【作者】 王磊；

【导师】 韩晓军；

【作者基本信息】 哈尔滨工业大学 ， 化学工程与技术， 2015， 博士

【摘要】 流体是物质的重要存在形式,微混合和微流控技术是在微米尺度空间里对流体进行混合和操控的研究。与普通大量溶液的反应相比,微混合和微流控技术具有其独特而又明显的优势。但是,在如此狭小的微通道内、雷诺系数非常小的情况下,如何实现对微液滴的操控、如何提高微通道内的混合效率和如何将微混合技术应用于复合纳米材料的自组装领域成为科学家们的研究重点。因此,本论文针对这些问题开展了详细的研究。利用有限空间等离子体氧化自组装膜的方法,以简单易购的载玻片和盖玻片为载体,利用材料表面亲疏水性成分的浓度差可以驱动微液滴运动的原理,实现了在敞开的具有化学成分梯度表面的微芯片上对微液滴流动的控制研究。该方法能够良好的控制所制备的化学成分梯度表面的深度和长度等性质。通过计算,可以得到,本实验中微液滴移动的最大速度是0.64 mm/s,对应的化学梯度表面的接触角为70°。该方法操作简便灵活,使用材料价廉易购,重现性非常好,在生物分析领域有广泛的应用前景。基于微通道内的单乳液方法,以含有碳酸氢铵、纳米金棒和海藻酸钠的水溶液为分散相,以含有钙离子的十一醇溶液为连续相,成功制备出大小可控的具有海藻酸钙聚合物外壳的水相微液滴(300~1000μm),即微反应器。该微反应器的海藻酸钙聚合物外壁厚度可以利用钙离子偶联剂的浓度和反应时间来良好地控制。在此基础上,鉴于纳米金棒的光热效应,以波长为808 nm的激光为光源,引发碳酸氢铵的分解反应产生二氧化碳气体,从而制备出海藻酸钙聚合物包裹的二氧化碳气体微胶囊。鉴于气体微胶囊的感压性,成功制备了一个压力传感器,检测范围为0.1~0.55 KPa。利用提高流体之间接触面积和引起通道中局部对流的方法,利用COMSOL软件进行模拟计算并优化结构设计,以光刻法为基础,以PDMS为原料,成功地设计和制备出三种具有不同结构的被动微混合器,包括具有对称半圆柱沟槽结构、非对称半圆柱沟槽结构和三角形障碍物阵列的被动微混合器。实验和模拟的结果都证实了这些微混合器在较大的雷诺系数范围内对不同黏度的流体的混合效果具有增强作用。对于具有对称沟槽结构和非对称沟槽结构的两种微混合器,流体间混合效果的增强可以在19 mm内完成;对于具有三角形障碍物阵列的微混合器,混合距离被缩短至6.4 mm。当Re等于0.1时,混合效率高达91.4%,是普通Y-通道混合效率的2.02倍。在Re等于10的情况下,具有对称半圆柱沟槽、非对称半圆柱沟槽、三角形障碍物阵列的三类被动微混合器对酚酞水溶液的混合效率分别是普通Y-形微通道的混合效率的2.22倍、3.87倍和2.67倍。以上设计结构简单、混合距离短、混合效率高,在生物分析检测领域具有广泛的应用前景。基于对微混合现象和过程的理解,以硝酸银为氧化剂,以邻苯二胺为还原剂,通过调整两种流体进入微通道的流速和扩散速度,引发硝酸银和邻苯二胺之间的氧化还原反应,从而诱导了反应的初级产物(银纳米粒子和邻苯二胺二聚体)的进一步自组装,发现了一种简单高效无模板的制备多种形貌的银粒子修饰的聚邻苯二胺组装体的方法。通过利用COMSOL软件进行模拟,分析了产生多种形貌的银粒子修饰的聚邻苯二胺组装体的可能机理。基于银粒子修饰的聚邻苯二胺微球组装体对过氧化氢具有良好的催化作用,成功制备出一个过氧化氢传感器,其检测范围是20~180μM,检出限是5.7μM。利用微混合技术,以溶解有两亲性聚合物修饰的多种贵金属纳米粒子为组装单元的THF溶液为中间相,以纯水为扩散相,通过调整两相之间的扩散速度,实现了制备多种形貌的贵金属纳米粒子自组装体的研究。文中详细研究了纳米金棒的长径比、聚合物的分子量以及两种流体的流速和扩散速度对自组装体形貌的影响。基于此,成功制备出一种具有载药功能的阴阳结构微米马达。该结构的粒径范围在0.5~4μm之间,马达的运动速率范围是5~120μm/s;利用纳米金棒的光热效应,该载药马达能够在70~80 min内实现药物的全部释放。该研究为未来微流控体系内的纳米材料自组装和微纳马达在生物领域中的应用奠定了基础。更多还原

