飞秒激光诱导钛表面可控微纳结构用于水下气泡操纵

Controllable micro-/nanostructures on titanium surface induced by femtosecond laser for underwater air bubble manipulation

针对典型金属材料钛,利用自主搭建的飞秒激光振镜扫描加工系统,加工了具有特定形貌特征的多尺度微纳结构.在此基础上对多尺度微纳结构的可逆润湿性及水下气泡操纵特性进行了实验探究,并从微观界面化学的角度阐释了可逆润湿性的调谐机理.研究结果表明:在飞秒激光烧蚀挤压作用下,钛表面诱导的多尺度微纳结构对原始表面的润湿性具有放大效应,固液接触角减小,水下气泡接触角增大;在辅助加热条件下,固液接触角增大,水下气泡接触角同时减小,气泡在表面完全铺展;随后将超疏水表面置于紫外灯下曝光,多尺度微纳结构上的液体接触角又开始减小,并最终实现了超疏水到超亲水性以及水下超亲气到超疏气的可逆调谐.另外,液体接触角与水下气泡接触角的可逆调谐特性呈现相反的变化趋势,这与固液气三相接触线的移动机制密切相关.本文对实现钛表面微纳结构设计与调控,提高具有可逆润湿性的金属表面在水下气泡操纵与收集,以及污水处理等领域的应用都具有重要意义.

Bubbles exist widely in nature and industrial process.The research on bubbles has attracted the attention of many scientists due to the importance of practical application and a large number of studies on bubbles have been carried out since last century.In some cases,the gas in water is often in the form of bubbles,and these bubbles will have some adverse effects on the surface wettability.However,the presence of underwater bubbles also has beneficial effects on natural organisms and human beings.Therefore,it is necessary to study the surface construction of superaerophobicity or superaerophilicity and the manipulation of bubbles.A series of multiscale metallic micro-/nanostructures have been fabricated on typical titanium surface with different morphological features by using self-developed femtosecond laser scanning processing system,which can be controlled through parameters such as laser power,scanning time and scanning intervals.On this basis,the reversible wetting characteristics of multiscale micro-/nanostructures and underwater air bubble manipulation were experimentally investigated by using strategies such as ultraviolet light exposure and heating.The tuning mechanism of reversible wettability was clarified from the perspective of interface chemistry.The research results show that:the original titanium surface wettability has been amplified by multiscale micro-/nanostructures induced by femtosecond laser ablation and solid-liquid contact angle changed to 1°from 48°,being superhydrophilic and bubble contact angle changed to 156°from 136°,being superaerophobic,with bubble sliding angle only being 2°and an extremely low bubble adhesion force.However,under the condition of auxiliary heating,solid-liquid contact angle increased gradually to be superhydrophobic,with liquid sliding angle only being 8°,the surface adhesion force dropping sharply and underwater bubble contact angle rising gradually.The liquid contact angle on the multiscale micro-/nanostructures gradually decreased after the exposure of superhydrophobic surface under the ultraviolet lamp and finally the reversible tuning of superhydrophobic to superhydrophilic could be realized.Furthermore,there is a trend that the reversible tuning characteristics of the liquid contact angle and the bubble contact angle show the opposite way,which is closely related to the moving mechanism of the solid-liquid-gas contact line.The surface micro-/nanostructures with tunable bubble affinity and wettability are prepared by combining the femtosecond laser micromachining technology and the cutting-edge bubble manipulation technology.At the same time,the chemical mechanism of the underwater affinity and wettability of the bubble is studied.The theoretical model of the wettability of the bubble is established and the potential application of the bubble collection is explored so as to solve the problem of the manipulation of the bubble in the aqueous medium.Through our research,the inspirations will be found for the operation of bubbles in industrial production and daily life,which is of great value for dealing with a series of problems caused by bubbles and driving the generation of new bubble manipulation topics.The research results of this paper are also of great significance to the design and fabrication of micro-/nanostructures on typical metal surface and improving the application of metallic surface with reversible wetting characteristics in the fields of underwater bubble manipulation and collection and sewage treatment.