Pandiyan Vimal Prabhu, John Renu
Appl Opt. 2016 Jan 20;55(3):A54-9. doi: 10.1364/AO.55.000A54.
We propose a versatile 3D phase-imaging microscope platform for real-time imaging of optomicrofluidic devices based on the principle of digital holographic microscopy (DHM). Lab-on-chip microfluidic devices fabricated on transparent polydimethylsiloxane (PDMS) and glass substrates have attained wide popularity in biological sensing applications. However, monitoring, visualization, and characterization of microfluidic devices, microfluidic flows, and the biochemical kinetics happening in these devices is difficult due to the lack of proper techniques for real-time imaging and analysis. The traditional bright-field microscopic techniques fail in imaging applications, as the microfluidic channels and the fluids carrying biological samples are transparent and not visible in bright light. Phase-based microscopy techniques that can image the phase of the microfluidic channel and changes in refractive indices due to the fluids and biological samples present in the channel are ideal for imaging the fluid flow dynamics in a microfluidic channel at high resolutions. This paper demonstrates three-dimensional imaging of a microfluidic device with nanometric depth precisions and high SNR. We demonstrate imaging of microelectrodes of nanometric thickness patterned on glass substrate and the microfluidic channel. Three-dimensional imaging of a transparent PDMS optomicrofluidic channel, fluid flow, and live yeast cell flow in this channel has been demonstrated using DHM. We also quantify the average velocity of fluid flow through the channel. In comparison to any conventional bright-field microscope, the 3D depth information in the images illustrated in this work carry much information about the biological system under observation. The results demonstrated in this paper prove the high potential of DHM in imaging optofluidic devices; detection of pathogens, cells, and bioanalytes on lab-on-chip devices; and in studying microfluidic dynamics in real time based on phase changes.
我们基于数字全息显微镜（DHM）原理，提出了一种用于光微流控器件实时成像的多功能三维相成像显微镜平台。在透明聚二甲基硅氧烷（PDMS）和玻璃基板上制造的芯片实验室微流控器件在生物传感应用中已广泛普及。然而，由于缺乏用于实时成像和分析的合适技术，对微流控器件、微流控流动以及这些器件中发生的生化动力学进行监测、可视化和表征变得困难。传统的明场显微镜技术在成像应用中失效，因为微流控通道和携带生物样品的流体是透明的，在强光下不可见。基于相位的显微镜技术可以对微流控通道的相位以及由于通道中存在的流体和生物样品引起的折射率变化进行成像，非常适合以高分辨率对微流控通道中的流体流动动力学进行成像。本文展示了具有纳米级深度精度和高信噪比的微流控器件的三维成像。我们展示了在玻璃基板上图案化的纳米厚度微电极以及微流控通道的成像。利用DHM展示了透明PDMS光微流控通道、流体流动以及该通道中活酵母细胞流动的三维成像。我们还对通过通道的流体流动平均速度进行了量化。与任何传统的明场显微镜相比，本文所示图像中的三维深度信息携带了更多关于所观察生物系统的信息。本文展示的结果证明了DHM在光流体器件成像、芯片实验室器件上病原体、细胞和生物分析物的检测以及基于相位变化实时研究微流控动力学方面具有很高的潜力。
