Power Hungry

Why do we want to extract electricity from blood glucose?

Many medical device technologies including pacemakers, neurostimulators, and prosthetic devices require electrical power to function throughout a person’s lifetime.¹ While standard battery technology continues to grow in capacity to power implanted devices, it faces a handful of inherent limitations: lithium ion batteries contain materials toxic to the body if leaked and have a finite lifespan unless they are implanted in a location that allows for wireless recharging.  However, inductive charging is limited in efficiency and is a time consuming process in biological tissues.¹¹  In addition, batteries that run out of power in devices like pacemakers often lead to costly and potentially dangerous replacement surgeries. 

A device that extracts electricity from blood glucose is a renewable solution that stands to eliminate all of these traditional grievances. Sufficient renewable power harvested from the body could remove battery life as a limiting factor in device lifespan and reduce overall cost by eliminating the need for replacement surgeries or frequent recharging. Given the glucose-consuming nature of the device, it may also be possible to perform blood glucose regulation for diabetics.

How can we extract electricity?

Membranes allow for some substances to pass through while preventing others.  This technology has advanced in recent years to the point where electricity can be extracted from glucose through the use of a fuel cell. A fuel cell is a device that functions similarly to a battery, with one of the key differences being it requires constant flow - reactants must enter the fuel cell, and waste products must exit for the generation of electricity to be constant. 

The ‘electricity generating’ part of the fuel cell is known as the membrane electrode assembly (MEA). MEAs are typically a sandwich of specific layers of material, each with physical and chemical properties that work together to facilitate a series of reactions that end with free electrons as a product. Our MEA is composed of two layers of catalyst with an alkaline exchange membrane (AEM) between them. The two catalysts separately make up the anode and cathode of the MEA, and each use their chemical properties to initiate separate reactions:

With this AEM technology, we’re working on developing a fuel cell that generates electricity from glucose. Such a lightweight, high capacity, electric power source that is easily recharged and wearable would have many benefits for powering implanted medical devices or prosthetic hands. 

We do this with abiotic catalysts that facilitate reactions on either end of an AEM. Traditionally, enzymes are used in glucose consuming fuel cells to facilitate the electricity generating reactions, but they are less effective for long term use due to the relatively short lifespans of the biological proteins.^2,3,4,5 The reactions, which occur separately at the anode and cathode each create products that are needed by the other. The cathode creates hydroxide ions that must travel through the semipermeable AEM to the anode, while the anode ‘creates’ electrons that cannot travel through the AEM and must go towards the cathode through an external circuit. The electrical potential that is created as a result between the anode and cathode is what is used to drive circuitry outside of the fuel cell. Catalysts used for this purpose in the past vary in specifics but are typically based around some type of platinum alloy.^6,7,8 The overall reaction consumes glucose and oxygen, both of which are readily bioavailable within animals.⁹

Our results have shown so far that much more work is needed! We have produced promising results that imply our fuel cell can generate electricity from glucose for a long period of time, but we must continue working to both:

• Improve the power density of the fuel cell. There is limited space within the body for implanted devices, so a fuel cell that runs off of blood glucose would need to generate a lot of power in a relatively small space! The fuel cell has currently been able to produce a maximum power density of 10.65 µW/cm2 in a solution with 10x the physiological level of glucose. The estimated power output needed to power a device like a pacemaker with a 1.6 Ampere-hour charge and a 13.2 year lifespan is ~34.59 µW.¹⁰

• Improve the biocompatibility of the fuel cell. The fuel cell will need to interface with blood, a mostly non-Newtonian and extremely complicated fluid in order to function within the body. It is important to show how the fuel cell interacts with blood, as right now it is generating electricity off of glucose in lab-created solutions. Generally, devices implanted into the bloodstream come with a high risk of the creation of thrombosis, so it is a task that must be approached with great caution. There have been early efforts, but testing for the biocompatibility of similar devices has limited precedent.^2,3,4

