Description

* The primary objective of the project is to optimize the current thin-film stimulation electrode (TFSE) by replacing gold with platinum or a platinum/iridium compound. This material is commonly used by manufacturers in the field for standard stimulation electrodes, notably by Cochlear, owing to its highly suitable electrochemical properties. This material substitution will require adaptation of the current microfabrication process. The PhD candidate will fabricate TFSEs using a photosensitive polymer exhibiting excellent fracture resistance.
Regarding the electrode/tissue interface, the possibility of applying coatings onto the platinum stimulation electrodes will be investigated in order to reduce electrical impedance and increase charge injection capacity. Electrochemical characterization of the TFSE electrodes will be carried out in an artificial perilymph electrolyte. Chronopotentiometric measurements will be performed to determine the stimulation safety limit of 216 µC/cm²/phase (as defined by the AAMI standard), as well as the charge injection capacity and charge storage capacity. Finally, electrochemical impedance spectroscopy will be used to determine impedance values and phase variations before and after stimulation. These parameters will be optimized in order to approach the performance levels of standard stimulation electrode arrays.
A sensor will be integrated into the TFSE using a microfabrication procedure similar to that employed for the electrode itself. This sensor will enable real-time determination of the TFSE curvature state and provide feedback in the event of excessive contact forces or deformations exerted by the TFSE on the cochlear walls.
* The second objective will consist in performing insertion tests of active TFSEs using a synthetic 3D-printed cochlear model. This transparent model will enable video recording of the insertion procedure, as well as verification of electrode behavior, curvature variations, final positioning of the active TFSE, and sensor response. The results will be analyzed jointly with French Institute for Research in Computer Science and Automation (Defrost team, Inria Defrost Team) and the Institut de l’Audition (IdA Pasteur, Institut de l’Audition) for initial clinical validation studies.
* The third objective will be to directly connect the 22 stimulation channels of the TFSE, together with the actuator and the sensor, to the microprocessor through dedicated electrical feedthroughs. The interconnection between a thin-film device and rigid wired feedthroughs represent a major technological challenge. This connection will have to withstand environmental constraints including handling, surgery, traction, and bending, and will undergo several validation tests, notably tensile, flexural, and electrical leakage tests, in order to verify compliance with ISO/AAMI standards applicable to cochlear implants. Accelerated aging tests will also be conducted to evaluate robustness and identify failure modes such as delamination, cracking, or corrosion.

Skills required

The position is intended for a PhD candidate with a background in micro-mechatronics oriented toward implantable medical devices, possessing skills in microfabrication, electrochemical characterizations, and materials mechanics, and capable of evolving within an interdisciplinary academic–industrial environment. Sensitivity to regulatory constraints and technology transfer issues is also expected. The candidate must demonstrate a high level of autonomy.

Bibliography

Ahmad Itawi, Bacem Zribi, Prabhakar Sidambaram, Thanh Hang Tran, Guillaume Tourrel, Renato Torres, Sofiane Ghenna, Sébastien Grondel, Yann Nguyen, Cédric Plesse, Eric Cattan,
Steerable thin-film electrode array for cochlear implantation: design and development for future atraumatic insertion, Sensors and Actuators Reports, Volume 11, 2026, 100447, ISSN 2666-0539, https://doi.org/10.1016/j.snr.2026.100447.
(https://www.sciencedirect.com/science/article/pii/S2666053926000147)

Keywords

Cochlear Implant , Microfabrication, Polymer actuator, Modeling, Electrochemical characterizations