New microdrives use light and heat

microcosm New microdrives use light and heat

Source: press release

Because in the micro world, not everything always works as we know it in everyday life, it offers many opportunities to discover new things. This time, it worked in the field of drive technology.

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New microdrives use light and heat
Junior professor Clarissa Schönecker at the Technical University of Kaiserslautern is investigating how microdrives can best be built in terms of efficiency and design. Light and heat are among the preferred tools. More about this here …

(Photo: TU Kaiserslautern / Koziel)

Junior professor Clarissa Schönecker (pictured), who heads the microfluidics department at Kaiserslautern University of Technology (TUK), works with fluid mechanics in miniaturized systems. Researchers in this sector are currently investigating whether and how directed movements in liquids can be generated at the miniature level using light or waste heat. This should be the basis for launching microsystem drives. The German Research Foundation (DFG) spends a total of 1.9 million euros on this.

Micro drives work differently

Special physical laws prevail in the micro world, says Schönecker. An example is that the smaller a pipeline is, its surface area increases relative to the interior space. Therefore, surface effects such as friction have a greater impact. It is said that this explains why drive concepts from our macro world do not work in microsystems. So you have to learn a different way of thinking.

“We are dealing with two different flow scenarios in microsystems,” says Schönecker. On the one hand with the fluid movement as it occurs relative to a surface. Just as required for pumping processes in pipelines. On the other hand, the researchers are testing a wide range of different transport vehicles that have to move in relation to a stationary liquid – so to speak, like a boat. There is already some discussion about such micro-swimmers in the research environment, because they could be used for mass transport in miniaturized applications, among other things.

Superhydrophobic surfaces propel

To enable the power to flow in microchannels, Schönecker and her working group use certain solids. These are special structures with so-called superhydrophobic (extremely water-repellent) surfaces. Supported by a special geometric design, they succeed in distributing the supplied heat in such a way that the liquid begins to move. The flow movement then occurs when the pronounced temperature gradient changes the surface tension of the liquid, whereby a tensile effect takes place, as it is said. This should help to understand how pump movements can be implemented in a microtechnical system. For example, it is conceivable that the waste heat from an electrically powered component in the future may be used to allow a coolant to flow.

New microboats do not need any chemicals

As for microswimmers, Schönecker also examines light or heat to cause movement. The subject of research is currently still miniature vehicles, to which a chemical reaction is taking place to set them in motion. “This means that the mini-transports depend on a fuel that either floats on the water surface or that they have to carry with them,” the scientist explains. Schönecker emphasizes, however, that their research approach does not require any chemistry. Instead, the microtransports locally changed the surface tension of the liquid in which they swam while warming up. This gives them – according to the same principle as above – the necessary drive. It is also important to clarify which design enables the micro-swimmers to perform directed movements and how they are best controlled. A confocal microscope with a fluorescence correlation spectroscopy function will also be purchased for this purpose.

In the first experiments with miniaturized thermal boats and other asymmetrically structured particles, movements under the influence of light or heat could already be detected, the researcher says.

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