Energy extraction from the biologic battery in the inner ear

The energy of the electrochemical potential in the guinea pig cochlea is harvested and used to power a wireless transmitter. Endocochlear potential (EP) is a battery-like electrochemical gradient found in and actively maintained by the inner ear 1 , 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 organisms 3 , 4 , 5 , and thermoelectric 6 , piezoelectric 7 and biofuel 8 , 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.