多通道微流控芯片的光探测及系统集成化方法研究

	多通道微流控芯片的光探测及系统集成化方法研究
	周文超
学位类型	博士
导师	吴一辉
	2014-07
学位授予单位	中国科学院大学
学位专业	机械制造及其自动化
摘要	随着微纳米加工技术的发展，分析仪器逐渐朝着微型化、集成化和便携化方向发展，由于微流控芯片有望在微米尺度下实现样品的制备、分离、反应、检测等功能操作，现已成为目前分析仪器的重要研究方向和前沿。自此概念的提出至今已近20年，微流控芯片取得了长足发展。光学检测方法是微流控芯片最重要的检测方法之一，但是由于外部检测设备体积庞大、价格昂贵等因素，微流控芯片并没有实现在芯片上光学检测集成化这一最终目标。本论文主要针对微流控芯片高灵敏度光学检测和光学检测系统集成化而做的相关研究，主要研究内容包括：（1）针对生化分析微流控芯片全血中常用指标的高灵敏度多参数光学检测，提出了一种类法布里-珀罗共振腔的多次全反射探测腔结构，理论分析了取得最大有效光程和最佳信噪比的条件。研究表明，对于固定的探测腔体积，理论最大光程仅与入射光斑直径平方成反比，最佳信噪比则取决于镜面反射率和反射次数，并采用一种新的补偿方法解决了多次反射引起的一致性误差。设计了一探测腔结构，并实验测定了亚甲基蓝溶液、白蛋白试剂和葡萄糖试剂，实验结果均具有很高的线性度，有效光程提高了1-2个数量级。（2）滤光片是吸光度检测方法中一个重要的光学元件，但传统单片滤光片很难具有多波长滤波功能，为实现光学检测器件在微流控芯片上的阵列化和集成化，基于亚波长金属光栅的导模共振原理设计了一种新型滤光片。利用平板波导理论分析了滤光片波导对称和非对称结构的共振特性，数值计算了滤光片结构各个参数如光栅周期、占空比、入射光偏振特性、缓冲层厚度等对透射谱线的影响，研究表明此种新型的滤光片具有高透过率、偏振无关、易于集成等优点。（3）为了进一步提高光学检测系统与微流控芯片的集成度，本论文基于导模共振原理提出了一种实现超常吸收的新型结构，通过详细的理论分析可知，表面等离子激元耦合腔模与波导层内的准导模之间的耦合作用使得在最大吸收峰位置产生一个反交叉点，在该点附近入射光的能量重新分配，大部分能量集中在金属光栅周围从而被吸收。结果表明，吸收峰与光栅周期成正比，该吸收结构具有吸收率高、结构容差大等优点，这种结构可以有效地将滤光片和光电探测器相结合形成具有波长选择和高灵敏度的光电探测器件，提高了光学检测系统的集成度。（4）微流控芯片的集成意味着得尺寸大幅度减小，光程的减小必然会降低基于吸光度检测方法的灵敏度，为解决该问题，本论文提出了一种新型的慢光结构。旨在利用导模共振效应在共振波长产生相位突变，该结构相位的变化引起群折射率的急剧增大，从而实现慢光效应。数值计算分析了缓冲层厚度和光栅周期对于群折射率和相位的影响，将这种慢光结构和微流控芯片相结合有望将灵敏度提高2-3个数量级。
其他摘要	With the development of micro- and nano- fabrication technology, analysis instruments with miniaturization, integration and portability are becoming a new trend. Microfuidic chips can be integrated with the whole laboratory operation such as sampling, separation, reaction, detection on a single microchip, so the research on the microfluidic now represents the developing direction in analysis instruments field. After twenty years’ development since the concept was proposed, microfluidic has achieved great improvement. Optical detection is one of the most important detection manners. However, due to the larger volume and higher price of external equipments, microfuidic hasn’t realized so-called optical integrated detection completely. This thesis mainly is about how to improve the sensitivity of optical detection and integration of optical system on microfluidic chips. The related contents are as follows: (1) In order to realize highly sensitive and multi-parameter detection for the whole blood, a multireflection structure based on a quasi Fabry-Perot cavity was proposed. The optimal condition of the largest optical path and the proper Signal and Noise Ratio (SNR) was analyzed theoretically. The results indicate that the theoretical maximum path is only inversely proportional to the square of the beam diameter and the SNR is dependent on the reflectivity of the mirror and the number of the reflection. And a new compensating manner was presented to avoid the uniform error caused by the multireflection. A detection cavity was designed and methylene blue solutions, albumin and glucose were measured on a centrifugal microfluidic chip. The measured results have very good linearity and the optical path was proved to be improved by two orders. (2) Filter, as an important optical element in absorption detection, plays the key role in detecting different solutions. In order to achieve the miniature and integration of the optical devices on the microfluidic chips, a novel transmission filter based on subwavelength metallic grating guided-mode resonance is proposed. The resonance characteristics of the filters with symmetric and nonsymmetric waveguide structure were theoretically analyzed based on planar waveguide theory. The effects of the filter structural parameters on the transmission spectrum are investigated in detail, such as grating period, filling factor, the incident polarization, and buffer layer thickness. Simulated results show that the novel filters have high transmittance, polarization-independent, and high integration. (3) To improve the integration of the optical detection system and microfluidic chips further, a novel structure that can achieve extraordinary optical absorption based on guided-mode resonance effect was proposed. An anti-crossing point can be formed due to the coupling between the cavity mode and the quasi-guided mode at the maximum absorption peak. The resonant interaction between these two modes can influence the field distribution, which reinforces more power near the metal grating. From the simulation results, this structure has high absorption efficiency and good fabrication tolerances. The absorption peak can be readily tuned just by the grating period. The presented structure may combine the photodiode with the filter efficiently so that the integration of optical detection becomes simpler. (4) If the chips continue to reduce to the nano-scale, the optical path will decrease simultaneously. So the sensitivity will be very low. To solve this problem, a novel slow light structure was proposed in this thesis. The transmission peak has a narrow transparency window and is associated with a dramatic change in the transmission phase. An extremely slow group velocity of light traversing the structure can be obtained. The effects of buffer layer thickness and the grating period on the group index and the phase were investigated with the aid of rigorous coupling wave analysis. The sensitivity will be increase by three orders if we can combine the slow light structure and microfluidic chips.
语种	中文
文献类型	学位论文
条目标识符	http://ir.ciomp.ac.cn/handle/181722/41511
专题	中科院长春光机所知识产出
推荐引用方式 GB/T 7714	周文超. 多通道微流控芯片的光探测及系统集成化方法研究[D]. 中国科学院大学,2014.

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