| Recently, superhydrophobic surfaces with water contact angles larger than 150°have received a lot of attention, due to their important application ranging from self-cleaning materials, microfluidic devices to biomaterials. The archetype of a natural superhydrophobic surface is the lotus leaf, on which a water droplet apparently forms the shape of a pearl and roll off very easily, so dirt is easily removed with a rain shower.Water repellency on solid materials is not only a chemical origin, but also the microtextured. In order to fabricate a superhydrophobic surface, we discussed the two theories of superhydrophobic states: the Wenzel state and Cassie state. By design the proper geometrical parameters of arrays of pillars, we got superhydrophobic surface, and compared measured data with theory data. To keep the stability of superhydrophic state, it requires smaller feature size that is highly larger vertical height and smaller spacing for regular arrays of pillars.As a newly coming micro-fabrication technology, soft lithography use elastomeric stamp in stead of hard stamp in traditional lithography to fabricate micro patterns and structures. Compared with traditional lithography, soft lithography has several unique advantages. Firstly, it can apply in multi materials and chemical surfaces. Secondly, it can fabricate complicated 3D structure even on curved surfaces and of large areas. In addition, it can overcome the 100nm obstacle of lithography, and pattern features with dimension <100nm, realize much more elaborate microfabrication. Now, soft lithography is widely applied in various fields including the fabrication optics, biotechnology, microelectronics, sensors and micro total analysis systems (μ-TAS).In this paper, we introduced soft lithography and its critical techniques, and fabricated the vital element of elastomeric stamp with polydimethylsiloxane (PDMS). We use typical replica molding (RM) to fabricate arrays of periodic pillars. The microscopy images demonstrate the high fidelity and facility of RM for microstructure fabrication process.To evaluate the effect of super-hydrophobic and textured surfaces on blood compatibility, dynamic clotting time, hemolysis rate and platelet adhesion test were carried out. The results show that: the dynamic clotting time is prolonged when the surface is superhydrophobic. Observing hemocyte variation, the hemolysis rate of all the samples was below 5%, and as the surface is more hydrophobic, the hemolysis rate was a little decreased. The morphology of platelets attached on smooth surface, spreading flattened and aggregated. On arrays of micro-pillars surfaces, it has a less platelet adhesion, especially when the surface is super hydrophobic. Also, for patterned submicro-grooves surface, it was clear of platelet and keeped a normal shape, no significant pseudopodium and aggregation was found. Surfaces combined proper patterns and hydrophobias, could prevent the adhesion and activation of platelet to some extent. The blood compatibility of the textured fabrics with appropriate hydrophobe is improved compared with smooth surface.It is a hot issue to reduce drags and save a large mount of energy. Design low-drag surface and make deeper research about a micro fluid of how to decrease drag have important practical meanings. Researches have demonstrated that on superhydrophobic non-smooth surface can reduce the drag. So we fabricated periodic grooves patterns on Si wafer with femtosecond laser. The texutrued surfaces were silanized and became superhydrophobic. We investigated the flow of 60% glycerin solution on such superhydrophobic groove surfaces with a commercial rheometer. A superhydrophobic groove surfaces has been shown to generate an effective liquid drag reduction because of the air trapped between the surface structures, and the maximal slip length obtained by computing according to our equation and experimental data is 220μm. A slip over superhydrophobic surfaces makes an effective drag reduction. |
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