Oxygen inhibition induced hydrophilic-hydrophobic surface for self-assembled droplet microarrays
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Oxygen inhibition induced hydrophilic‑hydrophobic surface for self‑assembled droplet microarrays Peng Chen1 · Mujun Li1 · Jinfeng Qiu1 · Tao Zhang1 · Yuxuan Sun1 Received: 23 July 2019 / Accepted: 20 July 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract 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 μ 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 selfassembled 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. Keywords Self-assembled droplet microarrays · Maskless lithography · Hydrophilichydrophobic patterned surface · Oxygen inhibition
1 Introduction The hydrophilic-hydrophobic patterned surface is significant for the study of the wettability behavior of liquids, and has been studied extensively recently for its applications in self-propelled motion of droplets[1], dropwise condensation[2] and self-assembled droplet microarrays[3]. Due to the significant difference in wettability on surface, liquid droplet spontaneously flows from the hydrophobic region to the hydrophilic region under the effect of the difference in tension[4]. Nevertheless, how to effectively achieve hydrophilic-hydrophobic surface with controllable wettability remains a very concerned issue, which usually involves a series of complex surface treatment and patterned processes[5–7] . * Mujun Li [email protected] 1
Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei 230026, People’s Republic of China
So far, a variety of approaches have been developed to generate the hydrophilic-hydrophobic surface. By depositing a hydrophobic material (fluorinated ethylene propylene) onto the glass surface and then drilling a bare glass ring on the surface, a discontinuous wettability surface can be created to successfully achieve water collection[8].
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