Chongqing University of Science and Technologies, Chongqing 400030, China.
Institute of Advanced Manufacturing Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Changzhou, 213164, China.
Langmuir. 2021 Feb 23;37(7):2312-2321. doi: 10.1021/acs.langmuir.0c03122. Epub 2021 Feb 5.
In nature, many plants have evolved various wettability surfaces to survive and thrive in diverse environments. For example, the superhydrophobic surface of lotus can keep itself clean, while the rose petals can retain droplets for a long time. The former is referred to the "lotus effect," and the latter is known as the "rose petal effect." This research proposes a method to fabricate magnetic-responsive superhydrophobic magnetorheological elastomers (MREs) which could reversibly and instantly transition their surface wetting state between the "lotus effect" and the "rose petal effect." These surfaces with controllable wettability could find applications in the manipulation of liquids in biological and chemical systems. The MREs are cured by applying a uniform magnetic field to form "mountain-like" microstructures on their surfaces. This initial surface is rough and exhibits the lotus leaf effect. Because of the nonuniform magnetically induced deformation, the surface micromorphology and roughness can be altered by an applied magnetic field. The state of water droplets on its surface is changed from the Wenzel state to the Cassie-Baxter (CB) state. Therefore, the proposed MRE surface could switch their dynamic wetting features between the "rose petals" and "lotus leaves" via a magnetic field. An experimental platform for the wetting features of MRE surfaces is established to characterize the dynamic behaviors of water drops on MREs under a magnetic field. A magneto-mechanic coupled model is proposed to interpret how the magnetic field influences the MRE surface as well as the droplet movement.
在自然界中，许多植物已经进化出各种不同的润湿性表面，以在不同的环境中生存和繁衍。例如，荷叶的超疏水表面可以保持自身清洁，而玫瑰花瓣可以长时间保留液滴。前者被称为“荷叶效应”，后者则被称为“玫瑰花瓣效应”。本研究提出了一种制造磁响应超疏水磁流变弹性体（MRE）的方法，这种 MRE 可以在“荷叶效应”和“玫瑰花瓣效应”之间可逆且瞬时地转变其表面润湿性状态。这些具有可控润湿性的表面可以在生物和化学系统中液体的操纵方面得到应用。MRE 是通过施加均匀磁场固化形成的，在其表面形成“山状”微观结构。这种初始表面是粗糙的，表现出荷叶效应。由于非均匀磁致伸缩变形，表面微形态和粗糙度可以通过施加磁场来改变。其表面上的液滴状态从 Wenzel 状态转变为 Cassie-Baxter（CB）状态。因此，通过磁场，所提出的 MRE 表面可以在“玫瑰花瓣”和“荷叶”之间切换其动态润湿特性。建立了用于 MRE 表面润湿特性的实验平台，以表征磁场下 MRE 上液滴的动态行为。提出了一种磁-力学耦合模型，以解释磁场如何影响 MRE 表面以及液滴的运动。
