Preparation And Application Of Magnetically Responsive Superhydrophobic Surface Based On Electrostatic Air Spray Deposition

Recently,superhydrophobic surfaces with switchable liquid-solid adhesion have been uniquely used in droplet-based microfluidics,droplet manipulation,and anti-icing.The construction of adjustable microstructures is an effective method to obtain such controllable adhesion surface.However,construction of patterned microstructures relies on moulds or requires special chemical treatments so that involves complex preparation process in most methods.To solve this problem,this paper proposes a new method for preparing magnetically responsive superhydrophobic surface based on electrostatic air spray deposition(EASD).the EASD theory was analyzed,and the preparation experiment was explored.The main research contents include the following four aspects:(1)The basic theory of superhydrophobicity and EASD were analyzed and studied.The wettability,surface tension,surface free energy,contact angle,contact hysteresis and sliding angle were introduced.The contact angle and sliding angle were selected to represent the hydrophobicity of the surface according to the actual experiment.The atomization process of the liquid flow in the EASD,the auxiliary function of the static electricity and the movement force analysis of the atomized droplet were analyzed.(2)The magnetically responsive superhydrophobic surface was prepared by experiments and the influence of different preparation parameters on the surface morphology and hydrophobicity were investigated.The formation mechanism of was introduced.The surface was composed of dense black micropillars.Compared with the air spray method,the advantages of the EASD were theoretically analyzed,including better uniformity,solution utilization and environmental friendliness.The experimental equipment was designed and built,and the relevant experimental materials and testing instruments were selected.The preparation process of the sample surface was introduced in detail and the surface was characterized.The influence of various parameters(such as electrostatic voltage,air pressure,magnetic field)on the samples morphology and properties were studied.(3)The characteristics of magnetically responsive superhydrophobic surface and its application in droplet transportation were verified.The prepared surface can be reversibly transformed between the high-adhesion state and the low-adhesion state by on/off switching of an external magnetic field.After 2.2 k Pa pressure load was applied,the surface contact angle was 144° with an applied magnetic field of 0.4 T.After heated at 90? for more than 90 minutes,the surface can almost obtain superhydrophobicity in the absence of a magnetic field.It was verified that water droplets transportation with different volume and quantity can be realized by using the switchable adhesion.(4)The hydrophobicity,adhesion and application in droplet manipulation were tested.The surface composed of micro-and nanostructures was prepared by simply spraying carbon nanoparticles on the prepared magnetically responsive superhydrophobic surface.The hydrophobicity and adhesion of the surface prepared by different time of carbon spraying were compared.It was verified that the micronano composite structure was beneficial to reduce the surface adhesion and enhance the hydrophobicity.The multiscale structures surface realized the active and reversible water droplets driven and the control of water droplets movement direction and target position.