Highly Transparent And Super-omniphobic Surface Fabricated By Phase Separation Of Polymer Blends

As a new type of functional surface,super-omniphobic surface shows great application potential in the fields of fluid drag reduction,high-definition display equipment,biomedical devices and so on.Especially in the application fields of optical lenses and interactive systems,super-omniphobic property has become an important and challenging new index.Nowadays,the fabrication of super-omniphobic surface has been widely studied,which can be realized by increasing the roughness of the surface and constructing the re-entrant curvature.However,at present,most of the existing rough surfaces or re-entrant structure can only achieve high repellency for liquids with high surface tension,such as water,but they are hardly super-omniphobic for liquids with low surface tension,such as oleic acid and hexadecane,which limits their application space in real scenes.On the other hand,in the application fields such as optoelectronic devices and wearable devices,people put forward higher requirements for the transparency of super-omniphobic surfaces.The structures fabricated on the surface often scarify the transparency.Especially when the ordered micron structure is introduced,it will make a strong iridescent effect to the surface,which limits the application of super-omniphobic surface in self-cleaning lens and transparent display equipment.In addition,the existing manufacturing technology of super-omniphobic surface are often inefficient and the area of the finished product is small,which is difficult to put into practical application.Based on this,how to prepare a new functional surface with both transparency and super-omniphobic properties in a simple,efficient way has become an urgent problem for people to overcome.In this paper,a method of fabricating omni-directional super-omniphobic glass surface with high transparency and large area based on maskless phase separation of polymer blends has been developed.Phase separation of polymer blends technology is a simple,efficient and low-cost maskless pattern forming method,and it can quickly realize large area pattern preparation on a variety of substrates such as glass,silicon wafer and PET.In addition,the nano-patterns obtained by this method have the characteristics of micro-disorder and macro-uniformity,so it can skillfully eliminate the iridescent effect caused by the ordered micro and nano structures.And according to the trapping effect,the fabrication of nanostructures with appropriate size will also have the effect of anti-reflection,so as to further broaden the application of super-omniphobic surfaces in the field of optics.On the other hand,both the omniphobic and optical properties of the surface are sensitive to the variations of the parameters of the structure fabricated on the surface.The phase separation of polymer blends method can realize the precise control of the nanostructure by simply adjusting the phase separation parameters.The phase separation system selected in this paper is polystyrene（PS）/polyphenylsilsesquioxane（PPSQ）system.The two-phase separation can be achieved by a simple spin coating method.Then,we can selectively remove the PS phase by O₂ reactive ion etching（RIE）and remain disordered PPSQ nano-pillars due to the high O₂plasma etching resistance of silicon element in PPSQ.In addition,by introducing a SU-8 bottom layer,disordered T-shape nanostructures composed of the top silicon-containing cap and the bottom SU-8 pillar were easily obtained by utilizing the difference in the resistance to O₂ etching between SU-8layer and silicon-containing polymers,without any other complex fabrication methods.And the T-shaped structure is very important for the acquisition of super-omniphobic properties.By exploring the effects of area fraction and height of nano-pillars on super-omniphobic and optical properties,we successfully facricated a large area（about 5x5cm）glass surface with super-omniphobic property and broad-spectrum transmission（visible waveband transmittance up to93.3%）.On the other hand,in order to further study the effect of the micro-nano structures on the super-omniphobic performance of the surface,in this paper,micron-scale and nano-scale silicon pores were fabricated by phase separation of polymer blends technology and other micro-nano manufacture technologies to explore the potential of their application on the super-omniphobic surface.In addition,the natural pitcher plant structure was successfully imitated on the nano-pore surface,which showed super-hydrophobicity（water contact angle 155°）,high oil repellency（oleic acid contact angle 142°）and excellent self-cleaning performance.