Endocochlear potential (EP) is a battery-like electrochemical gradient found in and actively maintained by the inner ear1,2. Here we demonstrate that the mammalian EP can be used as a power source for electronic devices. We achieved this by designing an anatomically sized, ultra-low quiescent-power energy harvester chip integrated with a wireless sensor capable of monitoring the EP itself. Although other forms of in vivo energy harvesting have been described in lower organisms3,4,5, and thermoelectric6, piezoelectric7 and biofuel8,9 devices are promising for mammalian applications, there have been few, if any, in vivo demonstrations in the vicinity of the ear, eye and brain. In this work, the chip extracted a minimum of 1.12 nW from the EP of a guinea pig for up to 5 h, enabling a 2.4 GHz radio to transmit measurement of the EP every 40–360 s. With future optimization of electrode design, we envision using the biologic battery in the inner ear to power chemical and molecular sensors, or drug-delivery actuators for diagnosis and therapy of hearing loss and other disorders.
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We acknowledge support from the C2S2 Focus Center and the Interconnect Focus Center, two of six research centers funded under the Focus Center Research Program (FCRP), a Semiconductor Research Corporation entity (A.P.C., P.P.M., S.B.), and from US National Institutes of Health grants K08 DC010419 (K.M.S.) and T32 DC00038 (A.C.L.) and the Bertarelli Foundation (K.M.S.). We thank J.J. Guinan Jr. for experimental assistance and advice, and B. Zhu for preliminary studies.
The authors declare no competing financial interests.
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Mercier, P., Lysaght, A., Bandyopadhyay, S. et al. Energy extraction from the biologic battery in the inner ear. Nat Biotechnol 30, 1240–1243 (2012). https://doi.org/10.1038/nbt.2394
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