Oxygen inhibition induced hydrophilic-hydrophobic surface for self-assembled droplet microarrays

Hydrophilic-hydrophobic surface is vital for the study of the wettability behavior of microdroplets. In this paper, a method for preparation of hydrophilic-hydrophobic patterned surface is proposed based on the oxygen inhibition effect. Oxygen inhibition is very common in photo-cured process, and usually should be avoided for its adverse effect on curing quality. However, it also results in numerous nanostructures naturally formed on the cured layer surface, and the density and sizes of the nanostructures can be modulated conveniently by adjusting the exposure time. Based on this phenomenon, the cured layer surface having hydrophobicity can be processed. The contact angle system is used to measure the contact angle of the cured layer surface, and the morphology of the cured layer surface is measured in detail by atomic force microscopy and scanning electron microscope.The hydrophobic layer is only 1.5 $$\upmu $$ m thick. By combining maskless lithography, patterned surface with nanostructures can be easily formed in just one step without any special treatment. This helps us to generate highly controllable hydrophilic-hydrophobic surface effectively in a very simple and low-cost way. With this method self-assembled droplet microarrays are successfully achieved. The results offer a new idea for the control of surface wettability and may find wide potential applications in microfluidics.