Many routine genomic-analysis assays rely on gel electrophoresis to perform size-selective fractionation of DNA fragments in the size range below 1 kb in length. Over the past decade, impressive progress has been made towards the development of microfabricated electrophoresis systems to conduct these assays in a microfluidic lab-on-a-chip format. Since these devices are inexpensive, require only nanolitre sample volumes, and do not rely on the availability of a pre-existing laboratory infrastructure, they are readily deployable in remote field locations for use in a variety of medical and biosensing applications. The design and construction of microfabricated electrophoresis devices poses a variety of challenges, including the need to achieve high-resolution separations over distances of a few centimetres or less, and the need to easily interface with additional microfluidic components to produce self-contained integrated DNA-analysis systems. In this paper, we review recent efforts to develop devices to satisfy these requirements and live up to the promise of fulfilling the growing need for inexpensive portable genomic-analysis equipment.

Although advances in microfluidic technology have enabled increasingly sophisticated biosensing and bioassay operations to be performed at the microscale, many of these applications employ such small amounts of charged biomolecules (DNA, proteins, and peptides) that they must first be preconcentrated to a detectable level. Efficient strategies for precisely handling minute quantities of biomolecules in microchannel geometries are critically needed; however, it has proven challenging to achieve simultaneous concentration, focusing, and metering capabilities with current-generation sample-injection technology. By using microfluidic chips incorporating arrays of individually addressable microfabricated electrodes, we demonstrate that DNA can be sequentially concentrated, focused into a narrow zone, metered, and injected into an analysis channel. This technique transports charged biomolecules between active electrodes upon application of a small potential difference (1 V) and is capable of achieving orders of magnitude concentration increases within a small device footprint. The collected samples are highly focused, with sample zone size and shape defined solely by electrode geometry.sample injection ͉ microfabrication ͉ microfluidics ͉ lab on a chip

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Mit bloßem Auge sichtbar: Ein Wechselspiel zwischen Elektrophorese und Elektrochemie kann genutzt werden, um makromolekulare Spezies wie DNA, Proteine oder Cyclodextrane an einer Elektrodenoberfläche zu kompaktieren und gleichzeitig den Molekülfilm mittels Gasblasen aus einer lokalen elektrochemischen Reaktion aufzublähen. Der kompaktierte Film ist selbst bei unmarkierten Proben unter gewöhnlichem weißem Licht sichtbar, woraus sich eine markierungsfreie Technik für den Nachweis von Makromolekülen wie DNA, Proteinen und Cyclodextranen ergibt.