Study On Preparation And Properties Of Superhydrophobic Surfaces With Tunable Adhesion

Superhydrophobic surfaces are not only applied in fundamental researches, but also in many fields, such as anti-corrosion, anti-pollution, transportation with no loss and so forth due to their special wettability. Adhesive property is one of most important physical properties, because it can directly determine dynamic behavior of water droplets on the superhydrophobic surface. But in fact, it has attracted little attention. Recent years, more attentions are occurred in superhydrophobic surfaces with high contact angle and low sliding angle, rather than superhydrophobic surfaces with high adhesion and tunable adhesion. Therefore, this paper describes some superhydrophobic surfaces with nano-micro constructure and illustrates the influences on superhydrophobicity and adhesiveness from the surface chemical composition and surface morphology.The main research contents and conclusions are as follows:1. Hydrophobic ZnO nanoparticles are obtained through a simple liquid-phase reaction between stearic acid and hydrophilic ZnO nanoparticles. Then the mixtures of hydrophilic/hydrophobic ZnO nanoparticles are added in the absolute ethanol according to certain proportions, the resulting suspensions are sprayed onto substrates to form superhydrophobic ZnO surfaces. The adhesion on superhydrophobic surface can be tuned by controlling the proportion of hydrophilic/hydrophobic ZnO nanoparticles. Water contact angles on the superhydrophobic surfaces are higher than150°. Sliding angle changes from 90° to 2° and the adhesive force varies from 111.6μN to 2.5 μN.2. ZnO surfaces with tunable morphologies have been fabricated by hydrothermal process via changing reaction time, reaction temperature and concentration ratio. After the further modification of stearic acid, superhydrophobic surfaces with tunable adhesion are obtained.3. ZnO superhydrophobic surface with low adhesion is obtained by the spray-process. Low adhesion of superhydrophobic surface is successfully changed to high adhesion of that after UV irradiation, then low adhesive property is obtained again during annealing process. The reversible conversion between low adhesion and high adhesion can be undergone several times.4. Hydrophobic SiO₂ nanoparticles are obtained through a simple reaction between octadecyltrichlorosilane and hydrophilic Si O2 nanoparticles. Then the mixtures of hydrophilic/hydrophobic SiO₂ nanoparticles are added in the absolute ethanol according to certain proportions, the resulting suspensions are sprayed onto metal substrates to form superhydrophobic surfaces. The adhesion on superhydrophobic surface can be controlled by changing the proportion of hydrophilic/hydrophobic SiO₂ nanoparticles. With a decrease of hydrophilic SiO₂ nanoparticles and an increase of hydrophobic SiO₂ nanoparticles, water contact angles on the superhydrophobic surfaces are higher than 150° and sliding angle changes from 90° to 2°.5. Three kinds of Co surfaces with nano-sheet arrays have been fabricated on zinc substrates based on a simple chemical deposition method. After being modified with stearic acid, the wettability of the Co surfaces changes from hydrophilicity to superhydrophobicity. We regulate the solution-immersion process by changing the concentration of CoSO4 to control different topographies of Co surfaces. The water adhesion on the same superhydrophobic surface can be effectively tuned by dynamically controlling the topographies of microstructures without altering the surface composition.