【作者】 吕春华；

【导师】 殷学锋；

【作者基本信息】 浙江大学 ， 分析化学， 2007， 博士

【摘要】 微流控学(Microfluidics)是在微米级结构中操控纳升至皮升体积流体的技术与科学,是近十年来迅速崛起的新交叉学科。流体在微流控芯片微米级通道中,由于尺度效应导致了许多不同于宏观体系的特点,促进了分析化学的发展。但是,当前微流控器件的加工技术还难以满足微流控学快速发展的需要,例如玻璃微流控芯片封接难度大,集成度低;用于复制聚合物芯片的阳模加工工艺复杂;高深宽比和三维微结构的制作方法尚稀见报道等。为促进了微流控学的进一步发展,本文研究了以SU-8负光胶制作和封接微流控器件的新技术。第一章综述了制作微流控芯片和SU-8负光胶加工技术的现状。第二章提出了一种用简便快速封合玻璃微流控芯片的新方法。利用毛细作用将熔化的液体硫填充开放的玻璃微通道,冷却后的固体硫形成牺牲层材料。用紫外光固化的SU-8光刻胶作为粘接剂,同时利用通道内黄色的硫牺牲层阻挡紫外光对通道与盖片结合处SU-8粘接剂的曝光,封接后得到的微通道表面性质基本一致。此方法可以简单快速的实现玻璃芯片的低温封接,有效提高了大面积玻璃芯片的封接成功率;而且有利于在玻璃芯片内集成金属电极等热敏感材料。制得的玻璃芯片已成功用于氨基酸的电泳分离。第三章研究了一种制作高聚物微流控芯片镍阳模的新工艺。采用抛光的镍片作为电铸基底,在光刻后的SU-8微结构中,以镍基片作为阳极,通过16～30 A/dm~2的电流密度阳极电解刻蚀5 min,清除SU-8微通道底部镍片表面的氧化物,并刻蚀得到10～20μm深的凹坑。用此SU-8微结构作为电铸模板,以镍基片作为阴极,用1～2 A/dm~2电流密度电铸5 h,制得了微结构倾角为83°深宽比较大的镍阳模。凹坑的设计,有效提高了电沉积的镍结构和基底镍片间结合力,在普通化学实验室中制得了长寿命的具有正拔模斜度镍阳模。用热压法制得PMMA聚合物芯片,并成功用于DNA片段的分离。第四章提出了利用ITO玻璃的导电性和透光性,在ITO导电层上电沉积镍金属薄膜制作光刻掩模和电铸金属的种子层,加工高深宽比金属微结构的简易方法。在导电玻璃的ITO层上涂覆薄层AZ4620正光胶,用常规的接触式曝光法UV光刻显影后,将光刻掩模上的图形转移到AZ4620光胶层上。利用ITO玻璃的导电性,在光刻胶曝光处电沉积镍,使掩模图形转移到ITO玻璃表面的镍薄膜上。在镍掩模上涂覆SU-8厚胶层,使UV光透过ITO玻璃基底对SU-8光胶层进行背面曝光,制得高深宽比SU-8微结构。最后以SU-8微结构作为模板,以ITO表面的镍掩模作为种子层,通过电铸得到深宽比高达15、侧壁垂直度为89°的金属微结构。此方法使用设备简单,加工成本低,在普通实验室实现了高深宽比的金属微结构的简易加工。第五章提出了将相变化牺牲层材料硫,用于封接SU-8敞开通道,制作SU-8的微流控芯片;而且在封接的SU-8层上通过光刻制作微结构,用叠层法制备了多层三维SU-8微流控芯片。SU-8光刻胶中的有机溶剂与硫之间不存在相互反应及溶解问题,加热后只要在微通道末端施加负压就可以将通道内的液体硫抽出,与现有的牺牲层的方法相比较,大大缩短了牺牲层的去除时间。实验成功制得了各种形状和尺寸的SU-8微通道和叠层三维结构。制得的三维SU-8微流控芯片在芯片毛细管电泳分离、有机合成微反应以及实现芯片的多功能集成化等方面可望有广泛的应用前景。更多还原

