Current developments in sustainable and renewable energies focus mainly on bringing electrical energy to the masses. In these cases, technological development has not yet advanced to the point of making these energy sources efficient enough to be portable. This proves to be problematic for portable technologies, which require recharging or battery replacements. This is not an issue for the average smartphone user, but for those with medical implants and prosthetics, power loss could be fatal. Interestingly enough, the human body uses a series of electrochemical gradients in order to signal through the nervous system, to and produce ATP, the primary source of energy for cells (Mercier et al., 2012). Novel research shows that these gradients might also be a viable power sources.
Bioelectric potential is very similar to a battery, where the positive and negative ions are separated. In both cases, the flow of ions or electrons produces energy. In biological systems, the use of this concentration gradient is most commonly found in ATP synthase. The hydrogen ions that have been extracted by the electron transport chain are found in high concentration in the cristae of the mitochondrion, which then diffuse into the matrix of the mitochondrion through ATP synthase, which uses the potential energy to produce ATP. In the same way, an electron in a battery flows through a circuit, where it meets a component. The component will convert the electrical energy, such as in a light bulb, where the electricity causes electrons to jump to a high energy level. As the electron falls back to its original position, a photon is released.
In humans, the cochlea produces an electrochemical gradient of 70-100 mV, which is the largest electrochemical potential in the body (Hibino, 2010). This high concentration is required due to cochlea function, which translates vibrations of sound waves into the movement of the endolymph (Takeuchi, Ando & Kakigi, 2000). The endolymph moves and brushes hair cells, which causes the high concentration of potassium ions in the endolymph to pass through and depolarize the hair cells, initiating an action potential(Takeuchi, Ando & Kakigi, 2000). This excites the auditory nerve and sends auditory signals to the brain (Hibino, 2010). Since the cochlear gradient is unchanged in genetic defects for hearing loss, and remains relatively unaffected by age and trauma, it is an ideal candidate as an energy source for cochlear implants and hearing aids (Lang, Shulte & Schmeidt, 2010). In an in vivo study, the main method for acquiring energy was to place electrodes at points within the potassium ion pathway of the cochlea of a guinea pig, where potassium could provide energy, and then be returned to the cochlea (Mercier et al., 2012). This provided the voltage necessary for the power-testing component to function.
Although this novel power source is in its early stages, the potential for it is great. The use of bioelectric potential is not only sustainable; it is an easily accessible, portable energy (Mercier et al., 2012). The benefits of this power are in high demand within the medical technology market, and will improve the quality of life of disabled individuals.
Works Cited:
Hibino, H. et al., 2010. How is the highly positive endocochlear potential formed? The specific architecture of the stria vascularis and the roles of the ion-transport apparatus. Pflügers Archiv : European journal of physiology, 459(4), pp.521–33. Available at: http://www.ncbi.nlm.nih.gov/pubmed/20012478 [Accessed February 1, 2013].
Lang, H., Schulte, B. & Schmiedt, R., 2002. Endocochlear potentials and compound action potential recovery: functions in the C57BL/6J mouse. Hearing Research, 172(1-2), pp.118–126. Available at: http://dx.doi.org/10.1016/S0378-5955(02)00552-X [Accessed February 1, 2013].
Mercier, P.P. et al., 2012. Energy extraction from the biologic battery in the inner ear. Nature biotechnology, 30(12), pp.1240–3. Available at: http://dx.doi.org/10.1038/nbt.2394 [Accessed January 31, 2013].
Takeuchi, S., Ando, M. & Kakigi, A., 2000. Mechanism generating endocochlear potential: role played by intermediate cells in stria vascularis. Biophysical journal, 79(5), pp.2572–82. Available at: http://dx.doi.org/10.1016/S0006-3495(00)76497-6 [Accessed February 1, 2013].