Hydrodynamic focusing for vacuum-pumped microfluidics

Hydrodynamic focusing has proven to be a useful microfluidics technique for the study of systems under rapid mixing conditions. Most studies to date have used a "push" configuration, requiring multiple pumps or pressure sources that complicate implementation and limit applications in point-of-care environments. Here, we demonstrate a simplified hydrodynamic focusing approach, in which a single pump pulling at the device outlet can be used to drive hydrodynamic focusing with not only excellent control over the focus width and stream velocity, but also with minimal sample consumption. In this technique, flow can be either mechanically driven or induced simply through capillarity.[PUBLICATION ABSTRACT]