Fully-Implantable Cochlear Device Enabled by Piezoelectric Sensor

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A fully-implantable, cochlear device has been developed for those affected by sensorineural hearing loss. Sensorineural hearing loss occurs when the cochlea cannot functionally convert the sound vibrations to electric stimulation of cochlear neurons.Current cochlear implants are secured to bone underneath the skin behind the external ear and transmit through internal cable to electrodes in the cochlea. The nanotechnology-enabled advance integrates various parts of a cochlear implant onto one chip that can be surgically implanted inside of the ear, spanning from the middle ear to the cochlea.

 

Termed a “system-on-chip” (SoC), the new cochlear implant prototype is 3.6mm x 3.6mm and consists of three main parts: the piezoelectric sensor, sound processing unit, and arbitrary waveform neural stimulator. The piezoelectric sensor, made of the nanomaterial Lead Zirconate Titanate (PZT), is located on the side of the chip that sits in the middle ear and receives acoustic stimuli (sound waves). The sensor is made of a piezoceramic material that detects pressure variations in the middle ear. Bending of the piezoceramic material in response to the pressure variations creates a change in voltage, and thus sound waves are converted into electric signals. Next, the sound processing unit configures the electric signal for the user and maximizes the energy-efficiency of the system. Finally, an electrode device that receives input from the environment and translates it to neural stimulation, called an arbitrary waveform neural stimulator, directly stimulates cochlear nerve fibers. As the nerve fibers are stimulated, signals are sent to the brain, allowing the user to interpret the original acoustic stimulus as sound. The combination of nanotechnology with electrical devices for a single SoC may prove significant for the development of smaller and smaller devices that can be seamlessly integrated into the human body[2].

 

References

  1. Yip M, Jin R, Nakajima HH, Stankovic KM, Chandrakasan AP. Fully-Implantable Cochlear Implant SoC With Piezoelectric Middle-Ear Sensor and Arbitrary Waveform Neural Stimulation. . [Internet]. 2014 . Available from: http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6910323
  2. Citekey <a href="http://dx.doi.org/10.5213%2Finj.2013.17.3.98" ref="reftype=other&amp;article-id=3797898&amp;issue-id=228443&amp;journal-id=1379&amp;FROM=Article%7CFront%20Matter&amp;TO=Content%20Provider%7CCrosslink%7CDOI&amp;rendering-type=normal" target="pmc_ext">10.5213/inj.2013.17.3.98</a> not found

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With piezoelectric sensors and arbitrary waveform neural stimulators enabling this technology, the nano-enabled cochlear implant has no external parts. The technology of the energy-optimal waveform allows this device to consume less power, removing the need for parts that would comprise the device’s battery and power supply. The stimulator component of the device uses a new, non-rectangular waveform that reduces power consumption by 15-35% but still properly stimulates the nerve fibers in the cochlea. In addition to the low power consumption of this device, the cochlear implant can be configured to the user by adjusting the power input and can be charged wirelessly, thus removing the need for a biologic battery or energy harvester[1].

 

References

  1. Hardesty L. Cochlear implants – with no exterior hardware. [Internet]. 2014 . Available from: http://www.nanowerk.com/news2/biotech/newsid=34327.php

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The fully-implantable cochlear implant improves sensorineural hearing devices and continues the trend of internalization of biotechnology. This nano-enabled cochlear implant can restore hearing to those who have hearing loss of more than 90 decibels. Unlike previous cochlear implants, which have external parts, it is virtually impossible to tell whether someone is using this device, sidestepping what can be for some implant recipients a source of social isolation. 

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The risks of this technology primarily involve the insertion and initial exposure of the device to the biological environment. For any implantable technology, it is important to consider the device's biocompatibility, structural design, power management, and wireless communication processes[1].  Currently, the PZT material used in this device is not biocompatible. However, research is being conducted to find an alternative material with comparable properties but increased biocompatibility. Surgical operation to insert the fully-implantable cochlear implant would be more extensive than that of the conventional cochlear implant, but risk during surgery would not increase significantly[2]. The waveforms, electronics, and sensor material involved in this device could potentially cause unforeseen physical or chemical changes in the complex and fragile auditory system. Because the device is made of a material that contains lead, proper disposal techniques would also need to be established in order to prevent potential environmental contamination.

 

References

  1. Citekey <a href="http://dx.doi.org/10.5213%2Finj.2013.17.3.98" ref="reftype=other&amp;article-id=3797898&amp;issue-id=228443&amp;journal-id=1379&amp;FROM=Article%7CFront%20Matter&amp;TO=Content%20Provider%7CCrosslink%7CDOI&amp;rendering-type=normal" target="pmc_ext">10.5213/inj.2013.17.3.98</a> not found
  2. Hardesty L. Cochlear implants – with no exterior hardware. [Internet]. 2014 . Available from: http://www.nanowerk.com/news2/biotech/newsid=34327.php

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