Dispersed Hydrogel Actuator for Modiolar Hugging Cochlear Implant Electrode Arrays

Objective: Cochlear implants are used in patients with profound deafness due to degeneration of hair cells inside the cochlea. As improvement for commercially available CIs with straight electrode arrays, it is desired that the electrode array hugs toward the nerve cells located at the central axis of the cochlea in order to reduce the stimulation distance. Therefore, we present a hydrogel-based actuated electrode shaft, which should bend itself when exposed to saline solution (simulating the intracochlear liquid perilymph). Methods: In vitro tests with the electrode arrays were performed in a cochlea model. Different quantities and grain sizes of the hydrogel-building polymer (polyacrylamide) were used to study the self-bending effect. Furthermore, material interfaces between the components were evaluated with scanning electron microscopy, fluorescence microscopy, and an adapted tape test according to DIN EN ISO 2409. Results: Self-bending of the electrode array was observed in the cochlea model and a maximum number of 3.1 turns was achieved. No delamination between the components could be observed. Conclusion: After insertion, we expect that the electrode shaft moves into a patient individual perimodiolar position without losing its functionality because of a delamination of the components. Significance: A modiolar hugging electrode design is presented, which may improve hearing restauration with cochlear implants due to an easier insertion technique and a patient individualized hugging to the modiolus.