Authors: F.R. Phelan_Jr. and S.D. Hudson
Affilation: NIST, United States
Pages: 288 - 291
Keywords: Microfluidics, Four Roll Mill, Flow Classification, Finite Element Analysis, Linear Flow
The fluid dynamics of geometries for liquid state materials characterization in microfluidic devices are investigated. A pressure driven device using microchannels is sought that has an adjustable flow type, approximating the function of the four-roll mill. In particular, we investigate classes of channel flows in which the full range of linear flows (extension, shear and rotation) can be approximated in the neighborhood surrounding a stagnation point. To evaluate various candidate geometries, finite element flow simulations in the low Reynolds number limit were undertaken. Flow classification criteria were then used to delineate combinations of geometry and boundary conditions for which the flow type can be adjusted between extension, shear and rotation in the neighborhood surrounding the stagnation point, while providing adequate flow strength, and a stable environment for material observation. Two classes of flow geometries are identified. Both make use of opposing, laterally offset fluid streams that produce a stagnation point in the center of the geometry. In the first class, the flow type is manipulated by changing parameters inherent to the base geometry. This first case serves as a basis for identifying a second class in which the flow type is manipulated via changes in boundary conditions, while keeping the geometry constant.