Graduate Student Amir Zahmatkeshsaredorahi

"Superhydrophobic surfaces: Preparation, properties assessment and application"

One of the main goals in science has always been finding ways to understand nature. Inspired by the surface properties of Lotus leaf, scientists started to develop superhydrophobic surfaces. In this seminar, wet ability of surfaces is reported, using Young, Wenzel, and Cassie-Baxter equations for homogenous and heterogeneous solid surfaces. Moreover, the effects of the surface morphology on hydrophobicity have been investigated.[1]

Synthesizing core-shell Fe3O4@SiO2 nanoparticles and functionalizing with cetyl trimethyl ammonium bromide (CTAB) was accomplished by Zhou et al. [2] A multiple hybrid coating method with an Epoxy resin as adhesive layer has been used. The resulting surfaces showed water contact angles (WCA) of 174.5°. Due to super hydrophobicity, the resulting coated layer acted as a barrier between the electrolyte and the anode in 3.5 wt.% NaCl solution and improved the corrosion resistance of Q235 steel to 1.6 × 10-7 mm/year.

Using a similar method of fabrication, Xiaojing Su et al. [3] used fluoroalkylsilane (FAS) as a surface modifier to obtain modified Fe3O4 nanoparticles. Due to the ferrimagnetic behavior of Fe3O4, a magnetic field has been used to fabricate asymmetrical roll down/pinned state superhydrophobic surfaces on fabric fibers with WCA of 165° and sliding angles (SA) of 7.5° on roll the down state and WCA of 152° and SA of 180° on the pinned state.

One of the biggest disadvantages of SHS has always been vulnerability to mechanical damage. Shengyang pan et al. [4] fabricated SHS using a shape memory micro pillar array decorated by pH responsive capsules encapsulated with fluoroalkylsilane. The resulting surfaces showed dual self-healing properties, both self-repairing the microstructure by heat and retreating the surface chemistry with releasing the FAS capsules in response to acid stimuli.

(1) H. Yildirim Erbil and C. Elif Cansoy Range of Applicability of the Wenzel and Cassie-Baxter Equations for Superhydrophobic Surfaces, Langmuir, 2009, 25(24), 14135–14145.

(2) Yaya Zhou, Yibing Ma, Youyi Sun, Zhiyuan Xiong, Chunhong Qi, Yinghe Zhang, and Yaqing Liu, Robust Superhydrophobic Surface Based on Multiple Hybrid Coatings for Application in Corrosion Protection ACS Applied Materials & Interfaces 2019, 11, 6512−6526.

(3) Xiaojing Su, et al, Dual-Functional Superhydrophobic Textiles with Asymmetric Roll Down/Pinned States for Water Droplet Transportation and Oil−Water Separation, ACS Applied Materials & Interfaces 2018, 10, 4213−4221.

(4) Shengyang Pan, Min Chen, and Limin Wu, Smart Superhydrophobic Surface with Restorable Microstructure and Self-Healable Surface Chemistry, ACS Applied Materials & Interfaces 2020, 12, 5157−5165.