Microelectrodes offer a direct way to measure electrical signals in the brain or heart, however, the applications call for soft materials. In laboratory experiments, hard silicon-based designs affect cell organizations and shape, which can prompt inflammation and organ damage.
Researchers from the Technical University of Munich (TUM) took on this challenge, and were able to successfully print electrodes straight onto several delicious soft substrates—gummy bears.
Previous research used traditional, time-consuming production techniques that carried a hefty price tag. The TUM team streamlined the process, using a high-tech version of an inject printer. Carbon-based ink was used for the electrodes, and a neutral protective layer over the carbon paths shielded the sensor from stray signals.
“If you instead print the electrodes, you can produce a prototype relatively quickly and cheaply. The same applies if you need to rework it,” says TUM Professor of Neuroelectronics Bernhard Wolfrum. “Rapid prototyping of this kind enables us to work in entirely new ways.”
When searching for the right substrate, the researchers first tried a soft form of silicon known as PDMS (polydimethylsiloxane), and a biology experiment regular called agarose. They then looked to forms of gelatin, which included a gummy bear that was melted down and allowed to harden.
All the materials tested showed promising results for certain applications. Implants coated with gelatin, for example, were shown to reduce harmful chemical reactions within living tissue.
“The difficulty is in fine-tuning all of the components—both the technical set-up of the printer and the composition of the ink,” says Nouran Adly, the first author of the study. “In the case of PDMS, for example, we had to use a pre-treatment we developed just to get the ink to adhere to the surface.”
Soft materials armed with printable microelectrode arrays could help many areas, especially in the medical field.
“In the future, similar soft structures could be used to monitor nerve or heart functions in the body, for example, or even serve as a pacemaker,” says Prof. Wolfrum.
Still curious about the microelectrode-infused gummy bears? Check out the article, “Printed microelectrode arrays on soft materials: from PDMS to hydrogels,” published in npj Flexible Electronics, to learn more.