Monday, March 4, 2013

Article: In the news: extracting energy from the biologic battery in the inner-ear

A group of researchers consisting of Patrick Mercier (principal investigator of the Energy-Efficient Microsystems Group), Andrew Lysaght, Saurav Bandyopadhyay, Anantha Chandrakasan, and Konstantina Stankovic have discovered how to extract power from the biologic battery that occurs naturally within the inner-ear of mammals.  The results, featured in the journal Nature Biotechnology this week, show for the first time that it is not only possible to extract energy from the ear, but that it is also possible to use this energy to power useful electronic devices – in this case a miniaturized radio transmitter and sensor.

One of the main engineering challanges of building such a bioelectronics and energy harvesting system is that the extractable power from the inner-ear is extremely small – on the order of a few nanowatts.  By employing innovative near-zero-leakage power electronics, the researchers were able to boost the voltage of the biologic battery from approximately 80 mV to 1 V, which was then used to operated a 2.4 GHz radio transmitter.  The resulting chip design, implemented in a 180nm CMOS technology, employed an extremely duty-cycled energy-buffering architecture, where the radio transmitted a single packet approximately once per minute.


More detailed information regarding chip implementation results, clinical experiments, and future directions can be found in the paper here.

Anatomy and physiology of the inner ear.
(a) Schematic of a mammalian ear including the external, middle and inner ear, which contains the cochlea and vestibular end organs. The endoelectronics chip is illustrated in one possible location, although the experiments were done with the chip located outside of the middle ear cavity. (b) Cross-section of a typical cochlear half-turn, showing the endolymphatic space (yellow) bordered by tight junctions (red), the stria vascularis (green) and hair cells (blue), which are contacted by primary auditory neurons (orange).

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