The cochlear implant (CI) is the most successful neural prosthesis worldwide. Thanks to direct stimulation of the auditory nerve, it enables more than half a million people worldwide to hear, even though those affected were born deaf or deafened. In close collaboration, researchers from the Faculty of Medicine and the Faculty of Engineering at the University of Freiburg have developed a method to convert the stimulation electrodes of common CIs into electrochemical sensors. With the help of this novel sensor function, the functionality of cochlear implants could be monitored directly in the inner ear in the long term. The researchers published their results on December 9, 2021 in the journal Biosensors and Bioelectronics.