Sweat-activated biocompatible batteries for epidermal electronic and microfluidic systems


Recent advances in materials, mechanics and design have led to the development of ultrathin, lightweight electronic devices that can conformally interface with human skin. With few exceptions, these devices rely on electrical power to support sensing, wireless communication and signal conditioning. Unfortunately, most sources of such power consist of batteries constructed using hazardous materials, often with form factors that frustrate incorporation into skin-like, or epidermal, electronic devices. Here we report a biocompatible, sweat-activated battery technology that can be embedded within a soft, microfluidic platform. The battery can be used in a detachable electronic module that contains wireless communication and power management systems, and is capable of continuous on-skin recording of physiological signals. To illustrate the practical utility of our approach, we show using human trials that the sweat-activated batteries can operate hybrid microfluidic/microelectronic systems that simultaneously monitor heart rate, sweat chloride and sweat pH.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Working principles and characteristics of an SAC.
Fig. 2: Discharge properties and EIS studies of SAC.
Fig. 3: Power management circuit and its characteristics.
Fig. 4: SAC-powered, skin-interfaced hybrid microfluidic–microelectronic system.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding authors upon reasonable request.

Code availability

Custom-developed firmware for the electronic module and LabView data acquisition software for hardware characterization are available from the corresponding authors upon reasonable request.


  1. 1.

    Ray, T. R. et al. Bio-integrated wearable systems: a comprehensive review. Chem. Rev. 119, 5461–5533 (2019).

    Google Scholar 

  2. 2.

    Song, Y., Min, J. & Gao, W. Wearable and implantable electronics: moving toward precision therapy. ACS Nano 13, 12280–12286 (2019).

    Google Scholar 

  3. 3.

    Bariya, M., Nyein, H. Y. Y. & Javey, A. Wearable sweat sensors. Nat. Electron. 1, 160 (2018).

    Google Scholar 

  4. 4.

    Choi, J. et al. Soft, skin-integrated multifunctional microfluidic systems for accurate colorimetric analysis of sweat biomarkers and temperature. ACS Sens. 4, 379–388 (2019).

    Google Scholar 

  5. 5.

    Caldara, M., Colleoni, C., Guido, E., Re, V. & Rosace, G. Optical monitoring of sweat pH by a textile fabric wearable sensor based on covalently bonded litmus-3-glycidoxypropyltrimethoxysilane coating. Sens. Actuators B 222, 213–220 (2016).

    Google Scholar 

  6. 6.

    Reeder, J. T. et al. Resettable skin interfaced microfluidic sweat collection devices with chemesthetic hydration feedback. Nat. Commun. 10, 5513 (2019).

    Google Scholar 

  7. 7.

    Yang, Y. et al. A laser-engraved wearable sensor for sensitive detection of uric acid and tyrosine in sweat. Nat. Biotechnol. 38, 217–224 (2020).

    Google Scholar 

  8. 8.

    Kim, J. et al. Simultaneous monitoring of sweat and interstitial fluid using a single wearable biosensor platform. Adv. Sci. 5, 1800880 (2018).

    Google Scholar 

  9. 9.

    Khan, Y. et al. Organic multi-channel optoelectronic sensors for wearable health monitoring. IEEE Access 7, 128114–128124 (2019).

    Google Scholar 

  10. 10.

    Kafi, M. A., Paul, A., Vilouras, A., Hosseini, E. S. & Dahiya, R. S. Chitosan-graphene oxide based ultra-thin and flexible sensor for diabetic wound monitoring. IEEE Sens. J. 13, 6794–6801 (2019).

  11. 11.

    Lee, K. et al. Mechano-acoustic sensing of physiological processes and body motions via a soft wireless device placed at the suprasternal notch. Nat. Biomed. Eng. 4, 148–158 (2020).

    Google Scholar 

  12. 12.

    Imani, S. et al. A wearable chemical–electrophysiological hybrid biosensing system for real-time health and fitness monitoring. Nat. Commun. 7, 11650 (2016).

    Google Scholar 

  13. 13.

