Neural probes with integrated vertical organic electrochemical transistors (vOECTs)

Understanding the working mechanisms in the human brain is a key factor for development of medical implants for treating various diseases. For monitoring brain activity, neural probes are used to record signals from single to multiple neurons. The challenge here is to record these very small signals in the ?V range with a high signal-to-noise ratio over a long period, in particular for chronically implanted microelectrodes. At IMSAS, we developed free-floating neural probes for chronic in-vivo implantation, see e.g. https://doi.org/10.3390/mi9030131. With these probes we were able to record brain signals over a period of 3 months. However, we observed a degradation of the signal quality over time due to the foreign body response and tissue encapsulation of the probes.

Organic electrochemical transistors (OECTs) offer the possibility to transduce directly ionic to electric signals with a high amplification, in particular for vertical transistor channels, see e.g. https://doi.org/10.1002/aelm.202300673. This property is ideal for the application in biosensors, where ions are present at the transistor channel interface. In this project, we are developing vertical OECTs to record brain activity with a high signal-to-noise ratio. By integrating vertical OECTs on the thin silicon-based needle probes we will be able to amplify the tiny brain signals of neurons directly at the source, where they are generated. Compared to passive microelectrodes, we will be also able to detect ion fluctuations in the brain, which will allow us to record brain activity with more information.