Research Of MEMS-based Flexible Microelectrode Arrays For Cochlear Implant

Ear is an important organ that acquires the information from outside world.It is mainly constituted of the outer ear,the middle ear and the inner ear.Hearing loss may be resulted from any part of the auditory pathway.Since it has a great effect on all ages’groups,cochlear implant has been studied by scientists over the past years and more and more researches based on cochlear implant have been conducted.Cochlear implant is a device for implant.It has regained hearing to a certain extent to whose age between children with congenital hearing loss and hearing loss in the middle-aged and elderly patients.Cochlea is an important part of inner ear,which transfers acoustic signals into the electrical signals which are consequently preceded by brain.The main reason for the severe hearing loss is that the transformation is destroyed.The cochlear implant is proposed to exploit the frequency-to-place mapping in the cochlea by stimulating the auditory nerve electrically.In this study,the MEMS-based flexible microelectrode arrays for cochlear implant is proposed.The study mainly includes three parts.(1)The flexible microelectrode for cochlear implant is developed.The structure of microelectrode is designed based on the structure of the inner ear.In order to reduce the effect of spreading current,the structure for reducing signal crosstalk between the microelectrode is proposed.(2)The property for flexible microelectrode is tested and the surface of microelectrode is modified.An electrochemical method for the deposition of Ag/Ag Cl is proposed to modify the microelectrode arrays.The experimental results show that the fabricated Ag/Ag Cl microelectrode exhibits higher charge storage capacity than the unmodified one and the impedance of the Ag/Ag Cl modified microelectrode at 0.1 Hz is 7447?,which decreases with two orders of magnitude compared to the unmodified one.(3)Accelerated-lifetime soaking test are conducted to study the performance of device.After 6 months soaking test in the 0.9%Na Cl solution at 97℃,the average charge storage capacity decreased from10.34 m C/cm~2 to 2.44m C/cm~2 while the corresponding impedance at 1KHz increased from 3.66 kΩto 5.76 kΩ.The test results show that there was a little change in the electrochemical characteristics of the microelectrode.All these experimental results show that the lifetime of the device at 37℃is more than 32 years.