Samanta Avik, Huang Wuji, Chaudhry Hassan, Wang Qinghua, Shaw Scott K, Ding Hongtao
Department of Mechanical Engineering, University of Iowa, Iowa City, Iowa 52242, United States.
Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, United States.
ACS Appl Mater Interfaces. 2020 Apr 15;12(15):18032-18045. doi: 10.1021/acsami.9b21438. Epub 2020 Apr 3.
Extreme wetting activities of laser-textured metal alloys have received significant interest due to their superior performance in a wide range of commercial applications and fundamental research studies. Fundamentally, extreme wettability of structured metal alloys depends on both the surface structure and surface chemistry. However, compared with the generation of physical topology on the surface, the role of surface chemistry is less explored for the laser texturing processes of metal alloys to tune the wettability. This work introduces a systematic design approach to modify the surface chemistry of laser textured metal alloys to achieve various extreme wettabilities, including superhydrophobicity/superoleophobicity, superhydrophilicity/superoleophilicity, and coexistence of superoleophobicity and superhydrophilicity. Microscale trenches are first created on the aluminum alloy 6061 surfaces by nanosecond pulse laser surface texturing. Subsequently, the textured surface is immersion-treated in several chemical solutions to attach target functional groups on the surface to achieve the final extreme wettability. Anchoring fluorinated groups (-CF- and -CF) with very low dispersive and nondispersive surface energy leads to superoleophobicity and superhydrophobicity, resulting in repelling both water and diiodomethane. Attachment of the polar nitrile (-C≡N) group with very high nondispersive and high dispersive surface energy achieves superhydrophilicity and superoleophilicity by drawing water and diiodomethane molecules in the laser-textured capillaries. At last, anchoring fluorinated groups (-CF- and -CF) and polar sodium carboxylate (-COONa) together leads to very low dispersive and very high nondispersive surface energy components. It results in the coexistence of superoleophobicity and superhydrophilicity, where the treated surface attracts water but repels diiodomethane.
激光织构金属合金的超润湿性因其在广泛商业应用和基础研究中的卓越性能而备受关注。从根本上讲，结构化金属合金的超润湿性取决于表面结构和表面化学性质。然而，与表面物理拓扑结构的生成相比，在金属合金激光织构过程中，表面化学性质对润湿性调节作用的研究较少。本工作引入了一种系统设计方法，用于改变激光织构金属合金的表面化学性质，以实现各种超润湿性，包括超疏水/超疏油、超亲水/超亲油以及超疏油与超亲水共存。首先通过纳秒脉冲激光表面织构技术在6061铝合金表面制备微尺度沟槽。随后，将织构化表面浸入几种化学溶液中，使目标官能团附着在表面，以实现最终的超润湿性。锚定具有极低色散和非色散表面能的氟化基团（-CF-和-CF）会导致超疏油和超疏水性能，从而排斥水和二碘甲烷。附着具有非常高非色散和高色散表面能的极性腈基（-C≡N），通过在激光织构的毛细管中吸引水分子和二碘甲烷分子，实现超亲水和超亲油性能。最后，同时锚定氟化基团（-CF-和-CF）和极性羧酸钠（-COONa）会导致极低的色散表面能成分和非常高的非色散表面能成分。这导致超疏油和超亲水性能共存，即处理后的表面吸引水但排斥二碘甲烷。
