Optogenetic OLED-on-CMOS stimulators for neurosensory therapies

Funded by the Fraunhofer-Max-Planck Cooperation Program, the team will present their innovative OLED-on-silicon-based probes for the first time at W3+ 2024, held in Jena on 25th and 26th September 2024, at booth C12.

Optogenetics is a technique that utilises light to control genetically modified cells within living tissues. By introducing light-sensitive proteins into the cells, their activity can be precisely activated or inhibited using light pulses. This method is widely used in neuroscience to explore the functions of nerve cells and to manipulate specific neuronal populations. To achieve precise cell stimulation, compact, locally selective light sources are crucial, a challenge the researchers have addressed with their new technology.

Current electrical cochlear implants (eCIs) restore speech comprehension in quiet environments for most of the 1 million users worldwide. However, these devices often struggle with speech recognition in noisy environments and are limited in music appreciation due to poor frequency resolution. This is because electrical stimulation spreads broadly, activating not only target nerve cells but also distant ones that correspond to different frequencies.

Optical cochlear implants (oCIs) offer a potential solution to this issue. Light can be controlled with far greater precision than electrical currents, allowing for more accurate stimulation of auditory nerve cells (SGNs). By incorporating dozens of microscale light emitters along the cochlea's frequency axis, each tuned to specific auditory frequencies, oCIs could offer more refined sound processing and improved hearing performance.

Professor Tobias Moser from MPI-NAT highlighted the potential of optical stimulation: “The development of optical cochlear implants promises significantly improved hearing for the severely hearing impaired. MPI-NAT and University Medical Center Göttingen (UMG) are collaborating with partners such as Fraunhofer IPMS to develop the required technological solutions. In the future, optical stimulation could be applied in other medical devices, including laryngeal pacemakers, cardiac pacemakers, pain relief systems, retinal implants, and deep brain stimulation."

The collaboration between Fraunhofer IPMS and MPI-NAT has focused on leveraging OLED-on-silicon technology for use in oCIs. Fraunhofer IPMS has applied its expertise from the microdisplay sector to develop CMOS-integrated light sources with high pixel density and brightness, coupled with low power consumption. This has enabled the creation of pixelated OLED microsensors that can individually control light emissions along the cochlea, corresponding to specific audio frequencies.

Despite these advancements, challenges remain. While the necessary brightness and integration have been successfully demonstrated, issues surrounding flexibility and biocompatibility are still being addressed. The silicon-based microtechnology used in this project has shown promising results, suggesting that these hurdles are achievable with continued research and development.

Although the project has established a strong foundation for applying OLED-on-silicon technology in optogenetics, there is still work to be done before it becomes commercially available. The team is optimistic about the potential of this technology and remains open to exploring additional applications beyond cochlear implants.

As Professor Moser concluded: “The results are highly promising, and we will continue to refine this technology for use in various medical therapies. We are confident that with further development, optical stimulation could become a transformative tool for medical implants."