Abstract
Microfluidics offer microenvironments for reagent delivery, handling, mixing, reaction, and detection, but often demand the affiliated equipment for liquid control for these functions. As a helpful tool, the capillary pressure control valve (CPCV) has become popular to avoid using affiliated equipment. Liquid can be handled in a controlled manner by using the bubble pressure effects. In this paper, we analyze and categorize the CPCVs via three determining parameters: surface tension, contact angle, and microchannel shape. Finally, a few application scenarios and impacts of CPCV are listed, which includes how CPVC simplify automation of microfluidic networks, work with other driving modes; make extensive use of microfluidics by open channel, and sampling and delivery with controlled manners. The authors hope this review will help the development and use of the CPCV in microfluidic fields in both research and industry.
Highlights
Microfluidic technology has made great progress in the past two decades, and is a significant feature in a wide range of scientific and industrial work [1,2]
We focus on capillary pressure control valve (CPCV) descriptions through the whole article
Due to the capillarity property generated by surface tension, water is pulled into a microchannel with a hydrophilic surface inside, but it meets the stop barrier at the hydrophobic surfaces
Summary
Microfluidic technology has made great progress in the past two decades, and is a significant feature in a wide range of scientific and industrial work [1,2]. The capillary pressure control valve (CPCV) is a kind of passive valve that relies on the Laplace pressure generated by the change of the liquid front meniscus concavity. CPCVs do not require external equipment and rely solely on Laplace pressure at the liquid interfaces, which depends on the surface tension, contact angle and channel shape. We analyzed the CPCV examples from three fundamental elements: surface tension, contact angle and different microchannel shape We hope it can give a direction describing the specific phenomena theoretically and for other academic and industrial control valves research, which can have more useful applications. Part 2 is for the categories of CPCV and different three determining parameters of Laplace pressure, including surface tension, contact angle as well as microchannel shape.
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