Fabrication Of Gradient/Patterned Oil Wettability Surfaces On Aluminum Substrates

Wettability, as one of the important properties on solid surface, depends on both surface microstructures and chemical composition. The achievement of wettability control shows great potential for application in various industries. Gradient and patterned wettability surfaces, as two typical aspects of wettability control, have great significance in many fields including microfluidics, bioscience and pharmaceutical industry.To date, many methods have been tried to fabricate gradient and patterned wettability surfaces, however, most of the methods tend to be complicated, at a high cost, invalid to oil or confined to limited types of materials. Based on the above problems, a simple and economical method with high efficient—Atmospheric Pressure Cold Plasma Jets (APPJ), has been proposed to obtain gradient and patterned oil wettability surface based on Al substrate.By exploring on the generation, characteristics diagnosis, parameter control of APPJ, the APPJ suitable for regulating of metal surface wettability has been obtained. The analysis of reaction mechanism between APPJ and superoleophobic surfaces was carried out by characterizing surface micro morphologies using scanning electron microscopy (SEM) and chemical composition using fourier transform infrared spectrophotometry (FTIR) and energy-dispersive spectroscopy (EDS). It shows that the wettability alteration is due to the decrease of lyophobic groups and increase of the lyophili groups, and this transform of functional groups is attributed to the active substance contained in APPJ.Through adjusting the processing parameters of APPJ, gradient oil wettability surfaces based on Al substrates were prepared by nozzle movement and changes of treatment time and section. The analysis of influence of processing time to the wettabitity shows that during the processing, the lyophobicity of surfaces weakens gradually and finally shows superlyophilicity. In addition, the wettable state of liquid drops on the obtained surfaces were observed.By using APPJ coupled with masks, various superlyophilicity-superlyophobic patterns were obtained, making a surface appear extremely high wettability contrast. And the movement of liquid droplet in the fabricated superoleophilic channel was studied. It indicates that the superoleophilic channel on superoleophobic Al surfaces has property of transporting liquid droplets directionally.