Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, ON M5S 3G8, Canada.
Lab Chip. 2012 Nov 21;12(22):4787-95. doi: 10.1039/c2lc40513j.
Capitalizing on the benefits of microscale segmented flows, e.g., enhanced mixing and reduced sample dispersion, so far requires specialist training and accommodating a few experimental inconveniences. For instance, microscale gas-liquid flows in many current setups take at least 10 min to stabilize and iterative manual adjustments are needed to achieve or maintain desired mixing or residence times. Here, we report a cruise control strategy that overcomes these limitations and allows microscale gas-liquid (bubble) and liquid-liquid (droplet) flow conditions to be rapidly "adjusted" and maintained. Using this strategy we consistently establish bubble and droplet flows with dispersed phase (plug) velocities of 5-300 mm s(-1), plug lengths of 0.6-5 mm and continuous phase (slug) lengths of 0.5-3 mm. The mixing times (1-5 s), mass transfer times (33-250 ms) and residence times (3-300 s) can therefore be directly imposed by dynamically controlling the supply of the dispersed and the continuous liquids either from external pumps or from local pressurized reservoirs. In the latter case, no chip-external pumps, liquid-perfused tubes or valves are necessary while unwanted dead volumes are significantly reduced.
利用微尺度分段流的优势，例如增强混合和减少样品分散，目前还需要专业培训和适应一些实验上的不便。例如，许多当前设置中的微尺度气-液流动至少需要 10 分钟才能稳定，并且需要迭代手动调整以达到或维持所需的混合或停留时间。在这里，我们报告了一种巡航控制策略，该策略克服了这些限制，并允许快速“调整”和维持微尺度气-液（气泡）和液-液（液滴）流动条件。使用该策略，我们一致地建立了具有分散相（塞子）速度为 5-300mm s(-1)、塞子长度为 0.6-5mm 和连续相（段塞）长度为 0.5-3mm 的气泡和液滴流。因此，混合时间（1-5 秒）、传质时间（33-250ms）和停留时间（3-300 秒）可以通过动态控制外部泵或局部加压储液器供应分散相和连续相来直接施加。在后一种情况下，不需要外部芯片泵、液体灌注管或阀门，同时显著减少了不需要的死体积。
