U or C-shaped waveguides, coupled to analyte microchannels, have been shown to be very responsive to evanescent-wave-absorption-based sensing. However, due to only having a single C-bend length, for analyte interaction in earlier devices, there was always an opportunity to advance their evanescent-absorbance sensitivity, by including multiple C-bend structures (interfaced with the analyte microchannel system) in the device design. To achieve this objective, two different types of waveguide probes (having a different orientation of two C-bends), i.e. S-bend and spiral-bend, were theoretically analyzed and further, experimentally tested for their comparative sensitivity to evanescent wave absorption, in this pioneering study. A novel single-step fabrication procedure (using an SU-8 photoresist), was executed to fabricate these waveguide structures interfaced (both at their inner and outer bend surfaces) with a microchannel system, along with fiber-to-waveguide coupler structures. Experimentally, the sensitivity of the S-bend waveguides was found to be ∼25% higher compared to that of spiral waveguides of similar dimensions, which corroborated the results from numerical modeling. Compared to our earlier embedded C-bend waveguides, the overall evanescent-wave-absorption-based detection sensitivity of the embedded spiral and S-bend waveguides were found to be improved by ∼7.5 times and ∼9 times respectively. Finally, these devices were found to be ideally suited for more sensitive biological-, as well as, chemical-sensing applications, provided a suitable surface alteration process is performed to these waveguide probes. Further, the proposed device has a possible capability for: facile continuous (real-time) analysis, a fixed sample volume interaction, and control over the evaporation of analyte samples introduced in to the device.

中文翻译：

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研究耦合到微通道系统的双弯曲蛇形/螺旋波导，用于有效的、基于渐逝波吸收的片上生物/化学传感应用†

与分析物微通道耦合的 U 形或 C 形波导已被证明对基于倏逝波吸收的传感非常敏感。然而，由于只有一个 C 弯长度，对于早期设备中的分析物相互作用，总是有机会通过在设备中包含多个 C 弯结构（与分析物微通道系统接口）来提高其倏逝吸收灵敏度。设备设计。为了实现这一目标，两种不同类型的波导探头（具有两个 C 形弯的不同方向），即在这项开创性的研究中，对 S 弯曲和螺旋弯曲进行了理论分析，并进一步通过实验测试了它们对倏逝波吸收的比较敏感性。执行了一种新颖的单步制造程序（使用 SU-8 光刻胶）来制造这些与微通道系统接口（在其内部和外部弯曲表面）的波导结构，以及光纤到波导耦合器结构。实验上，发现 S 弯波导的灵敏度比类似尺寸的螺旋波导高 25%，这证实了数值模拟的结果。与我们早期的嵌入式 C 弯曲波导相比，发现嵌入式螺旋和 S 弯曲波导的整体基于倏逝波吸收的检测灵敏度提高了 ~7。分别为 5 次和～9 次。最后，发现这些设备非常适合更敏感的生物和化学传感应用，前提是对这些波导探针执行合适的表面改变过程。此外，所提出的装置具有以下可能的能力：易于连续（实时）分析、固定样品体积相互作用以及对引入装置中的分析物样品的蒸发进行控制。