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An electric-eel-inspired soft power source from stacked hydrogels


Progress towards the integration of technology into living organisms requires electrical power sources that are biocompatible, mechanically flexible, and able to harness the chemical energy available inside biological systems. Conventional batteries were not designed with these criteria in mind. The electric organ of the knifefish Electrophorus electricus (commonly known as the electric eel) is, however, an example of an electrical power source that operates within biological constraints while featuring power characteristics that include peak potential differences of 600 volts and currents of 1 ampere1,2. Here we introduce an electric-eel-inspired power concept that uses gradients of ions between miniature polyacrylamide hydrogel compartments bounded by a repeating sequence of cation- and anion-selective hydrogel membranes. The system uses a scalable stacking or folding geometry that generates 110 volts at open circuit or 27 milliwatts per square metre per gel cell upon simultaneous, self-registered mechanical contact activation of thousands of gel compartments in series while circumventing power dissipation before contact. Unlike typical batteries, these systems are soft, flexible, transparent, and potentially biocompatible. These characteristics suggest that artificial electric organs could be used to power next-generation implant materials such as pacemakers, implantable sensors, or prosthetic devices in hybrids of living and non-living systems3,4,5,6.

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Figure 1: Morphology and mechanism of action of the eel’s electric organ and the artificial electric organ.
Figure 2: Fluidic and printed artificial electric organs.
Figure 3: Artificial electric organ morphologies based on thin hydrogel films.


  1. 1

    Bennett, M. V. L. in Fish Physiology Vol. 5 (eds Hoar, W. S. & Randall, D. J. ) 347–491 (Academic Press, 1971)

  2. 2

    Gotter, A. L., Kaetzel, M. A. & Dedman, J. R. Electrophorus electricus as a model system for the study of membrane excitability. Comp. Biochem. Physiol. A Mol. Integr. Physiol. 119, 225–241 (1998)

    CAS  Article  Google Scholar 

  3. 3

    Xu, J., Sigworth, F. J. & LaVan, D. A. Synthetic protocells to mimic and test cell function. Adv. Mater. 22, 120–127 (2010)

    CAS  Article  Google Scholar 

  4. 4

    Sun, H., Fu, X., Xie, S., Jiang, Y. & Peng, H. Electrochemical capacitors with high output voltages that mimic electric eels. Adv. Mater. 28, 2070–2076 (2016)

    CAS  Article  Google Scholar 

  5. 5

    Kim, D.-H. et al. Epidermal electronics. Science 333, 838–843 (2011)

    ADS  CAS  Article  Google Scholar 

  6. 6

    Whitesides, G. M. Assumptions: taking chemistry in new directions. Angew. Chem. Int. Ed. 43, 3632–3641 (2004)

    CAS  Article  Google Scholar 

  7. 7

    Gallant, J. R. et al. Nonhuman genetics. Genomic basis for the convergent evolution of electric organs. Science 344, 1522–1525 (2014)

    ADS  CAS  Article  Google Scholar 

  8. 8

    Catania, K. C. Leaping eels electrify threats, supporting Humboldt’s account of a battle with horses. Proc. Natl Acad. Sci. USA 113, 6979–6984 (2016)

    CAS  Article  Google Scholar 

  9. 9

    Xu, J. & Lavan, D. A. Designing artificial cells to harness the biological ion concentration gradient. Nat. Nanotechnol. 3, 666–670 (2008)

    ADS  CAS  Article  Google Scholar 

  10. 10

    Brown, M. V. The electric discharge of the electric eel. Electr. Eng. 69, 145–147 (1950)

    Article  Google Scholar 

  11. 11

    Nachmansohn, D., Cox, R. T., Coates, C. W. & Machado, A. L. Action potential and enzyme activity in the electric organ of Electrophorus electricus (Linnaeus): I. Choline esterase and respiration. J. Neurophysiol. 5, 499–515 (1942)

    CAS  Article  Google Scholar 

  12. 12

    Keynes, R. D. & Martins-Ferreira, H. Membrane potentials in the electroplates of the electric eel. J. Physiol. 119, 315–351 (1953)

    CAS  Article  Google Scholar 

  13. 13

    Cox, R. T., Coates, C. W. & Brown, M. V. Electrical characteristics of electric tissue. Ann. NY Acad. Sci. 47, 487–500 (1946)

    ADS  CAS  Article  Google Scholar 

  14. 14

    Pattle, R. E. Production of electric power by mixing fresh and salt water in the hydroelectric pile. Nature 174, 660–660 (1954)

    ADS  CAS  Article  Google Scholar 

  15. 15

    Zeng, S., Li, B., Su, X., Qin, J. & Lin, B. Microvalve-actuated precise control of individual droplets in microfluidic devices. Lab Chip 9, 1340–1343 (2009)

