Behavior of capillary valves in centrifugal microfluidic devices prepared by three-dimensional printing |
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Authors: | Jessica L Moore Austin McCuiston Isaac Mittendorf Rudy Ottway R Daniel Johnson |
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Affiliation: | (1) Department of Chemistry, Murray State University, Murray, KY 42071-3300, USA;(2) Department of Industrial and Engineering Technology, Murray State University, Murray, KY 42071-3300, USA; |
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Abstract: | This paper details the behavior of capillary valves in centrifugal microfluidic devices prepared by three-dimensional (3D),
or solid-object, printing. Microfluidic structures containing valve channels with different widths, heights, and radial distances
from the center of rotation were studied and compared with extant capillary valve theories. Due to the printing process, the
produced valve channels possessed a ridged or “scalloped” pattern. Hence, actual channel widths at the widest and narrowest
points of the ridged pattern were determined, and used in comparisons between theoretical and empirical values. In addition,
variations in contact angle resulting from the ridged pattern were measured and employed in theoretical calculations. For
1-mm high valve channels, the critical angular frequency (rpm) required to overcome capillary valve pressure was found to
be independent of width. However, as the height of the valve channel was reduced, the critical rpm was found to become progressively
more width-dependent increasing more rapidly for narrower channels. Both of these observations point to a role for feature
sharpness, as well as the geometry of the valve channel opening, in valve behavior. Otherwise, valves followed a predictable
trend of increasing critical rpm with decreased valve height and decreased radial distance from the rotation center. Using
these results as a guide, then, it is possible to prepare centrifugal microfluidic devices by 3D printing with operability
comparable to devices prepared by other microfabrication techniques. |
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