DNA Focusing Using Microfabricated Electrode Arrays

Focusing methods are a key component in many miniaturized DNA analysis systems because they enable dilute samples to be concentrated to detectable levels while being simultaneously confined within a specified volume inside the microchannel. In this chapter, we describe a focusing method based on a device design incorporating arrays of addressable on-chip microfabricated electrodes that can locally increase the concentration of DNA in solution by electrophoretically sweeping it along the length of a microchannel. By applying a low voltage (1–2 V) between successive pairs of neighboring electrodes, the intrinsically negatively charged DNA fragments are induced to migrate toward and collect at each anode, thereby allowing the quantity of accumulated DNA to be precisely metered. We have characterized the kinetics of this process, and found the response to be robust over a range of different sample compositions and buffer environments.