Fabrication Of Superhydrophobic Surfaces By Femtosecond Laser And Its Application

After billions of years of evolution,animals and plants in nature have developed a variety of unique functions.With the development of science and technology,people have begun to use various advanced microscope to study the superhydrophobic surface,starting from understanding nature to imitating nature.Furthermore,the bionic structure,bionic material and bionic function are researched.Femtosecond laser as a newly developed micro-nano processing method in recent decades,due to its high machining accuracy,wide material processing range,and low thermal effect during machining,has been gradually applied to various precision machining fields.Normally,researchers use femtosecond lasers to fabricate micro-nano structures on the surface of materials,and then use the chemical coating to achieve superhydrophobic.However,with the development of research,a series of research and application problems have also arisen: whether the metal surface can achieve superhydrophobicity without using chemical coatings,and how about the performance of this superhydrophobic metal surface.In addition,whether the superhydrophobic surface can be quickly made by femtosecond laser.Whether the superhydrophobic surface can be applied to rainwater harvesting.And for viscous food,whether the surface can be used to achieve a superhydrophobic anti-stick surface that meets food safety requirements,etc.This research is based on femtosecond laser fabrication combined with the heat treatment,by using the uncoated superhydrophobic metal surface,and studied its various properties including self-cleaning,corrosion resistance,and liquid repellency,etc.Then combined with heat imprinting method to prepare the superhydrophobic plastic surface,and build a rain collection device with high collection efficiency.Finally,the superhydrophobic metal surfaces have been fabricated by using femtosecond laser and bee wax,which does not stick to viscous liquids such as yogurt,tomato ketchup and honey.This superhydrophobic surface provides a certain basis for the application of food processing.The main contents are as follows:1.By using the femtosecond laser to fabricate micro-nano structures on the surface of common metals(aluminum,titanium,zinc,aluminum alloy,copper,copper-titanium alloy,iron and stainless steel),then using the heat treatment at 200 °C for 30 minutes to makes the metal surface after laser ablation rapidly transform from the superhydrophilic state to the superhydrophobic state.The superhydrophobic surface can be achieved quickly without coating.At the same time,the transformation of the metal surface from superhydrophilic to superhydrophobic state is explained by EDS,FTIR and other characterizations.By testing the superhydrophobic surface fabricated by laser ablation combined with heat treatment,it is found that the superhydrophobic metal surface has good stability such as corrosion resistance,liquid repellency,and selfhealing properties.2.By using the femtosecond laser to fabricate micro-nano groove-like structure on the surface of aluminum alloy,then the template and sample surface before and after imprinting were characterized.The micro-nano structure on the surface of the aluminum alloy can be imprinted to the surface of the hydrophobic plastic,so that the plastic surface can have superhydrophobic properties after imprinting.This method can significantly improve the processing speed of superhydrophobic surfaces,and can realize the fabrication of large-area superhydrophobic surfaces.The plastic surface can still have superhydrophobic properties after being imprinted by the aluminum alloy which had been used more than 50 times.This method can reduce the cost while increasing the processing speed.3.Building an artificial precipitation simulation system,to test the funnel-shaped rain collection devices with superhydrophobic plastic surfaces combined with different inclination angles.By changing the inclination angle,the rain collection efficiency of the superhydrophobic funnel-shaped rain collection devices at different angles was measured,and compared with the funnel-shaped rainwater collection device with different inclination angles composed of untreated plastic.The measurement results show that for the light rain that is difficult to collect,the efficiency of the rainwater collection device composed of superhydrophobic plastic surface is significantly improved compared with the unprocessed surface;the rainwater collection device composed of the superhydrophobic plastic surface can be up to 90%.The high rainwater collection efficiency realizes the efficient collection of light rain.4.By using the femtosecond laser to process the micro-nano structure on the stainless steel surface,and then by combining the food-safe hydrophobic coating,the super-hydrophobic metal surface with non-stick yogurt,honey and other viscous liquids is processed.It can effectively reduce the residual problem of viscous liquids such as yogurt and honey in the process of processing or stirring,which is safe and reliable.It provides the possibility for the application of superhydrophobic surfaces in the field of food processing.