Behavioral Characteristics And Interfacial Properties Of Lubricant At The Interface Of Multi-level Structured Materials

With the continuous exploration and development in the oceans and polar regions,the demand for multi-functional materials such as self-cleaning,fluid drag reduction,anti-icing,anti-fouling,is increasingly strong,and becomes an urgent problem to be solved.Slippery liquid-infused porous surfaces(SLIPS),inspired by the biological multifunctional surfaces of Nepenthes,dolphins,etc.which constructed by secreting mucus on the structured surface,show great research and development value.These current SLIPS are,however,still hampered by problems:the short residence time of lubricant at the contact interface can easily lead to the problem of performance failure.SLIPS are typically composed of structured substrate and lubricant.The storage and stabilization of lubricant at the material interface involves many interface sciences.Therefore,grasping the behavior characteristics and interface action mechanism of lubricant at the multi-level structure materials interface is a prerequisite for breaking through the current research bottleneck.Based on the above requirements,this work carries out research on the behavioral characteristics and interface properties of lubricant on the interface of multi-level structured materials.Starting from exploring the influence of different materials characteristics on the behavior and interface characteristics of lubricant,the design principles and construction methods of stable SLIPS are proposed,and several SLIPS with high lubricant layer stability are designed,prepared and developed.The research results provide theoretical guidance and technical support for the development of SLIPS with stable and durable performance.A series of SLIPS with different structural characteristic parameters Ra were constructed by PDMS replication.The influence of the structural characteristics of substrate and the interface compatibility between substrate and lubricant on the stability of lubricant layer was studied.It is found that the amount of lubricant on the substrate surface is mainly controlled by Ra,and its capacity to store lubricant and the average lubricant layer thickness increase as Ra increases.The concept of structural lubricity factor L_S is proposed,and it is verified that the interface properties such as anti-algae adhesion and anti-icing on SLIPS become more excellent as the structural lubricity factor increases.The study of interface compatibility on the stability of lubricant ayer shows that improving the chemical compatibility between interfaces can significantly improve the stability of lubricant at interface,but may cause the lubricant to swell in the substrate.Considering that anisotropy is one of the important features of the surface structure,The SLIPS with anisotropic microstructure was successfully prepared by using the strategy of magnetic field assisted anisotropic construction,sacrificial template method and PDMS replica molding.The influence of anisotropic structure characteristics on the behavior and interface properties of lubricant at the interface of SLIPS was also studied.It is found that the anisotropic microstructure affect the wettability,algea adhesion behavior,ice adhesion strength,etc.of the SLIPS.In terms of wettability,the contact angle(CA)and silding angle(SA)in the vertical direction are larger than those in the parallel direction.In terms of algea adhesion behavior,the distribution of algea on the anisotropic SLIPS shows anisotropy.In terms of ice adhesion strength,the force required to peel ice from a direction perpendicular to the anisotropic stripe structure is greater than the force required to peel ice from a parallel direction.Based on the influence of structural parameters on the behavior characteristics of lubricant,from the perspective of improving the structural lubricity factor L_S,modified copper powder and tape were used to preparat sacrificial template,and SLIPS with nested hole structure(LIHSPS)was constructed by PDMS replica molding.The hierarchical structure of substract greatly improves the surface structure lubricity factor,and increases the storage capacity and stability of the surface lubricant.Compared with the SLIPS with a single layer of pore structure,LIHSPS has more excellent anti-algea adhesion ability,self-cleaning ability and anti-icing ability,and the amount of algea adhesion and icing adhesion strength on the surface decreases by nearly 50%and 40%,respectively.A layered 3D fibrous porous structured SLIPS(LIFPS)was designed to further improve the stability and self-healing rate of the lubricant layer,and the designed structure was achieved through a novel strategy of using modified water-soluble non-woven fabric as sacrificial template.The internal structure of LIFPS contains many ordered large cavities for storing lubricant,similar to the nectaries of pitcher plants,thereby increasing the storage capacity of lubricant.The average of lubricat layer thickness can reach 50?m.The fibrous pore structure connected between the cavities and between the inside and the outside provides channels for the circulation of lubricant in various areas,resulting in a greatly improved self-replenishing rate,which reaches a replenish rate of nearly 90%in 10 s.This rapid self-replenishing ability can be used to prevent performance degradation after the loss of lubricant.To improve the flexibility of SLIPS in practical applications,a reconfigurable structural design strategy was used to prepare a slippery paraffin-based organogel coating(SOS)with completely repairable surface properties and internal structure.Due to the excellent interfacial compatibility between paraffin and silicone oil,the organogel has a strong ability to maintain the lubricant layer.Under the test condition of 6000 rpm,the lubricant retention rate is still close to 60%.This organogel possess two forms of repair.The self-healing of lubricantl ayer comes from the fluidity and self-supplementation of the silicone oil in network skeleton,and the heat-assisted repairing comes from the renewable ability of paraffin skeleton,which can effectively repair the internal structure.The coating can be flexibly applied to various common substrate and form an effective protective layer,which greatly improve its flexibility in practical applications.