Abstract

Microfluidics has enabled low volume biochemistry reactions to be carried out at the point-of-care. A key component in microfluidics is the microfluidic valve. Microfluidic valves are not only useful for directing flow at intersections but also allow mixtures/dilutions to be tuned real-time and even provide peristaltic pumping capabilities. In the transition from chip-in-a-lab to lab-on-a-chip, it is essential to ensure that microfluidic valves are designed to require less peripheral equipment and that they are transportable. In this paper, a thermally-actuated microfluidic valve is presented. The valve itself is fabricated with off-the-shelf components without the need for sophisticated cleanroom techniques. It is shown that multiple valves can be controlled and operated via a power supply and an Arduino microcontroller; an important step towards transportable microfluidic devices capable of carrying out analytical assays at the point-of-care. It is been calculated that a single actuator costs less than $1, this highlights the potential of the presented valve for scaling out. The valve operation is demonstrated by adjusting the ratio of a water/dye mixture in a continuous flow microfluidic chip with Y-junction channel geometry. The power required to operate one microfluidic valve has been characterised both theoretically and experimentally. Cyclical operation of the valve has been demonstrated for 65 h with 585 actuations. The presented valve is capable of actuating rectangular microfluidic channels of 500 μm × 50 μm with an expected temperature increase of up to 5 °C. The fastest actuation times achieved were 2 s for valve closing (heating) and 9 s for valve opening (cooling).

Highlights

  • IntroductionThey can be used for switching or adjusting flows between chemicals in a Y-junction geometry[3,4], for mixing chemicals[5,6], and for peristaltic pumping[7]

  • Engineered valves lie at the heart of fluidics, especially microfluidics

  • This paper reports a low-cost, programmable, thermally-actuated microfluidic valve constructed using off-the-shelf components without requiring cleanroom facilities

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Summary

Introduction

They can be used for switching or adjusting flows between chemicals in a Y-junction geometry[3,4], for mixing chemicals[5,6], and for peristaltic pumping[7]. Microfluidic valves have been utilised for powerful applications such as immunoassays[14], drug screening[15], binding assays[6], nucleic acid purification[16], and microchip electrophoresis[17]. While these are great examples of assays carried out on chips in a lab, it is essential to work towards rendering these capabilities portable for point-ofcare applications. Various types of valves have been reported in the literature, categorised here based on three actuation types: pneumatic, mechanical, and thermal

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