Wolfrum and his team use a high-tech version of the inkjet printer. The electrodes are printed with carbonaceous liquid. To prevent the sensors from recording unwanted signals, a neutral protective layer is applied over the carbon tracks.
The researchers tested the method on various materials, including the soft silicone PDMS (polydimethylsiloxane), the substance agar, which is frequently used in biological experiments, and finally gelatine, including in the form of a melted and re-solidified jelly bear. Each of these substances has properties that are particularly suitable for certain applications. For example, gelatin-coated implants can reduce undesirable reactions in tissue.
The team was able to prove that the sensors deliver reliable values through experiments with cell cultures. With an average width of 30 micrometers, they also enable measurements on individual or few cells, which is difficult to achieve with established printing methods.
"The challenges lie in fine-tuning all components - both the printer's technical settings 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 resort to a pretreatment developed by us so that the ink would even adhere to the surface.
Printed soft microelectrode arrays could be used in various areas. They are not only suitable for a rapid prototyping approach in research, but could also change the treatment of patients. "In the future, similar soft structures could, for example, monitor nerve or heart function in the body or even serve as pacemakers," says Wolfrum. He and his team are currently working on printing more complex, three-dimensional microelectrode arrays. Secondly, they are investigating printable sensors that do not react to voltage fluctuations but selectively to chemical substances.
The report has been published first at the magazine Nature (online). You can find it here.
More information: Munich School of BioEngineering (MSB): https://www.bioengineering.tum.de