Optogenetic OLED-on-CMOS Stimulators for Neurosensory Therapies
Researchers from the Fraunhofer IPMS and the Max Planck Institute NAT have researched optical stimulators for future cochlear implants as part of the "NeurOpto" project (funded by the Fraunhofer-Max-Planck Cooperation Program: 601001). They will present tiny OLED-on-silicon-based probes for the first time at W3+ 2024 in Jena, on September 25 and 26, 2024, at booth No. C12.
What is optogenetics?
Optogenetics is a technique that uses light to control genetically modified cells in living tissues. By introducing light-sensitive proteins into cells, their activity can be precisely turned on and off with light pulses. This technique is commonly used in neuroscience to study the functions of nerve cells and to activate or inhibit specific neuronal populations. Small and locally selective light sources are needed now to deliver light precisely to stimulate tiny cells.
Dr. Uwe Vogel, Head of Microdisplays and Sensors business unit at Fraunhofer IPMS, explains: "With OLED-on-silicon technology, we can bring tiny, locally controllable light pixels onto a chip. This chip can be flexibly designed to reach the desired locations even in curved structures like the cochlea. This allows light to be used precisely where electrical stimulation alone is insufficient."
Prof. Tobias Moser of the MPI-NAT adds: "The development of optical cochlear implants promises better hearing for the severely hearing impaired. MPI-NAT and University Medical Center Göttingen (UMG) are working closely with partners such as Fraunhofer IPMS on the technological solutions required for this. Intelligent implantable stimulators based on optical stimulation could also be used for other medical therapies such as laryngeal pacemakers, cardiac pacemakers, pain relieve, retinal implants, or deep brain stimulation."
How does optical cell stimulation work?
Current electric cochlear implants (eCIs) restore speech comprehension in quiet environments for most of the approximately 1 million users worldwide. However, speech recognition in background noise and enjoyment of music are often severely limited. The reason for this is the inadequate frequency resolution of electrical sound coding: each electrode contact also stimulates more distant nerve cells that code different frequencies due to the broad current spread. Since light can be controlled much more precisely, an optical cochlear implant (oCI) could overcome this problem. The number of independent frequency bands could be increased by spatially targeted optical stimulation of light-sensitive auditory nerve cells. This would be possible through dozens of microscale light emitters along the frequency axis of the cochlea, ideally individually controllable. The UMG/MPI-NAT has been collaborating with academic and industrial partners on the development of oCI and gene therapy for many years. The current collaboration with Fraunhofer IPMS focuses on the evaluation of OLED technology for use in oCIs.
Fraunhofer IPMS has used its experience in OLED-on-silicon technology for microdisplays to bring CMOS-integrated light sources of the highest pixel density and brightness, as well as the lowest power consumption, to a pixelated OLED microsensor that can individually control spatially distributed light channels that can be assigned to corresponding audio frequencies in the cochlea via a serial interface.
Where was the challenge in developing the technology?
Although Fraunhofer IPMS has already introduced unique features for microdisplays with its OLED-on-silicon technology, which are also important for optogenetics, there are still some challenges: The required brightness and level of integration have been successfully demonstrated during the project. However, flexibility and biocompatibility are not yet verified. The silicon microtechnology used has shown that these properties are generally achievable. With further research and development effort, they appear to be feasible here as well.
When will the technology be market-ready?
The project has laid the first foundations for the use of OLED-on-silicon technology in optogenetics. The results are promising. The scientists will continue to work on this technology and remain open to other areas of application.
Source: Fraunhofer IPMS
www.ipms.fraunhofer.de/en
Caption 1: OLED-on-Silicon Technology for Optogenetics.
Caption 2: Electrical vs. Optical Cochlea Stimulation - Above: The current from each of the 12 electrode contacts of a conventional electrical cochlear implant spreads widely. Below: The light from nearly one hundred independent micro-light-emitting diodes of an optical cochlear implant can be projected onto a small area.