Design And Superhydrophobic Property Of Graphene-based Micro Wrinkle Structures

Superhydrophobic materials have been widely used in the fields of self-cleaning,water-oil separation,antibacterial,and fluid drag reduction since their excellent water-repellent properties.However,in a low temperature and high humidity environment,the superhydrophobic properties are lost because the condensation droplets are easy to nucleate on the surface and inside of microstructures,so it is still a big challenge to maintain the superhydrophobic properties in such environment.Therefore,it is vital to improving the stability of superhydrophobic performance by designing the microstructure of the material.At present,the traditional preparation process of superhydrophobic materials is complex,which is unfavorable to the flexible control of the structure and size of superhydrophobic materials.Therefore,it is urgent to develop a simple preparation process that can flexibly control the size of the microstructure of materials.In this paper,four kinds of graphene-based micro-nano hierarchical structures wrinkled films with microstructures of different sizes are designed.They are graphene-based ordered wrinkled film and disordered wrinkled film,graphene-based two-level gradient wrinkled film,and three-level gradient wrinkled film.Their superhydrophobic properties at room temperature and low temperature were investigated,and the maintenance mechanism of superhydrophobic stability was explained,Their anti-icing/deicing characteristics in a low-temperature environment and their stretch sensing characteristics in room temperature with water intrusion were investigated.To explore the influence of the micro-structure and its size on superhydrophobic properties,based on the reduced graphene oxide film obtained by suction filtration and reduction of graphene oxide,combined with the St?ber method to prepare three kinds of films.Finally,FDTS was used for surface modification to obtain superhydrophobic films with different structures.By characterizing the wettability and the dynamic behavior of water droplets impacting the surface,it is found that the micro-nano hierarchical structure films have better superhydrophobic properties at room temperature and low temperature.In addition,the superhydrophobic properties of micro-nano hierarchical structure films with different preparation parameters were studied.Firstly,the influence of pre-strain on the superhydrophobic properties was investigated.It was found that when the pre-strain was 400%,the contact angle and sliding angle of the film could reach161.4° and 1.2°,showing good superhydrophobic properties.The thickness of the film also influences the superhydrophobic properties of the material.When the pre-strain is controlled to 400%,the contact angle of the superhydrophobic material prepared by the concentration of GO is 0.2 mg/m L and the volume is 6 m L,even in the low-temperature condensation environment(-10℃,relative humidity 50±5%)is greater than 150° and the sliding angle is less than 3°.The superhydrophobic properties are well maintained in the low-temperature condensation environment.It is found that the pre-strain and the thickness of the film directly affect the microstructure size of the material,and the relationship between the microstructure size and the wettability is discussed in detail.Furthermore,the influence of differently structured microstructures on superhydrophobic properties was investigated.By adjusting the shrin kage order of the substrate tensile stress during the preparation process,the superhydrophobic films with ordered and disordered microstructures were prepared respectively.Through the characterization of wettability at room temperature and low temperature,it is found that both of them can maintain good superhydrophobic properties.The dynamic process of droplet impaction was characterized under low-temperature condensation(-10℃,relative humidity of 50±5%).It was found that droplets moved along the axis of impact on the ordered structure and could stay on the surface.However,droplets on the surface of the disordered structure deviated from the axis of symmetry and could bounce off the surface.The influence mechanism of the order of microstructure on the rebound direction of water droplets was also explored.In addition,owing to the excellent low-temperature superhydrophobic properties of the film,the excellent electro-thermal properties,and the temperature sensitivity of graphene materials,the film has the integrated function of superhydrophobic anti-icing properties,electro-thermal deicing properties,and sensing properties in the low-temperature condensation environment.Finally,the influence of gradient micro-wrinkle structures on superhydrophobic properties was studied.The second-order and three-step wrinkled films were prepared by the pre-stretching method,and the superhydrophobic films with gradient wettability distribution were obtained by PDMS surface treatment.It is found that even at 300% or 400% tensile strain,the contact angle of the film is still greater than 150°,and there is still an air layer between the water and the film.The film has also been explored in the presence of water droplets,and it has been found that water droplets bouncing off the stretched film automatically bounce off the surface.In addition,due to the particularity of the film structures and the good electrical conductivity of graphene material,it has high-performance tensile sensing properties.And the stretch-sensing film can be applied to rainy days,underwater,acid,and alkali droplet corrosion environments,expanding its application scope.