Rails and anchors: guiding and trapping droplet microreactors in two dimensions
Rails and anchors: guiding and trapping droplet microreactors in two dimensions
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DOI：
10.1039/c01c00104j
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发表时间：
2011-01-01
期刊：
影响因子：
6.1
通讯作者：
Baroud, Charles N.
中科院分区：
文献类型：
--
作者：
Abbyad, Paul;Dangla, Remi;Baroud, Charles N.
本文提出了一种通过在通道顶面蚀刻精细图案来控制纳升液滴在又宽又薄的微通道中运动的方法。对于被通道顶部挤压的液滴来说，这种控制是可能的，通过允许它们在进入局部凹陷时降低其表面能。由此产生的表面能增益将液滴拉入凹槽，使得局部孔可以用作固定液滴的锚，而线性图案可以用作轨道以引导它们沿着复杂的轨迹移动。只要驱动流速低于取决于孔和液滴尺寸的临界值，锚定液滴就可以无限期地保持静止。通过将孔微加工成网格图案，液滴可以排列并保持在显微镜的观察视野中，对抗平均载流。然后可以通过与流动的载体油进行气体交换来调节它们的含量。我们特别演示了如何在空间和时间上控制液滴内的 pH 值或氧气水平，方法是将成排的液滴暴露于不同气体浓度的两股油流中，或者通过定期切换油输入以随时间改变液滴的气体浓度。氧气控制用于选择性地使包裹镰状细胞病患者红细胞的液滴脱氧，以研究细胞内血红蛋白的聚合。锚定液滴的氧合和脱氧循环引起血红蛋白的解聚和聚合，从而提供了一种模拟生理流中发生的循环的方法。
This paper presents a method to control the motion of nanolitre drops in a wide and thin microchannel, by etching fine patterns into the channel's top surface. Such control is possible for drops that are squeezed by the channel roof, by allowing them to reduce their surface energy as they enter into a local depression. The resulting gain in surface energy pulls a drop into the groove such that localized holes can be used as anchors for holding drops, while linear patterns can be used as rails to guide them along complex trajectories. An anchored drop can remain stationary indefinitely, as long as the driving flow rate is below a critical value which depends on the hole and drop sizes. By micro-fabricating holes into a grid pattern, drops can be arrayed and held in the observation field of a microscope against the mean carrier flow. Their contents can then be modulated by gas exchange with the flowing carrier oil. We demonstrate in particular how the pH or the oxygen levels within the drops can be controlled spatially and temporally, either by exposing rows of drops to two streams of oil at different gas concentrations or by periodically switching oil inputs to vary the gas concentration of drops as a function of time. Oxygen control is used to selectively deoxygenate droplets that encapsulate red blood cells from patients suffering from sickle cell disease, in order to study the polymerization of intracellular hemoglobin. Cycles of oxygenation and deoxygenation of anchored droplets induce depolymerization and polymerization of the hemoglobin, thus providing a method to simulate the cycling that takes place in physiological flows.