    Yin, L. et al. Highly stable battery pack via insulated, reinforced, buckling-enabled interconnect array. Small 14, 1800938 (2018).

    Google Scholar 

  14. 14.

    Liu, R. et al. Shape memory polymers for body motion energy harvesting and self‐powered mechanosensing. Adv. Mater. 30, 1705195 (2018).

    Google Scholar 

  15. 15.

    Mokhtari, F., Foroughi, J., Zheng, T., Cheng, Z. & Spinks, G. M. Triaxial braided piezo fiber energy harvesters for self-powered wearable technologies. J. Mater. Chem. A 7, 8245–8257 (2019).

    Google Scholar 

  16. 16.

    Bandodkar, A. J. Wearable biofuel cells: past, present and future. J. Electrochem. Soc. 164, H3007–H3014 (2017).

    Google Scholar 

  17. 17.

    Chen, X. et al. Stretchable and flexible buckypaper-based lactate biofuel cell for wearable electronics. Adv. Funct. Mater. 29, 1905785 (2019).

    Google Scholar 

  18. 18.

    Yu, Y. et al. Biofuel-powered soft electronic skin with multiplexed and wireless sensing for human-machine interfaces. Sci. Robot. 5, eaaz7946 (2020).

    Google Scholar 

  19. 19.

    Hu, X. et al. Nacre-inspired crystallization and elastic “brick-and-mortar” structure for a wearable perovskite solar module. Energy Environ. Sci. 12, 979–987 (2019).

    Google Scholar 

  20. 20.

    O’Connor, T. F. et al. Wearable organic solar cells with high cyclic bending stability: materials selection criteria. Sol. Energy Mater. Sol. Cells 144, 438–444 (2016).

    Google Scholar 

  21. 21.

    Li, C. et al. Flexible perovskite solar cell-driven photo-rechargeable lithium-ion capacitor for self-powered wearable strain sensors. Nano Energy 60, 247–256 (2019).

    Google Scholar 

  22. 22.

    Ostfeld, A. E., Gaikwad, A. M., Khan, Y. & Arias, A. C. High-performance flexible energy storage and harvesting system for wearable electronics. Sci. Rep. 6, 26122 (2016).

    Google Scholar 

  23. 23.

    Huang, X. et al. Epidermal radio frequency electronics for wireless power transfer. Microsyst. Nanoeng. 2, 16052 (2016).

    Google Scholar 

  24. 24.

    Bito, J., Hester, J. G. & Tentzeris, M. M. Ambient RF energy harvesting from a two-way talk radio for flexible wearable wireless sensor devices utilizing inkjet printing technologies. IEEE Trans. Microw. Theory Tech. 63, 4533–4543 (2015).

    Google Scholar 

  25. 25.

    Rose, D. P. et al. Adhesive RFID sensor patch for monitoring of sweat electrolytes. IEEE Trans. Biomed. 62, 1457–1465 (2015).

    Google Scholar 

  26. 26.

    Bandodkar, A. J. et al. Battery-free, skin-interfaced microfluidic/electronic systems for simultaneous electrochemical, colorimetric, and volumetric analysis of sweat. Sci. Adv. 5, eaav3294 (2019).

    Google Scholar 

  27. 27.

    Niu, S. et al. A wireless body area sensor network based on stretchable passive tags. Nat. Electron. 2, 361–368 (2019).

    Google Scholar 

  28. 28.

    Liu, W., Song, M. S., Kong, B. & Cui, Y. Flexible and stretchable energy storage: recent advances and future perspectives. Adv. Mater. 29, 1603436 (2017).

    Google Scholar 

  29. 29.

    Zhang, Y., Zhao, Y., Ren, J., Weng, W. & Peng, H. Advances in wearable fiber‐shaped lithium‐ion batteries. Adv. Mater. 28, 4524–4531 (2016).

    Google Scholar 

  30. 30.

    Liu, Q.-C. et al. A flexible and wearable lithium–oxygen battery with record energy density achieved by the interlaced architecture inspired by bamboo slips. Adv. Mater. 28, 8413–8418 (2016).

