Research On The Preparation And Applications Of Biomimetic Superhydrophobic Materials

Nature has long served as a source of inspiration for scientists and engineers. Inspired from lotus leaf, a variety of biomimetic surfaces with superhydrophobicity have been fabricated in recent years based on the combination of surface micro-and nanostructures and chemical compositions by using many different synthetic methods. With the deep investigation on this field, the research point tends to the application of biomimetic superhydrophobic surfaces. In this regard, it is necessary to expand the superhydrophobic materials to practical applications. The main content and conclusion are listed as follows:(1) A simple approach is used to creating bifunctional Fe3O4/polydopamine (Fe3O4/PD) composite nanoparticles (NPs) with both superparamagnetic and superhydrophobic properties. The Fe3O4/PD NPs are prepared by virtue of dopamine self-polymerization under mild conditions. The Fe3O4/PD NPs have uniform sizes in a narrow range of100～300nm. Magnetic measurement revealed the Fe3O4/PD NPs are superparamagnetic with saturation magnetization of73.40emu/g. The as-prepared particles show superhydrophobicity after being modified by1H,1H,2H,2H-perfluorodecyltrichlorosilane. The Fe3O4particles are also modifiedby fluoroalkylsilane, and the surface composed of the particles present a water contact angle (CA) of117°, indicating that plenty of phenolic hydroxyl groups in polydopamine may promote the modification of fluorosilane for the surface of Fe3O4. The magnetic liquid marble is obtained by coating some superhydrophobic Fe3O4/PD NPs on a water droplet. The CA of a liquid marble (4μL) on the hydrophilic slide glass is164°, and the sliding angle is8°. Meanwhile, the mechanical strength and robustness of the liquid marbles are demonstrated. The liquid marbles are effortlessly controlled to move on various surfaces, such as flat surfaces, curved surfaces, in oil phase under an external magnetic field control. These results indicated that the magnetic liquid marbles are effective applications for manipulation of liquid transport in microfluidic devices. The surface composed by the Fe3O4/PD NPs has a water CA more than150°, while the CA of oil is nearly0°. Therefore, these particles can be used to oil/water separation and the separated oil can be easily transport in the water with an external magnetic field. Importantly, the particles can be simply retrieved on the basis of their superparamagnetic property. Moreover, the reclaimed Fe3O4/PD NPs after washed and dried can still be superhydrophobicity and can be used repeatedly.(2) A facile and industrialized route is presented to prepare aligned TiO2nanotubes-coated titanium mesh, which show special wettability after being modified by perfluorosilane, which shows excellent superhydrophobicity with water a contact angle of162°and impermeability to water owing to the large negative capillary effect. However, the same mesh film exhibits superoleophilicity with oil water contact of nearly0°and good permeability to oil owing to the capillary effect. It was proved that the as-prepared titanium mesh is employed to effectively separate the mixture of oil and water with a high separation efficiency, which reaches up to99%. After oil/water separation for20times, the mesh remain superhydrophobicity and a high separation efficiency for separation. In addition, the mesh has a good stability in corrosive liquids with pH value of1to14for12h.(3) A general and simple route is used to be fit for fabricating superhydrophobic/superoleophilic porous materials via an oxidative chemical polymerization of aniline and modification of thiols. Based on this method, aniline monomers are polymerized into polyaniline (PANI) nanofibers, which are deposited onto the fabric fiber. The PANI nanofibers largely enhance surface roughness of original fabric. After the modification with n-octadecyl thiol, the water repellent fabrics are obtained. Interestingly, the as-prepared fabrics show stable high hydrophobicity towards many corrosive solutions (acidic, basic, salt liquids), hot water, and mechanical abrasion. Therefore, the excellent stability of the superhydrophobicity fabrics strongly extends applications in the realistic environment, even in the harsh condition. Additional, it was proved that this method is also applied to other porous materials with different pore diameter and chemical compositions, for instance, stainless steel meshes with different pore diameter and sponges. More importantly, the as-obtained diverse superhydrophobic/superoleophilic porous materials were successfully and effectively achieve to separate the oil-and-water mixture. Among them, the superhydrophobic PANI-coated sponge can absorb a broad variety of oils with enormous absorption capacities and excellent recyclability, no water droplet adhesion totally.(4) A Ag-coated copper mesh film with the property of pH-controllable water permeation is fabricated by a simple and fast, inexpensive, low power, environment-friendly solution-immersion method. For an acidic or a neutral droplet, the as-prepared film is superhydrophobicity with a CA of160°, and the droplet cannot penetrate into the film due to the large negative capillary effect. However, for a basic droplet, the mesh film is superhydrophilicity, and the droplet can penetrate into the film easily. Moreover, the mesh film can repeat six times transition between superhydrophobicity and superhydrophilicity. It was proved that the smart water permeation can be freely controlled by easily adjusting the solution pH.