【作者】 吕宏峰；

【导师】 闫卫平；

【作者基本信息】 大连理工大学 ， 微电子学与固体电子学， 2013， 博士

【摘要】 微流控电泳芯片是微全分析系统的重要组成部分,它以高效、快速、样品消耗少等优点,在DNA测序、氨基酸分离、药物筛选等方面得到了广泛的应用,已经成为当前生物科学和化学分析领域的重要研究平台。但是,传统微流控电泳芯片需要几百伏甚至数千伏的电压完成样品的进样和分离,不仅存在安全隐患,而且通常高压电源体积较大,不利于系统的微型化和集成化。针对上述问题,有学者提出低电压电泳芯片的设想,但目前它还处于初级研究阶段,需要完成以下关键技术才能使芯片系统得到更好的应用。包括解决阵列电极直接与样品溶液接触产生气泡影响样品迁移问题,芯片结构的优化设计,芯片制作的最佳工艺,芯片简易低成本的亲水改性方法,小型化控制系统与检测系统的研制等。为此,本文针对低电压电泳芯片系统的关键技术开展研究。低电压电泳芯片和传统电泳芯片的工作原理相似,都以电泳技术为基础,区别在于具体的控制方式有所不同。依据传统电泳芯片驱动原理,分析了低电压电泳芯片的驱动原理,设计了十字形和螺旋形通道的两种低电压电泳芯片,并使用ANSOFT有限元软件对芯片进样和分离过程的电势、电场分布进行了仿真,验证了低电压驱动方式的可行性。分析了低电压电泳芯片通道深度、电极宽度、电极间距、绝缘材料及薄膜厚度等参数对通道内电场分布的影响,得出了芯片结构的优化参数。根据设计参数制作出低电压电泳芯片,使用磁控溅射法制作了铂金属阵列电极基片,利用湿法腐蚀工艺制作了玻璃盖片。分别选取硅和SU-8两种材料利用模具复制法制作了PDMS盖片,SU-8以其加工周期短、图形复制准确、微结构边缘陡直等优点,成为制作PDMS模具的最佳选择。为了解决严重制约低电压电泳芯片实际应用的气泡问题,采用在阵列电极表面制作绝缘薄膜的方案,开展了二氧化硅和PDMS两种绝缘薄膜的制备研究。使用电子束蒸发方法制作了二氧化硅绝缘膜,实验结果表明,在基片温度300℃条件下生长的4μm二氧化硅薄膜,可以承受500KV/cm场强,耐压200V,能够满足低电压电泳芯片应用的需要。采用旋涂法制作了PDMS绝缘薄膜,测试结果表明,厚度为4μm的PDMS可以承受560KV/cm的场强,耐压220V。从电绝缘特性可以看出,两种绝缘膜都适用于低电压电泳芯片的制作,但是PDMS绝缘膜与二氧化硅薄膜相比,具有工艺简单、成本低廉等特点,因此芯片最终选用PDMS绝缘膜进行制作。直接固化的PDMS盖片和绝缘薄膜因材料的固有特性,表面能比较低,呈疏水性,不利于生物样品在通道内的移动,需要对PDMS表面进行亲水改性。实验采用臭氧紫外法对PDMS表面进行改性,并与无臭氧紫外方法的处理效果进行了对比,使用多种表征方法分析了改性机理。在相同的处理时间内,经臭氧紫外处理的PDMS表面水接触角更小,亲水性明显增强。红外光谱测试表明,臭氧紫外改性后的PDMS表面各种官能团变化较大,其中-CH3疏水基团随着处理时间的增加大幅减少,Si-OH和-OH两种亲水基团大量增加,并出现了二氧化硅的典型红外光谱峰。使用X射线衍射、扫描电镜与能谱测试的结果证明,PDMS表面改性后生成了类玻璃态二氧化硅物质,亲水基团的增多和二氧化硅物质的生成是PDMS表面亲水性显著增强的主要原因。实验结果表明,臭氧紫外处理方法是一种操作简单、低成本的PDMS亲水改性手段。设计并制作了低电压电泳芯片的电极控制系统。系统以STM32芯片为主控制器,结合驱动芯片、阵列光耦、放大滤波电路、D/A及A/D电路,实现对芯片阵列电极电压幅值、进样时间、电极切换的精确控制。研究并设计了以FPGA芯片为核心,包括激光器、CCD传感器、预处理电路的荧光检测系统,通过上位机数据处理程序,系统可以实现低电压电泳芯片样品检测和电泳谱图实时显示的功能。利用低电压电泳芯片、电极控制系统和荧光检测系统,组建了低电压电泳芯片分析系统。使用该系统进行了两种绝缘薄膜消除气泡效果的测试,选用罗丹明6G和罗丹明B溶液为样品,在十字形和螺旋形通道的低电压电泳芯片上分别进行了电泳分离实验。测试结果表明,二氧化硅和PDMS绝缘薄膜在样品电泳过程中完全抑制了通道内气泡的产生,两种低电压电泳芯片都可以在90V电压作用下实现样品的电泳分离。螺旋形通道低电压电泳芯片比十字形通道具有更好的分离效果,低浓度样品分离度大于1,两种样品能够完全分开。本文研制的低电压电泳芯片分析系统,在100V以内就可以实现样品电泳分离的功能,与传统电泳芯片近千伏的驱动电压相比,不仅工作电压下降了一个数量级,而且系统体积明显减小,为电泳芯片系统的进一步微型化与集成化奠定了良好基础。更多还原

