Honey, I shrunk the coils

Voxalytic makes micro solenoids. These electronic parts made by a company launched from the University of Freiburg’s Department of Microsystems Engineering can be used to build machines which can MRI-scan very small samples. Researchers can use them to test and analyze tiny amounts of valuable substances or cells. Yet the Voxalytic microcoils can do much more than that. They may soon be able to improve energy management in phones and tablets.

Tiny but amazing: The company’s microcoils can enable the production of devices which carry out nuclear magnetic resonance analyses of very small samples.
Photo: Markus Breig

“Coils keep our whole world running,” says Professor Dr Ulrike Wallrabe. The director of the Department of Microsystems Engineering (IMTEK) is one of Voxalytic’s three founders. “Ever since Michael Faraday discovered the generator in 1831 - and how to produce electricity - it has been impossible to imagine a world without coils,” she says. These basic electrical parts are in the motors of pumps and window lifts, in dynamos, loudspeakers, MRIs and countless other machines. Up to now, such coils were relatively large. Voxalytic has shrunk the coils and now aims to conquer the microworld. The company’s microcoils enable the production of devices which can carry out nuclear magnetic resonance analyses of very small samples. That alone opens up many fields of application in research and industry. But Wallrabe and her team already have their eye on other uses for their products - the microcoils can be used in laptops, smartphones and other devices with small electronic components.

Voxalytic’s microtransformers, which convert voltages, could be used in phones and tablets.
Photo: Markus Breig

Rounding leads to inaccuracies

In research some substances and cell lines - particularly newly developed ones - are more valuable than platinum or gold. During the developmental phase, the use of such substances must be kept to a minimum - yet when it comes to key magnetic resonance analyses, the technology has its limitations. “The coil in the machines which excites the nuclei needs to be about the size of the sample to be analyzed,” Wallrabe explains. Only then can a high resolution be achieved. Until now it was difficult to get coils even in the millimeter range. Voxalytic’s microcoils are even tinier; the smallest is a mere tenth of a millimeter in size. It enables analysis of samples with a volume of a nanoliter. That’s one-millionth of a liter. With its help, researchers can conduct more tests and still save on the material. It also produces less waste. Voxalytic was founded in 2014; today it collaborates with half a dozen technology companies.

“I would like for us to become suppliers of the best microcoils, to permeate and dominate the market,” Wallrabe, who is IMTEK’s Professor of Microactuators. Put simply, coils are spirals of wire wound around a core. The roundness creates a problem for the microsystems engineers. The lithography process used for chips and other media can only create microstructures with straight walls - known as Manhattan structures. Voxalytic purchased a wire bonding machine which is usually used to connect microchips with very fine wires. “We redesigned it and got it to wind 0.03 millimeter thin, insulated copper or gold wires onto a bobbin,” Wallrabe says. The number of loops, and thereby the effectiveness, can be altered, as can the diameter, the wall thickness, and the height of the bobbin. The bobbin is usually a polymer cup of 0.1 to one millimeter in diameter. It serves simultaneously as a receptacle for the sample to be analyzed.

Little funding for experienced researchers

Magnetic resonance imaging machines contain several sets of bobbins - the thickest must create very strong magnetic fields, and they make all MRI machines large. Then there are the radio-frequency bobbins. They briefly alter the nuclear spin of the samples and measure how the original state is restored. The radio frequency cores may be large or small, depending on the size of the sample. This is where the Voxalytic microcoils come in. The two types of bobbins are usually enough for chemical research and development. The experts call it NMR (Nuclear Magnetic Resonance). The technique provides data on the spatial position of the control points. The results cannot be assembled into images. This is why medical MRI scanners need a third set of bobbins.

“At engineering faculties you eventually arrive at the point where you want to implement what you are researching,” says Ulrike Wallrabe of the startup. “But the main impetus came from Jan Korvink.” He is a micro-nuclear resonance expert who worked at IMTEK until 2015, before going to the Karlsruhe Institute of Technology (KIT), where he is the head of the Institute of Microstructures Technology. The third founder, Dr. Jörg Funk, brings engineering and economics expertise to the company. “We are a team of experienced people,” Wallrabe stresses. That can sometimes be a disadvantage. EXIST, Germany’s key grants scheme for startups, is only available to junior researchers. “There is barely any funding for us,” says Wallrabe. But the university rents them space and equipment on favorable terms.

“At engineering faculties you eventually arrive at the point where you want to implement what you are researching,” says Ulrike Wallrabe, one of the founding trio of Voxalytic.
Photo: Markus Breig

Microtransformers for phones and tablets

Wallgrabe was surprised at the administrative burden of establishing a business. “But what astonished me the most was how many swindlers try to cheat inexperienced entrepreneurs!” she says. Voxalytic did not fall for the letters and emails from fake authorities. The company is currently working to optimize a few stages of production. “Our focus at the moment is on the life sciences, chemicals and pharmaceuticals industry,” Wallrabe says. At the same time Voxalytic is already using its microcoils to make microtransformers. Many components in hand-held devices need different input voltages and have to have their own, larger transformers. Voxalytic plans to shrink and improve them too - one day. But right now the MRI machines have top priority: Ulrike Wallrabe hopes Voxalytic will dominate the market within the next five years.

Jürgen Schickinger