    Google Scholar 

  31. 31.

    Kumar, R. et al. All‐printed, stretchable Zn‐Ag2O rechargeable battery via hyperelastic binder for self‐powering wearable electronics. Adv. Energy Mater. 7, 1602096 (2017).

    Google Scholar 

  32. 32.

    Ji, D. et al. Atomically transition metals on self‐supported porous carbon flake arrays as binder‐free air cathode for wearable zinc−air batteries. Adv. Mater. 31, 1808267 (2019).

    Google Scholar 

  33. 33.

    Li, H. et al. An extremely safe and wearable solid-state zinc ion battery based on a hierarchical structured polymer electrolyte. Energy Environ. Sci. 11, 941–951 (2018).

    Google Scholar 

  34. 34.

    Berchmans, S. et al. An epidermal alkaline rechargeable Ag–Zn printable tattoo battery for wearable electronics. J. Mater. Chem. A 2, 15788–15795 (2014).

    Google Scholar 

  35. 35.

    Yang, Y. et al. Waterproof, ultrahigh areal‐capacitance, wearable supercapacitor fabrics. Adv. Mater. 29, 1606679 (2017).

    Google Scholar 

  36. 36.

    Rajendran, V., Mohan, A. M. V., Jayaraman, M. & Nakagawa, T. All-printed, interdigitated, freestanding serpentine interconnects based flexible solid state supercapacitor for self powered wearable electronics. Nano Energy 65, 104055 (2019).

    Google Scholar 

  37. 37.

    Lee, K. B. Urine-activated paper batteries for biosystems. J. Micromech. Microeng. 15, S210–S214 (2005).

    Google Scholar 

  38. 38.

    Koo, Y., Sankar, J. & Yun, Y. High performance magnesium anode in paper-based microfluidic battery, powering on-chip fluorescence assay. Biomicrofluidics 8, 054104 (2014).

    Google Scholar 

  39. 39.

    Ortega, L., Llorella, A., Esquivel, J. P. & Sabaté, N. Self-powered smart patch for sweat conductivity monitoring. Microsyst. Nanoeng. 5, 3 (2019).

    Google Scholar 

  40. 40.

    She, D., Tsang, M. & Allen, M. Biodegradable batteries with immobilized electrolyte for transient MEMS. Biomed. Microdevices 21, 17 (2019).

    Google Scholar 

  41. 41.

    Liu, G. et al. A wearable conductivity sensor for wireless real-time sweat monitoring. Sens. Actuators B 227, 35–42 (2016).

    Google Scholar 

  42. 42.

    Emrich, H. M. et al. Sweat composition in relation to rate of sweating in patients with cystic fibrosis of the pancreas. Pediatr. Res. 2, 464–478 (1968).

    Google Scholar 

  43. 43.

    Buono, M. J., Ball, K. D. & Kolkhorst, F. W. Sodium ion concentration vs. sweat rate relationship in humans. J. Appl. Physiol. 103, 990–994 (2007).

    Google Scholar 

  44. 44.

    Bandodkar, A. J. et al. Soft, skin-interfaced microfluidic systems with passive galvanic stopwatches for precise chronometric sampling of sweat. Adv. Mater. 31, 1902109 (2019).

    Google Scholar 

  45. 45.

    Kong, Y., Wang, C., Yang, Y., Too, C. O. & Wallace, G. G. A battery composed of a polypyrrole cathode and a magnesium alloy anode—toward a bioelectric battery. Synth. Met. 162, 584–589 (2012).

    Google Scholar 

  46. 46.

    Williams, G. & McMurray, H. N. Localized corrosion of magnesium in chloride-containing electrolyte studied by a scanning vibrating electrode technique. J. Electrochem. Soc. 155, C340–C349 (2008).

    Google Scholar 

  47. 47.

    Huang, W. et al. Nanostructural and electrochemical evolution of the solid-electrolyte interphase on CuO nanowires revealed by cryogenic-electron microscopy and impedance spectroscopy. ACS Nano 13, 737–744 (2018).