【Abstract】 The microfluidic electrophoresis chip is an important part of micro total analysis systems (μTAS). They have some advantages including reduced reagent usage, decreased operation times and added capabilities, which was widely used in genome sequencing project, epidemic disease testing and drug screening. It has become a better research platform for the life science and chemical analysis field. But the injection and separation of samples in the conventional microfluidic electrophoresis chips system is to apply high voltage from several hundreds to thousand volts, there are some safety risks for operators and the large power equipment is difficult to integrate, which limit the microminiaturization and integration of chip system. Therefore, a proposal of developing the low voltage electrophoresis chip system has been given by some researches. However, this system is still in the stage of research, and there are several key techniques, which need to be solved before this kind chip is used for commercial purpose. They include the bubble issue, optimization of the chip structure, low cost of surface modification for the chip, manufacture of miniaturized control and detection system. To solve these problems, the research of key technologies for low voltage electrophoresis chip analysis system has been developed in this work.The principle based on the electrophoresis technique of sample driving for the low voltage electrophoresis chip is similar to the way of conventional electrophoresis chip, but the control mode is different. According to the theory of the conventional electrophoresis chip, the concept of the low voltage electrophoresis chip was proposed. The cross channel and helix channel low voltage electrophoresis chip were designed, and the finite element analysis software ANSOFT was using to simulate the potential and electric filed of the chips. The simulation result indicated the feasibility of the low voltage driving method. In addition, the parameters of the chip structure such as depth of the micro channel, the thickness of the insulation film, size and position of electrodes were optimized.The fabrication procedures for the low voltage electrophoresis chip were discussed in details. The arrayed Pt electrodes were deposited on a piece of glass by magnetron sputtering. The glass cover was using wet etching method. The PDMS cover was fabricated by mold replication technology, which using silicon and SU-8mold. By comparison, SU-8mold has the advantages of short cycle time manufacturing, high precision, vertical edge, which became the best choice. In order to eliminate bubbles in the channel of low voltage electrophoresis chip, the PDMS film and the silicon dioxide film as the insulation film were proposed deposited on the Pt electrodes. Simultaneously, the electrical and structural characteristics of the two kind films were investigated. SiO2film was deposited by electron-beam evaporation. Experiment results showed that the surface of SiO2film became smooth and uniform for the growth temperature at300℃, the breakdown electric field strength was500KV/cm and the breakdown voltage was200V for the thickness of the film at4μm. The breakdown strength and breakdown voltage of the PDMS film with the same thickness was560KV/cm and220V. The electric insulation property of the two films is close, but PDMS film has low cost and simple manufacturing process.PDMS is a hydrophobic material, which makes a difficult transferring sample solution in the channel of electrophoresis chips, so the PDMS is needed to improve the surface hydrophily for decreasing non-specific adsorption of hydrophobic. In this work, UV/ozone method was utilized to hydrophilize the surface of PDMS and compared to UV method. Contact angle measurements show that the hydrophilic of the PDMS sample by UV/ozone was significantly enhanced compared with UV method within the same time. The results of FTIR spectroscopy indicate that many chemical functional groups of PDMS surface have been changed by UV/ozone modification,-CH3hydrophobic group gradually decreased with the time,-OH and Si-OH hydrophilic groups increased obviously, and the characteristic peaks of SiO2gradually appear. XRD and SEM/EDS results show that the glass-like SiCO2layer formed on the PDMS surface. The hydrophilic groups and SiO2layer are the main reason for the enhancement of the PDMS hydrophilic. The experiment results demonstrate that the UV/ozone treatment was a simple operation and low cost hydrophilic modification method.The control system for the arrayed electrodes of the low voltage electrophoresis chip was present. This system consists of STM32chip, driver chip, optocouplers, the amplifier-filter circuit, D/A and A/D circuit which controlled the switch time, driving mode and voltage output of the arrayed electrodes. The fluorescence detection system was designed for the low voltage electrophoresis chip that included a main control FPGA chip, CCD sensor, laser light source and pre-processing circuits. With the application software of the host PC, the detection system could test the sample and realize the real-time display of the sample fluorescence spectra.The low voltage electrophoresis chip, control system, detection system constituted the whole sample analysis system. The Rhodamine B and Rhodamine6G as the sample were used in the electrophoresis separation experiments on the two kind low voltage electrophoresis chips. Test results show that the electrophoresis separation of the sample was achieved by applying voltage90V on the two chips. In addition, the helix channel chip has better separation than the cross channel chip, and the degree of separation for the low concentration sample was more than one. The sample can be successfully separated below the100V using the low voltage electrophoresis chip system in this work. Compare with the conventional electrophoresis chips system, the applied voltage declined an order of magnitude and the size became smaller. This work will lay the foundation for the further miniaturization, integration of the electrophoresis chip system.更多还原