【Abstract】 The past decade has witnessed the considerable development of microfluidic and micromixing technology, which have been developed as a powerful platform for many different applications, such as biomedical diagnostics, engineering of tissues, drug development and chemical synthesis or assembly. Because there are several obvious advantages of microfluidics that have been proved over conventional bulk reaction. However, there is a specific small Reynolds number of the liquid flows in such microchannels, where turbulent mixing does not take place. Consequently, it is really significant for scientists to carry out experiments, in order to know the mechanism of droplet movtion, the way to enhance mixing effect under such small Re, and how to utilize mixing technique in the area of chemical systhesis and assembly. In this thesis, researches were conducted to solve some of the above problems.In order to understand the properties and movement of liquid, especially, single droplets, the control of their movement was realized using a chemical gradient surface fabricated within limited space for plasma oxidation. In this method, the properites of the chemical gradient surface can be easily tuned by changing the height, width and length of the wedge space. The direction controlled motion of single droplet was realized on this chemical gradient surface. The droplet moved towards the surface with smaller contact angle. In this work, the maximum velocity of the droplet is 0.64 mm/s, where the contact angle is 70°. This method is robust, simple, reproducible and cheap, which has a great potential in the application in biological area.Based on the understanding of the properties of a single droplet, the generation of droplets was transferred into a micro chip, where water droplets(300~1000 μm) formed continuously with good control over their size and thickness by tuning the concentration of the cross linker and reaction time. Based on the obtained droplets, a microreactor for gas capsule was fabricated using gold nanorods and ammonium bicarbonate. Due to the property of the gold nanorods of absorbing laser and giving off heat, a decomposition reaction of ammonium bicarbonate based on the heat was realized in the microdroplets. Carbon dioxide would be generated in this reaction and try to leave the main liquid droplet, thus leading to the formation of gas capsules due to the polymer on the surface of the main droplet. Functionality of the gas capsules was also realized by introducing magnetic or fluroscence nanoparticles while preparation. Addtionlly, since the gas capsules were sensitive to pressure, a pressure sensor with the detection range from 0.1 to 0.55 KPa was fabricated for the detection of localized pressure.Different passive micromixers were designed, optimized and fabricated to enhance the mixing efficiency in microdevices, including mixers with symmetrical/ asymmetrical cylindrical grooves and the array of triangle baffles. All the experimental and simulated results proved the enhancement of the mixing effect in a wide range of Re number. For the micromixers with symmetrical/asymmetrical cylindrical grooves, the mixing performance can be improved within 19 mm. While the mixing performance can be enhanced within 6.4 mm for the mixer with the array of triangle baffles. When Re is 0.1, the mixing efficiency is as high as 91.4% in the mixer with the array of triangle baffles, which is 2.02-time better than that of the common Y-mixer. When Re is 10, the mixing performance of mixers with symmetrical/ asymmetrical cylindrical grooves and the array of triangle baffles is 2.22-time, 3.87-time and 2.67-time better than that of the common Y-mixer.Based on the well understanding of miscible solutions, chemical reaction and self-assembly of products can also occur when different reactents mix with each other. The redox reaction between Ag NO3 and OPD occured while the mixing of the two solutions, where Ag NPs-modified-Po PD with different morphologies were obtained by tuning mixing conditions, such as shearing force. COMSOL software was utilized for the analysis of the possible mechanism of the mixing process as well. Furthermore, a sensor for hydrogen dioxide, with a detection range from 20 to 180 μM, was fabricated based on the Ag NPs-modified-Po PD nanospheres.Self-assembly of different building blocks based on different noble metal nanoparticles was then conducted in the microchannel, where assemblies with different morphologies or properties can be obtained with the diffusion of different flows. The investigation of different effect was also conducted, including the aspect ratio of Au NRs, polymer weight and mixing distance. Based on that, a Janus structure(0.5~4 μm) was obtained by introducing free polymer into the system, which can be utilized for the fabrication of micromotor for the transfer an d controlled release of loaded drugs. The micromotor had a tunable velocity ranging from 5 to 120 μm/s, with the change of the concentration of hydrogen peroxide. Laser was the switch for the controlled release of loaded drug. The total release will cost about 70~80 min.更多还原