Abstract：
Surface enhanced Raman spectroscopy (SERS) utilizes the fingerprint features of molecular vibrations to identify and detect substances. However, in traditional single focus excitation scenarios, its signal collection efficiency of the objective is restricted. Furthermore, the uneven distribution of samples on the SERS substrate would result in poor signal stability, while the excitation power is limited to avoid sample damage. SERS detection system always requires precise adjustment of focal length and spot size, making it difficult for point-of-care testing applications. Here, we proposed a SERS microfluidic chip with barium titanate microspheres array (BTMA) embedded using vacuum self-assembled hot-pressing method for SERS detection with simultaneous enhancement of sensitivity and stability. Due to photonic nano-jets and directional antenna effects, high index microspheres are perfect micro-lens for effective light focusing and signal collecting. The BTMA can not only disperse excitation beam into an array of focal points covering the target uniformly with very low signal fluctuation, but enlarge the power threshold for higher signal intensity. We conducted a proof-of-principle experiment on chip for the detection of bacteria with immuno-magnetic tags and immuno-SERS tags. Together with magnetic and ultrasonic operations, the target bacteria in the flow were evenly congregated on the focal plane of BTMA. It demonstrated a limit of detection of 5 cells/mL, excellent signal reproducibility (error∼4.84%), and excellent position tolerance of 500 μm in X-Y plane (error∼5.375%). It can be seen that BTMA-SERS microfluidic chip can effectively solve the contradiction between sensitivity and stability in SERS detection.
摘要：
表面增强拉曼光谱（SERS）利用分子振动的指纹特征来识别和检测物质。然而,在传统的单焦点激励场景中，其目的的信号采集效率受到限制。此外，样品在SERS基底上的不均匀分布会导致信号稳定性差，同时限制激励功率以避免样品损坏。SERS检测系统总是需要精确调整焦距和光斑尺寸，这使得即时测试应用变得困难。这里,我们提出了一种采用真空自组装热压方法嵌入钛酸钡微球阵列（BTMA）的SERS微流控芯片，用于SERS检测，同时提高了灵敏度和稳定性。由于光子纳米射流和定向天线效应，高折射率微球是完美的微透镜，用于有效的光聚焦和信号收集。BTMA不仅可以将激发光束分散到均匀覆盖目标的焦点阵列中，并且信号波动非常低，但放大功率阈值以获得更高的信号强度。我们在芯片上进行了原理验证实验，以使用免疫磁性标签和免疫SERS标签检测细菌。连同磁性和超声波操作，流中的目标细菌均匀地聚集在BTMA的焦平面上。它显示了5个细胞/mL的检测限，优异的信号再现性(误差4.84%)，在X-Y平面上具有500μm的出色位置公差（误差〜5.375%）。可见BTMA-SERS微流控芯片能有效解决SERS检测中灵敏度与稳定性的矛盾。
