Zhu Hongying, White Ian M, Suter Jonathan D, Zourob Mohammed, Fan Xudong
Department of Biological Engineering, 240D Life Sciences Center, University of Missouri-Columbia, Columbia, Missouri 65211, USA.
Anal Chem. 2007 Feb 1;79(3):930-7. doi: 10.1021/ac061279q.
We developed a novel miniaturized and multiplexed, on-capillary, refractive index (RI) detector using liquid core optical ring resonators (LCORRs) for future development of capillary electrophoresis (CE) devices. The LCORR employs a glass capillary with a diameter of approximately 100 mum and a wall thickness of a few micrometers. The circular cross section of the capillary forms a ring resonator along which the light circulates in the form of the whispering gallery modes (WGMs). The WGM has an evanescent field extending into the capillary core and responds to the RI change due to the analyte conducted in the capillary, thus permitting label-free measurement. The resonating nature of the WGM enables repetitive light-analyte interaction, significantly enhancing the LCORR sensitivity. This LCORR architecture achieves dual use of the capillary as a sensor head and a CE fluidic channel, allowing for integrated, multiplexed, and noninvasive on-capillary detection at any location along the capillary. In this work, we used electro-osmotic flow and glycerol as a model system to demonstrate the fluid transport capability of the LCORRs. In addition, we performed flow speed measurement on the LCORR to demonstrate its flow analysis capability. Finally, using the LCORR's label-free sensing mechanism, we accurately deduced the analyte concentration in real time at a given point on the capillary. A sensitivity of 20 nm/RIU (refractive index units) was observed, leading to an RI detection limit of 10-6 RIU. The LCORR marries photonic technology with microfluidics and enables rapid on-capillary sample analysis and flow profile monitoring. The investigation in this regard will open a door to novel high-throughput CE devices and lab-on-a-chip sensors in the future.
我们开发了一种新型的小型化、多路复用的基于毛细管的折射率（RI）探测器，该探测器使用液芯光学环形谐振器（LCORR），用于毛细管电泳（CE）设备的未来发展。LCORR采用直径约100微米、壁厚几微米的玻璃毛细管。毛细管的圆形横截面形成一个环形谐振器，光以回音壁模式（WGM）的形式在其中循环。WGM具有延伸到毛细管芯中的倏逝场，并对毛细管中传导的分析物引起的RI变化做出响应，从而实现无标记测量。WGM的谐振特性实现了光与分析物的重复相互作用，显著提高了LCORR的灵敏度。这种LCORR结构实现了毛细管作为传感器头和CE流体通道的双重用途，允许在毛细管沿线的任何位置进行集成、多路复用和非侵入式的毛细管检测。在这项工作中，我们使用电渗流和甘油作为模型系统来展示LCORR的流体传输能力。此外，我们对LCORR进行了流速测量，以展示其流动分析能力。最后，利用LCORR的无标记传感机制，我们在毛细管上的给定位置实时准确地推断出分析物浓度。观察到灵敏度为20 nm/RIU（折射率单位），导致RI检测限为10-6 RIU。LCORR将光子技术与微流体技术相结合，实现了快速的毛细管样品分析和流动剖面监测。这方面的研究将为未来新型高通量CE设备和芯片实验室传感器打开一扇门。
