interface and thus can better manage low surface tension fluids, are less susceptible to damage under physical stress, and are able to self-heal. However, these collective properties are only efficient as long as the lubricant remains infused, which has proved challenging. We hypothesized that, in comparison to a nanohole and nanopillar morphology, the "hybrid" morphology of a hole within a nanopillar, namely a nanotube, would be able to retain and redistribute lubricant more effectively, owing to capillary forces trapping a reservoir of lubricant within the tube, while lubricant between tubes can facilitate redistribution to depleted areas. By virtue of recent fabrication advances in spacer defined intrinsic multiple patterning (SDIMP), we fabricated an array of silicon nanotubes and equivalent arrays of nanoholes and nanopillars (pitch, 560 nm; height, 2 μm). After infusing the nanostructures (prerendered hydrophobic) with lubricant Krytox 1525, we probed the lubricant stability under dynamic conditions and correlated the degree of the lubricant film discontinuity to changes in the contact angle hysteresis. As a proof of concept, the durability test, which involved consecutive deposition of droplets onto the surface amounting to 0.5 L, revealed 2-fold and 1.5-fold enhancements of lubricant retention in nanotubes in comparison to nanopillars and nanoholes, respectively, showing a clear trajectory for prolonging the lifetime of a slippery surface.
注入滑液的多孔表面（SLIPS）是一类重要的疏水材料，由注入润滑液的微/纳米纹理组成。与超疏水表面不同，SLIPS不依赖稳定的气液界面，因此能更好地处理低表面张力流体，在物理应力下更不易受损，且能够自我修复。然而，只有在润滑剂保持注入状态时，这些综合特性才有效，而这已被证明具有挑战性。我们推测，与纳米孔和纳米柱形态相比，纳米柱内孔的“混合”形态，即纳米管，能够更有效地保留和重新分配润滑剂，这是由于毛细力将润滑剂储存在管内，而管间的润滑剂有助于将其重新分配到耗尽区域。借助间隔定义固有多重图案化（SDIMP）的最新制造进展，我们制造了一系列硅纳米管以及等效的纳米孔和纳米柱阵列（间距560纳米；高度2微米）。在用润滑剂Krytox 1525注入纳米结构（预先制成疏水结构）后，我们探究了动态条件下润滑剂的稳定性，并将润滑膜不连续程度与接触角滞后的变化相关联。作为概念验证，耐久性测试包括在表面连续沉积总计0.5升的液滴，结果表明，与纳米柱和纳米孔相比，纳米管中润滑剂保留率分别提高了2倍和1.5倍，这为延长光滑表面的寿命指明了一条清晰的路径。
