Trained drops

Canadian chemists have developed a technology that allows you to move liquid droplets along horizontal, vertical or inclined surfaces in almost any direction. Using the new technology, it will be possible to move droplets from cold to heat and vice versa, providing rapid heating or cooling of the liquid. The results of the work are published in the journal Lab on a Chip (Mohamed Abdelgawad et al, All-terrain droplet actuation).

The basis of the new technology, developed by scientists led by Aaron Wheeler from the University of Toronto, is a flexible polyimide surface, the shape of which can be arbitrarily changed. Electrodes are located on the entire surface area. The movement of liquid droplets is ensured by the sequential activation of pairs of electrodes, which leads to a decrease in the water-repellent properties of the surface in front of the drop. Accordingly, the drop moves forward.

The technology provides researchers with full control over the drop, allowing them to move it back and forth or up and down. You can see how the drops overcome obstacles on the roller.

In the picture:
(a) drop control scheme,
(b) the drop climbs to a 15-millimeter height,
(c) crosses the "bridge",
(d) climbs the "ladder",
(e) moves on a swirling surface and even
(f) on the down-facing side of the film.

The developers of the technology believe that it will be in demand in those areas where rapid fluid movement between different media is necessary. For example, the new principle can be used in molecular biology and biotechnology during polymerase chain reaction (PCR).

This reaction allows you to quickly "multiply" the necessary part of the DNA. During the passage of PCR, the test tube with the reaction mixture is repeatedly heated and cooled. Now rapid heating and cooling are provided by changing the temperature inside the device, where the test tubes are located. Wheeler suggests instead moving the reaction mixture – its volume usually does not exceed 50-100 microliters – from a hot test tube to a cold one.

Wheeler believes that the new technology can be used to carry out chemical catalysis or purification of DNA from organic mixtures. So far, he does not offer anything concrete, but he is sure that the prospects for using the new development are very broad.

Portal "Eternal youth" www.vechnayamolodost.ru based on the materials of "Lenta.Ru"

04.04.2008