References

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1. Jiang, Dongjie, Bojing Shi, Han Ouyang, Yubo Fan, Zhong Lin Wang, Zhan-Ming Chen, and Zhou Li. “A 25-year bibliometric study of implantable energy harvesters and self-powered implantable medical electronics researches.” Materials Today Energy 16 (2020): 100386. https://doi.org/10.1016/j.mtener.2020.100386
2. A. Dector, R.A. Escalona-Villalpando, D. Dector, V. Vallejo-Becerra, A.U. Chávez-Ramírez, L.G. Arriaga, J. Ledesma-García, Perspective use of direct human blood as an energy source in air-breathing hybrid microfluidic fuel cells, Journal of Power Sources, Volume 288, 2015, Pages 70-75, ISSN 0378-7753, https://doi.org/10.1016/j.jpowsour.2015.04.089.
3. Dahye Lee, Sung Hee Jeong, Seunghyeon Yun, Sunhyo Kim, Jaehoon Sung, Jungmin Seo, Suyeon Son, Ji Tae Kim, Lina Susanti, Youngseok Jeong, Sanghyun Park, Kangmoon Seo, Sung June Kim, Taek Dong Chung, Totally implantable enzymatic biofuel cell and brain stimulator operating in bird through wireless communication, Biosensors and Bioelectronics, Volume 171, 2021, 112746, ISSN 0956-5663, https://doi.org/10.1016/j.bios.2020.112746.
4. Pankratov, D., Ohlsson, L., Gudmundsson, P., Halak, S., Ljunggren, L., Blum, Z., & Shleev, S. (2016). Ex vivo electric power generation in human blood using an enzymatic fuel cell in a vein replica. RSC Advances, 6(74), 70215-70220. doi:10.1039/c6ra17122b
5. Xiaoju Wang, Magnus Falk, Roberto Ortiz, Hirotoshi Matsumura, Johan Bobacka, Roland Ludwig, Mikael Bergelin, Lo Gorton, Sergey Shleev, Mediatorless sugar/oxygen enzymatic fuel cells based on gold nanoparticle-modified electrodes, Biosensors and Bioelectronics, Volume 31, Issue 1, 2012, Pages 219-225, ISSN 0956-5663, https://doi.org/10.1016/j.bios.2011.10.020.
6. S. Kerzenmacher, J. Ducrée, R. Zengerle, F. von Stetten, An abiotically catalyzed glucose fuel cell for powering medical implants: Reconstructed manufacturing protocol and analysis of performance, Journal of Power Sources, Volume 182, Issue 1, 2008, Pages 66-75, ISSN 0378-7753, https://doi.org/10.1016/j.jpowsour.2008.03.049.
7. Mohammad Zhiani, Saeid Barzi, Marzieh Gholamian, Ali Ahmadi, Synthesis and evaluation of Pt/rGO as the anode electrode in abiotic glucose fuel cell: Near to the human body physiological condition, International Journal of Hydrogen Energy, Volume 45, Issue 24, 2020, Pages 13496-13507, ISSN 0360-3199, https://doi.org/10.1016/j.ijhydene.2020.03.058.
8. D. Nnanyelugoh, A. Baingane, P. Miesse and G. Slaughter, "Glucose abiotic fuel cell," 2020 IEEE 15th International Conference on Nano/Micro Engineered and Molecular System (NEMS), San Diego, CA, USA, 2020, pp. 277-280, doi: 10.1109/NEMS50311.2020.9265559.
9. Santiago, Ó., Navarro, E., Raso, M. A., & Leo, T. J. (2016). Review of implantable and external abiotically catalysed glucose fuel cells and the differences between their membranes and catalysts. In Applied Energy (Vol. 179, pp. 497–522). https://doi.org/10.1016/j.apenergy.2016.06.13
10. ACCOLADE™ Pacing Systems. www.bostonscientific.com. (n.d.). https://www.bostonscientific.com/en-IN/products/pacemakers/accolade-pacing-systems1/battery-technology.html
11. M. J. Karimi, A. Schmid and C. Dehollain, "Wireless Power and Data Transmission for Implanted Devices via Inductive Links: A Systematic Review," in IEEE Sensors Journal, vol. 21, no. 6, pp. 7145-7161, 15 March15, 2021, doi: 10.1109/JSEN.2021.3049918.