Abstract: A method can include receiving a biological sample including the target cells, e.g., at an inlet of a microfluidic structure. This can involve flowing the target cells, e.g., suspended in a first buffer, at a first flow rate within a main channel of the microfluidic structure. At least one focusing flow can be applied to the biological sample, using a second buffer at a second flow rate, to help establish a boundary defining a central region or streamline. The central region can contain the target cells within the main channel and promote ion diffusion between the first and second buffers.

Abstract: This document provides integrated systems for controlling fluid flow in a fluidic device. Methods of using such systems are also described herein.