Matthiae Moritz, Kristensen Anders
Opt Express. 2019 Feb 4;27(3):3782-3790. doi: 10.1364/OE.27.003782.
Spatially offset Raman spectroscopy (SORS) enables one to distinguish chemical fingerprints of top and subsurface layers. In this paper, we apply SORS to a microfluidic two-layer system consisting of transparent liquid in a microchannel as the surface layer and microfluidic PDMS chip material as the sublayer. By using an imaging spectrograph connected to a microscope, we perform hyperspectral SORS acquisitions. Furthermore, the focus position z is translated. Thus, we combine the two methods of hyperspectral SORS and defocusing micro-SORS, which leads to an integral characterization of the layered system. The collected top and subsurface layers of Raman scattering at the optical axis (zero spatial offset) largely depends on the focus position z. However, the spatially offset Raman scattered intensity from the subsurface layer is constant for a large range of focus positions z. We claim that there is potential for internal referencing and alignment reproducibility. We demonstrate these findings experimentally in a microfluidic scenario where a 16 μm deep channel is filled with an aqueous hemoglobin solution. Our observation enables consistent concentration measurements in small-volume liquid samples.
空间偏移拉曼光谱（SORS）能够区分表层和次表层的化学指纹。在本文中，我们将SORS应用于一个微流体双层系统，该系统由微通道中的透明液体作为表层和微流体PDMS芯片材料作为次层组成。通过使用连接到显微镜的成像光谱仪，我们进行高光谱SORS采集。此外，焦点位置z会发生平移。因此，我们将高光谱SORS和散焦显微SORS这两种方法结合起来，从而对分层系统进行整体表征。在光轴（零空间偏移）处收集到的表层和次表层的拉曼散射在很大程度上取决于焦点位置z。然而，对于较大范围的焦点位置z，来自次表层的空间偏移拉曼散射强度是恒定的。我们认为存在内部参考和对准重现性的潜力。我们在一个微流体场景中通过实验证明了这些发现，在该场景中，一个16μm深的通道充满了血红蛋白水溶液。我们的观察结果使得能够对小体积液体样品进行一致的浓度测量。