    CAS  Article  Google Scholar 

  16. 16

    Bardin, D. et al. High-speed, clinical-scale microfluidic generation of stable phase-change droplets for gas embolotherapy. Lab Chip 11, 3990–3998 (2011)

    CAS  Article  Google Scholar 

  17. 17

    Young, C., Rozario, K., Serra, C., Poole-Warren, L. & Martens, P. Poly(vinyl alcohol)-heparin biosynthetic microspheres produced by microfluidics and ultraviolet photopolymerisation. Biomicrofluidics 7, 44109 (2013)

    Article  Google Scholar 

  18. 18

    Gumuscu, B. et al. Desalination by electrodialysis using a stack of patterned ion-selective hydrogels on a microfluidic device. Adv. Funct. Mater. 26, 8685–8693 (2016)

    CAS  Article  Google Scholar 

  19. 19

    Miura, K. Method of Packaging and Deployment of Large Membranes in Space. Report No. 618 (Institute of Space and Astronautical Science, 1985)

  20. 20

    Shenkel, S. & Sigworth, F. J. Patch recordings from the electrocytes of Electrophorus electricus. Na currents and PNa/PK variability. J. Gen. Physiol. 97, 1013–1041 (1991)

    CAS  Article  Google Scholar 

  21. 21

    Ide, T., Takeuchi, Y. & Yanagida, T. Development of an experimental apparatus for simultaneous observation of optical and electrical signals from single ion channels. Single Mol. 3, 33–42 (2002)

    ADS  CAS  Article  Google Scholar 

  22. 22

    Feng, J. et al. Single-layer MoS2 nanopores as nanopower generators. Nature 536, 197–200 (2016)

    ADS  CAS  Article  Google Scholar 

  23. 23

    Lingley, A. R. et al. A single-pixel wireless contact lens display. J. Micromech. Microeng. 21, 125014 (2011)

    ADS  Article  Google Scholar 

  24. 24

    Mansouri, K., Medeiros, F. A., Tafreshi, A. & Weinreb, R. N. Continuous 24-hour monitoring of intraocular pressure patterns with a contact lens sensor: safety, tolerability, and reproducibility in patients with glaucoma. Arch. Ophthalmol. 130, 1534–1539 (2012)

    Article  Google Scholar 

  25. 25

    Lai, Y.-C. et al. Electric eel-skin-inspired mechanically durable and super-stretchable nanogenerator for deformable power source and fully autonomous conformable electronic-skin applications. Adv. Mater. 28, 10024–10032 (2016)

    CAS  Article  Google Scholar 

  26. 26

    Ilievski, F., Mazzeo, A. D., Shepherd, R. F., Chen, X. & Whitesides, G. M. Soft robotics for chemists. Angew. Chem. Int. Ed. 50, 1890–1895 (2011)

    CAS  Article  Google Scholar 

  27. 27

    Chandrakasan, A. P., Verma, N. & Daly, D. C. Ultralow-power electronics for biomedical applications. Annu. Rev. Biomed. Eng. 10, 247–274 (2008)

    CAS  Article  Google Scholar 

  28. 28

    Enger, C. C. & Simeone, F. A. Biologically energized cardiac pacemaker: in vivo experience with dogs. Nature 218, 180–181 (1968)

    ADS  CAS  Article  Google Scholar 

  29. 29

    Chin, S. Y. et al. Additive manufacturing of hydrogel-based materials for next-generation implantable medical devices. Sci. Robot. 2, eaah6451 (2017)

    Article  Google Scholar 

  30. 30

    Cox, R. T., Rosenblith, W. A., Cutler, J. A., Mathews, R. S. & Coates, C. W. A comparison of some electrical and anatomical characteristics of the electric eel, Electrophorus electricus. Zoologica 25, 553–562 (1940)

    Google Scholar 

  31. 31

    Schoffeniels, E. Ion movements studied with single isolated electroplax. Ann. NY Acad. Sci. 81, 285–306 (1959)

    ADS  CAS  Article  Google Scholar 

  32. 32

    Altamirano, M. & Coates, C. W. Effect of potassium on electroplax of Electrophorus electricus. J. Cell. Comp. Physiol. 49, 69–101 (1957)

    CAS  Article  Google Scholar 

  33. 33

    Nakamura, Y., Nakajima, S. & Grundfest, H. Analysis of spike electrogenesis and depolarizing K inactivation in electroplaques of Electrophorus electricus, L. J. Gen. Physiol. 49, 321–349 (1965)

