Wireless charging comes to Implantable hearing aids

February 20, 2014 // By Julien Happich
At this year’s IEEE International Solid-State Circuits Conference, MIT researchers have presented a paper on fully implantable hearing aids that would not require any connection to an external apparatus for operation, hence remaining invisible.

In their paper “A Fully-Implantable Cochlear Implant SoC with Piezoelectric Middle-Ear Sensor and Energy-Efficient Stimulation in 0.18µm HVCMOS”, the researchers detail the design of a middle-ear implant that converts the vibrations of ossicles in the middle-ear into electric signals fed to the cochlear (a small spiral chamber in the inner ear) through micro-electrodes.

Demonstrated with measurements from human cadaveric temporal bones, the solution relies on a system-on-chip specifically designed to interface to a piezoelectric sensor, itself mounted at the umbo of the malleus within the middle ear, explains the paper. The IC also features a highly-reconfigurable digital sound processor that supports system power scalability through audio spectral channel selectivity. It also integrates neural stimulation via eight commercially available micro-electrodes.

Figure 1: A block diagram of the fully implantable cochlear implant SoC. Click image to enlarge.

First, a piezoelectric sensor frontend (PZFE) conditions the signal from the sensor (the sound-induced motion of the umbo), the signal is digitized by a low-power SAR ADC before a reconfigurable sound processor implements continuous interleaved sampling (CIS).