Showing papers by "Abraham D. Stroock published in 2000"
TL;DR: In this article, the authors quantified both experimentally and theoretically the diffusion of low-molecular-weight species across the interface between two aqueous solutions in pressure-driven laminar flow in microchannels at high Peclet numbers, showing that the width of reaction-diffusion zone at the interface adjacent to the wall of the channel and transverse to the direction of flow scales as the one-third power of both the axial distance down the channel (from the point where the two streams join) and the average velocity of the flow, instead
Abstract: This letter quantifies both experimentally and theoretically the diffusion of low-molecular-weight species across the interface between two aqueous solutions in pressure-driven laminar flow in microchannels at high Peclet numbers. Confocal fluorescent microscopy was used to visualize a fluorescent product formed by reaction between chemical species carried separately by the two solutions. At steady state, the width of the reaction–diffusion zone at the interface adjacent to the wall of the channel and transverse to the direction of flow scales as the one-third power of both the axial distance down the channel (from the point where the two streams join) and the average velocity of the flow, instead of the more familiar one-half power scaling which was measured in the middle of the channel. A quantitative description of reaction–diffusion processes near the walls of the channel, such as described in this letter, is required for the rational use of laminar flows for performing spatially resolved surface chemistry and biology inside microchannels and for understanding three-dimensional features of mass transport in shearing flows near surfaces.
558 citations
TL;DR: This Letter reports the measurement of electro-osmotic flows (EOF) in microchannels with surface charge patterned on the 200 microm scale, which agree well with theory in the limit of thin double layers and low surface potential.
Abstract: This Letter reports the measurement of electro-osmotic flows (EOF) in microchannels with surface charge patterned on the 200 mu m scale. We have investigated two classes of patterns: (1) Those in which the surface charge varies along a direction perpendicular to the electric field used to drive the EOF; this type of pattern generates multidirectional flow along the direction of the field. (2) Those in which the surface charge pattern varies parallel to the field; this pattern generates recirculating cellular flew, and thus causes motion both parallel and perpendicular to the external field. Measurements of both of these flours agree well with theory in the Limit of thin double layers and low surface potential.
309 citations
59 citations
28 citations
01 Jan 2000
TL;DR: In this article, a diffusive broadening of a low molecular weight species in pressure driven flow is studied using both experiment and numerical analysis, where confocal microscopy allows experimental visualization of the three dimensional nature of the diffusion.
Abstract: Diffusive broadening of a low molecular weight species in pressure driven flow is studied using both experiment and numerical analysis. Confocal microscopy allows experimental visualization of the three dimensional nature of the diffusion. Numerical results support the experimental results, and are used to provide insight into design questions about devices involving diffusive mixing.
8 citations