One of the factors that may improve the quality of the signal transmission between
a cochlear implant electrode carrier and the fibers of the auditory nerve is by reducing
the distance inbetween. To achieve this, an electrode carrier prototype with an integrated
thin wire (Ø100 µm) made of Nitinol, a shape memory alloy, is proposed. The wire acts
as an actuator that has been formed to adopt the spiral shape of a cochlea. In order
to activate the shape memory effect of the wire, it may be electrically heated.
A cochlear implant electrode carrier prototype was developed by integrating a Ø100
µm Nitinol wire behind the electrode. The first prototypes were developed by modifying
a Cochlear Nucleus Hybrid™ L24 (Cochlear Ltd., Sydney, Australia) electrode and replacing
the stiffener with the Nitinol wire. To enable electrical heating, copper wires were
crimped on both ends of the wire. A proof-of-concept was performed by inserting the
developed electrode array prototype into a temporal bone. After successful insertion
of the electrode carrier prototype, specimen preparation was performed and histological
evaluation was made.
According to the histological evaluation, an angular insertion depth of 360 ° was
achieved by the prototype. Furthermore, no indications of thermal damage to the soft
tissue structures were revealed. A perimodiolar position of the prototype could be
realized.
The histological evaluation from the first temporal bone experiment showed no intracochlear
damage and preservation of the basilar membrane. This finding motivates further research
on integrating a shape memory alloy to the electrode carrier. Through the shape memory
effect of the Nitinol wire, the electrode carrier can be formed to a specified geometry
allowing a perimodiolar positioning of the implant.