    Google Scholar 

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We are grateful to B. Rothen-Rutishauser and A. Petri-Fink at the Adolphe Merkle Institute for the use of their 3DDiscovery printer. F. Bircher’s iPrint institute at the Haute École d’Ingénierie et d’Architecture Fribourg, particularly F. Bourguet and M. Soutrenon, donated time towards adapting a printer for our use and helped us to understand the intricacies of microvalve printing systems. Laser cutting was performed at Fablab Fribourg. U. Steiner’s group, in particular P. Sutton and M. Fischer, provided instrumentation and advice related to impedance measurements. Research reported in this publication was supported by the Air Force Office of Scientific Research (grant FA9550-12-1-0435 to M.M., J.Y., D.S. and M.S.) and the National Institute of General Medical Sciences of the National Institutes of Health under award T32GM008353, which funds the Cellular Biotechnology Training Program (T.B.H.S.). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Author information




T.B.H.S., A.G., J.Y. and M.M. conceived the project and designed the experiments. T.B.H.S. and A.G. performed all data collection. A.L. and M.S. provided the idea of Miura-ori folding. G.V. helped to define the parameters of the fluidic implementation. T.B.H.S. and D.S. conducted analysis of literature electrical datasets of Electrophorus. T.B.H.S., A.G. and M.M. wrote the manuscript.

Corresponding author

Correspondence to Michael Mayer.

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Competing interests

The authors declare no competing financial interests.

Additional information

Reviewer Information Nature thanks C. Bettinger, P. Calvert and A. Stokes for their contribution to the peer review of this work.

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Extended data figures and tables

Extended Data Figure 1 Charged monomers used in charge-selective ‘membrane’ gels.

a, 3-Sulfopropyl acrylate, a component of the cation-selective gel. b, (3-Acrylamidopropyl)trimethylammonium, a component of the anion-selective gel.

Extended Data Figure 2 Self-discharge of artificial electric organ over time after contact between all gels, with and without exposure to ambient air.

Curves were fit with a single exponential decay function (dotted curves); the half-time for each was 40 min. The artificial electric organ was assembled as described in Supplementary Information 3. Supplementary Video 1 shows a fluidic implementation of the artificial electric organ which positions gels into contact sequentially rather than simultaneously. Large-scale implementations of similar sequential positioning schemes may be prone to power loss from gradient depletion unless positioning could be accomplished rapidly.

Extended Data Figure 3 The artificial electric organ can be recharged.

Experimental details in Supplementary Information 3. a, Current versus time recordings of ten discharges of a single tetrameric gel cell at short circuit following recharging. Initial discharge shown in black; subsequent discharges in the following order: red, blue, magenta, green, navy, purple, plum, wine, olive. b, Bar graph of normalized integrals of discharge curves.

Extended Data Figure 4 Geometrical arrangement of the printed 45° Miura-ori gel cells.

Dotted lines of a single colour indicate gels forming a series. Different colours indicate parallel sequences. This fold geometry is scalable both in series for higher voltage output and in parallel for higher current. In contrast to the 80° Miura-ori fold, all gels are located on the same side of the substrate, facilitating fabrication by printing or other methods. (Supplementary Information 5).

Extended Data Figure 5 Internal resistance and power density of tetrameric gel cells as a function of thickness of low-salinity gel.

Internal resistance, black squares; power density, red circles. The thicknesses of all other gels were held constant at 1 mm.

Extended Data Figure 6 Equivalent circuit of an artificial electric organ connected to a load resistance.

The elements within the dotted line represent the contribution of a single tetrameric gel cell; these can be added in series or in parallel. The impedance of the voltmeter that was used exceeded 10 GΩ; current through this pathway was assumed to be negligible.

Extended Data Table 1 Selectivity of membranes considered in this work
Extended Data Table 2 Electrical characteristics from fluidic assembly of gel cells in series and parallel
Extended Data Table 3 Absolute permeability values of membranes considered in this work

Related audio

Supplementary information

Supplementary Information

This file contains seven discussion sections and two supplementary tables. The contents are theoretical background, characterization, fabrication methods, and calculations related to the artificial electric organ presented in this work. (PDF 593 kb)

Fluidic artificial organ implementation

This video shows fluidic artificial organ implementation. (MP4 11160 kb)

Printer depositing gels for serpentine implementation.

This video shows printer depositing gels for serpentine implementation. (MP4 19167 kb)

Miura-ori folding of a gel-bearing substrate

This video shows Miura-ori folding of a gel-bearing substrate. (MP4 2015 kb)

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Schroeder, T., Guha, A., Lamoureux, A. et al. An electric-eel-inspired soft power source from stacked hydrogels. Nature 552, 214–218 (2017).

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