University of Twente researchers have developed a way of separating DNA molecules using an electric field before capturing them on a chip.

The researchers found that when forced through extremely shallow channels just 20 nanometers deep an a few micrometers wide, DNA molecules behave very differently than when in free solution. In the latter situation, they tend to form clumps, whicle molecules in the channels are forced into an elongated straitjacket. This effect alone produces a difference in mobility between long and short molecules. Moreover, exposure to an electric field has now been shown to have a substaintial effect.

In a strong electric field, the molecules judder along the channel, while in weaker fields they move more smoothly, enabling DNA fragments to be ‘captured’ on a chip and separated for analysis.

A DNA module can easily by 1000 times longer than the channels are deep. As a result, it encounters minute surface irregularities at many different points, an effect that is reinforced by the electric field. This seems to be the cause of the stagnation in mobility that occurs in strong fields. It presents an opportunity to capture fragments; and using weaker fields, to accurately control their onward motion.

Full details of the research are to be published in Nano Letters.