    Google Scholar 

  48. 48.

    Cong, G., Wang, W., Lai, N.-C., Liang, Z. & Lu, Y.-C. A high-rate and long-life organic–oxygen battery. Nat. Mater. 18, 390 (2019).

    Google Scholar 

  49. 49.

    Peng, G. S., Chen, K. H., Fang, H. C., Chao, H. & Chen, S. Y. EIS study on pitting corrosion of 7150 aluminum alloy in sodium chloride and hydrochloric acid solution. Mater. Corros. 61, 783–789 (2010).

    Google Scholar 

  50. 50.

    Brett, C. M. A. On the electrochemical behaviour of aluminium in acidic chloride solution. Corros. Sci. 33, 203–210 (1992).

    Google Scholar 

  51. 51.

    Choi, D.-H., Kim, J. S., Cutting, G. R. & Searson, P. C. Wearable potentiometric chloride sweat sensor: the critical role of the salt bridge. Anal. Chem. 88, 12241–12247 (2016).

    Google Scholar 

  52. 52.

    Choi, J. et al. Soft, skin-mounted microfluidic systems for measuring secretory fluidic pressures generated at the surface of the skin by eccrine sweat glands. Lab Chip 17, 2572–2580 (2017).

    Google Scholar 

  53. 53.

    Twine, N. B. et al. Open nanofluidic films with rapid transport and no analyte exchange for ultra-low sample volumes. Lab Chip 18, 2816–2825 (2018).

    Google Scholar 

  54. 54.

    Wang, R. et al. Accuracy of wrist-worn heart rate monitors. JAMA Cardiol. 2, 104–106 (2017).

    Google Scholar 

  55. 55.

    Emaminejad, S. et al. Autonomous sweat extraction and analysis applied to cystic fibrosis and glucose monitoring using a fully integrated wearable platform. Proc. Natl Acad. Sci. USA 114, 4625–4630 (2017).

    Google Scholar 

Download references


This research was funded by the Air Force Research Laboratory (AFRL) Human Signatures Branch through Core funds provided to Northwestern University under contract FA8650-14-D-6516. S.W., T.H. and S.M. acknowledge support from the ‘Top Open’ programme (Tsinghua University, P. R. China), the visiting scholar programme (grant no. 201706235005, China Scholarship Council) and the Indo-US Science and Technology Forum (grant no. SERB-IUSSTF-2017/192) respectively. This work utilized the Northwestern University Micro/Nano Fabrication Facility (NUFAB), which is partially supported by the Soft and Hybrid Nanotechnology Experimental (SHyNE) resource (NSF ECCS-1542205), the Materials Research Science and Engineering Center (DMR-1720139), the State of Illinois and Northwestern University.

Author information




J.A.R., A.J.B., R.G. and S.P.L. conceived the project, designed the studies and analysed and interpreted the data. A.J.B. designed and developed the batteries, microfluidics, pH sensor and chloride sensor. S.P.L. designed and developed the electronics. W.L. developed the firmware. A.J.B., I.H., S.W., T.H., S.M. and N.N. worked on testing and optimizing the batteries. S.P.L., C.-J.S. and P.G. worked on fabricating and testing of the electronics. A.J.B. and J.C. worked on fabricating the microfluidics. J.K. assisted in optical studies. W.J.J., J.T.R. and R.T. assisted in testing the devices. A.J.B., S.P.L., W.J.J., I.H., R.G. and J.A.R. composed the manuscript.

Corresponding authors

Correspondence to R. Ghaffari or J. A. Rogers.

Ethics declarations

Competing interests

J.A.R., S.P.L., W.L. and R.G. are cofounders and/or employees of Epicore Biosystems, Inc., a company that pursues commercialization of microfluidic devices for wearable applications.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Figs. 1–9, discussion, equations and Table 1.

Reporting Summary

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Bandodkar, A.J., Lee, S.P., Huang, I. et al. Sweat-activated biocompatible batteries for epidermal electronic and microfluidic systems. Nat Electron (2020). https://doi.org/10.1038/s41928-020-0443-7

Download citation