At Bielefeld University of Applied Sciences, a research team is working on improving the morphology of electrospun nanofiber nonwovens. These fascinating fine textiles could be important components for computers of the future.
A computer that works according to the same principle as the human brain: super-fast, extremely energy-efficient, that can learn and forget again, and has also been manufactured in a very resource-efficient way. At the moment, this sounds like science fiction, but neuromorphic computing is making rapid progress in science. One of the materials from which these thinking machines of the future can be made is already being produced and continually improved by a research team at Bielefeld University of Applied Sciences (UAS), Bielefeld/Germany.
With a Nanospider electrospinning machine from Elmarco various kinds of nanofiber mats can be produced at the university. The 60 × 80 × 180 cm3 device essentially consists of a lot of free space behind glass. At the bottom, a box filled with honey-like liquid runs back and forth on a metal wire. This is polyacrylonitrile dissolved in non-toxic dimethyl sulfoxide.
The essential part, however, is invisible: a strong electric field. This, in conjunction with the surface tension of the polymer solution, ensures that the droplets fly from the bottom upwards, forming threads that are between 100 and 300 nm thin, while the solvent evaporates. A nanometer, or a billionth of a meter, is really small: In relation to 1 meter, its size is like the diameter of a hazelnut in relation to that of the earth.
The whole thing works a bit like making cotton candy. The result is an ultra-light textile – 0.5 m wide – that can also be rolled up, and just like cotton candy, it sticks to the fingers very well, but because of the electrostatic charge.
The best bit about the nanofiber mats produced in Bielefeld are the magnetic particles with which they are studded. These particles give the nanofiber mats very specific properties that are highly useful for many applications. The big challenge is to distribute the particles as evenly as possible because they tend to form clumps due to the magnetic attraction.
Another important sign of the quality of nanofiber mats is their morphological structure. How thin are the threads? How strongly are they connected? How uniform is the resulting pattern? But this is not visible to the naked eye, of course. That is why the researchers are working with scanning electron microscope images.
To the untrained eye, the images look like bizarre, jungle-like webs. Experts recognize the success or failure of their work in the images. Above all, their work consists of testing, testing and testing again. The researchers are constantly looking for the best possible electrospinning parameters for certain polymers. The applied electrical voltage, the composition of the solvent, the distance of the electrodes, temperature and humidity – all these have an effect on the nanofiber mats’ structure. It even makes a difference whether it is summer or winter.
In the magazine “Magnetochemistry” Al Mamun and Dr. Lilia Sabantina from the Bielefeld UAS published the article “Investigation of the Morphological Structure of Needle-Free Electrospun Magnetic Nanofiber Mats”. The Bielefeld research team’s work also contributes to the further development of neuromorphic computing. Functionalized nanofiber mats are a possible approach for the hardware. They contain numerous nodes, can be magnetically or electrically conductive and can also realize learning and forgetting by using shape memory polymers, for example.
In today’s computers, the memory and processor are separate components. Data transport between them is a bottleneck that limits computing power and also increases power demand. This problem could be solved if data were stored and processed in the same area, as they are in the human brain. This is the basis for neuromorphic computers whose chips mimic neurons and synapses. Depending on the task at hand, they are much faster and ideally several orders of magnitude more energy-efficient than today’s computers. For artificial intelligence, image processing, autonomous driving and other complex real-time tasks, in particular, neuromorphic computers are more suitable than conventional computers.
However, there is a whole range of other applications for nanofiber nonwovens. They are an ideal material for growing cells. They shield sensitive laboratory equipment from magnetic radiation. They filter undesired substances from air and water. Furthermore, they could help people in rehabilitation improve the functionality of their fingers.
That’s what Al Mamun and Lilia Sabantina will be working on next. As part of a start-up with 2 other colleagues, a therapy vest for people with disabilities shall be developed. On this vest, there will be zips, hooks, buttons and various tactile surfaces where patients can train their fingers and their musculoskeletal system. Moreover, the nanofiber nonwovens serve as sensors to measure the therapy’s success.