Young 4ever - the use of capillarity for passive flow handling in lab on a chip devices
Young 4ever - the use of capillarity for passive flow handling in lab on a chip devices
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DOI：
10.1039/b613839j
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发表时间：
2006-01-01
期刊：
影响因子：
6.1
通讯作者：
van den Berg, Albert
中科院分区：
文献类型：
--
作者：
Eijkel, Jan C. T.;van den Berg, Albert
当我们在实验室中处理日常流体时，如灌装、排空、计量和清洁，我们往往没有意识到我们使用的是一系列日常力量，因为它们总是在那里，因为它们只是不言而喻。这些力是重力、吸力和毛细管力，我们不需要复杂的设备就能应用它们。因此，除了用于流体处理之外，它们也是19世纪和20世纪实验室中用于分离和分析系统中液体推进的第一批力，例如，薄层色谱或试纸(从pH纸到临床试纸)中的毛细管力和液体色谱中的重力。除了这些处理流体的日常作用力之外，我们还可以加上离心力(例如，在手动台式离心机中)和蒸发。这些日常力量的现成使其特别适合诊断和护理点(POC)设备中的流体处理和推进。当这种体系小型化时，毛细管力的尺度最好，因为它作用在液体与通道壁的接触周长上，并且在向下缩放时，该周长相对于通道横截面积变得更大。因此，毛细诱导压力(单位通道面积的毛细压力)与特征通道尺寸成反比，如表1所示。传统上，纸张、织物、膜或网状物用于毛细推进和流量控制，例如在葡萄糖条中。然而，精确的流量控制和计量在这样的设备中可能是有问题的，因此在过去的几年中，人们对使用毛细管的微流控POC设备的兴趣激增。此外，在PoC设备领域之外，对在LOC设备中使用毛细管的兴趣最近也增加了。这篇焦点文章试图给出这一发展中的领域的概述，并将表明在1805年由Young和De Laplace描述的毛细现象中仍然有很大的潜力。
When we do our everyday fluid handling in the laboratory such as filling, emptying, metering and cleaning, we often don’t realize that we use a set of everyday forces that are ‘always there’because they just go without saying. These forces are gravity, suction and the capillary force, for the application of which we need no sophisticated equipment. Apart from their use for fluid handling they were therefore also the first forces to be used for liquid propulsion in separation and analysis systems in the 19th and 20th century laboratory, eg, the capillary force in thin layer chromatography or in test strips (from pH paper to clinical test strips) and gravity in liquid chromatography. To these everyday forces for fluid handling we could also add the centrifugal force (eg, in hand-operated bench top centrifuges) and evaporation. The ready availability of these everyday forces makes them particularly suited for fluid handling and propulsion in diagnostics and point-of-care (POC) devices. When such systems are miniaturized, the capillary force scales the best because it is exerted at the contact perimeter of liquid and channel wall, and the perimeter becomes larger relative to the channel cross-sectional area on downscaling. The capillarity-induced pressure, which is the capillary force per unit channel area, is therefore inversely proportional to the characteristic channel dimension as shown in Table 1. Classically, paper, fabric, membranes or mesh is used for capillary propulsion and flow control, for example in glucose strips. 1 Precise flow control and metering however can be problematic in such devices and the past few years have therefore seen a surge in interest in microfluidic POC devices employing capillarity. Also outside the area ofPOC devices the interest in the use of capillarity in LOC devices has recently increased. This Focus article attempts to give an overview of this developing field, and will show that there is still a lot of potential in the capillary phenomena described in 1805 by Young and de Laplace.