【Abstract】 Microfluidics is the science and technology of systems that process or manipulate small(10^-9to 10^-18litres)amounts of fluids,using channels with dimensions of tens to hundreds of micrometres.Compared to macroscale laboratory techniques,microfluidic chip has a number of advantages over conventional chemical processes,which is expected to promote the development of analytical instrumentation to minimization,integration and automation.However,the present microfabrication technology can not follow the rapid development of microfluidics.For example,it is difficult to seal electrodes within glass microchip and tedious to fabricate molds used for replication of plastic chips. The fabrication of high-respect-ratio and 3-dimensional micro structure without using special instrtmaents is still on development.In this dissertation,several new fabrication and sealing techniques using SU-8 negative photoresist are studied and reported as following:In chapter 1,the current status in the field of fabricating microfluidic chip and the fabrication process for SU-8 microstructure was reviewed.In chapter 2,a novel method for adhesive bonding of glass microfluidic chips at room temperature was developed.Channels in an etched glass substrate were filled with a heated sulfur liquid at 120℃that formed a solid sacrificial layer cooled to 95℃.Then,the etched substrate and cover substrate were bonded together utilizing a SU-8 adhesive layer.To avoid any chance ofphotoresist curing inside the channel,the UV light was exposed through sulfur sacrificial layer.Once the sealing step was complete,the sacrificial layer was melted and removed,leaving enclosed microfluidic channels.The chips have been used successfully for the separation of amino acids. Another advantage of this method is the possibility of integration of metal electrodes into a microfluidic glass device.In chapter 3,a simple and inexpensive method to fabricate nickel mold insert for replicating of plastic microfluidic chips was developed.A polished nickel plate was used as a substrate on which a thick SU-8 photoresist layer was coated.Conventional contact UV lithography was applied to pattern the thick SU-8 photoresist layer.After development,electroetching was conducted at a large current density of 16～30 A/dm² for 5 min to clean the nickel surface in the SU-8 recesses where unexposed SU-8 had been lifted up and to form 5～10μm deep root structures for increasing the strength of the nickel insert electroformed later on.By using the fabricated SU-8 microstructure as a template and nickel substrate as an electrode supplying current,nickel mold insert with a sidewall slope of 83°and high aspect ratio were successfully fabricated within 5 h in a conventional chemical laboratory.More than 500 PMMA microfluidic chips were replicated by hot-embossing.The chips have been used successfully for the separation of DNA fragments.In chapter 4,a simple and low cost method to fabricate high aspect ratio metallic microstructures without the requirement of specialized equipments was described. Conventional contact UV lithography was applied to pattern a thin AZ 4620 positive photoresist film coated on the ITO layer of the glass substrate.After development of the photoresist,a nickel film was electrodeposited in the recesses where exposed AZ 4620 had been lifted up.The formed Ni pattern was then functioned as an exposure mask to pattern a thick SU-8 photoresist coated on it.SU-8 microstructures with high aspect ratio were fabricated with reverse-side exposure.By using the fabricated SU-8 microstructure as a template and the nickel pattern on the ITO glass substrate as the seed layer,nickel microstructures with high aspect ratio of about 15 and a sidewall slope of 89°were successfully fabricated in conventional chemical laboratory.In chapter 5,micro fabrication of embedded channels in SU-8 microchip using phase changing sacrificial material sulfur was developed,in which SU-8 open channels were sealed by another coating layer of SU-8 after being filled with liquified sulfur at 120℃and solidified at 95℃to form a sacrificial layer.Based on this new technique,3-dimensional SU-8 microchip was fabricated for first time by photolithography to pattern the top SU-8 photoresist layer sealed on the microchannels.By repeating the above steps,multi-layered structures could be fabricated.Unlike conventional sacrificial layer techniques,this method drastically simplifies and shortens the sacrificial layer removal process,especially for long and complex channel networks.The fabrication process is very flexible and opens new possibilities to construct complex 3-D structures in SU-8,which has very promising applications in electrophoresis microchips,micro-mixers and organic synthesis reactions carried out in microfluidics reactors.更多还原