Abstract
Conductive hydrogels can be used to make electrodes that interface with biological tissues due to their similar mechanical properties and high electrical conductivity in physiological environments. The electrical and mechanical properties of conductive hydrogels have improved in recent years, but they still suffer from poor durability and reliability, particularly in wet environments. Here we show that high-stability conductive hydrogels can be fabricated and adhered to various substrates using laser-induced phase separation and interface structures. With this approach, conducting polymers can be selectively transformed into conductive hydrogels with wet conductivities of 101.4 S cm−1 and patterned with a spatial resolution down to 5 μm. The conductive hydrogels exhibit high robustness, maintaining their electrochemical properties after 1 h of ultrasonication and 8 months of storage in water. They also exhibit peel and lap-shear strength in wet conditions of 64.4 N m−1 and 62.1 kPa, respectively. We used the conductive hydrogels to make microelectrode arrays that can stably record electrophysiological signals over 3 weeks in rat brains and hearts. The hydrogel electrodes can also be reused through intensive ultrasonication cleaning due to their durability.
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Data availability
The data that support the findings of this study are available from the corresponding author upon reasonable request.
References
Chen, R., Canales, A. & Anikeeva, P. Neural recording and modulation technologies. Nat. Rev. Mater. 2, 16093 (2017).
Lin, M., Hu, H., Zhou, S. & Xu, S. Soft wearable devices for deep-tissue sensing. Nat. Rev. Mater. 7, 850–869 (2022).
Pyun, K. R., Rogers, J. A. & Ko, S. H. Materials and devices for immersive virtual reality. Nat. Rev. Mater. 7, 841–843 (2022).
Yuk, H., Lu, B. & Zhao, X. Hydrogel bioelectronics. Chem. Soc. Rev. 48, 1642–1667 (2019).
Cuttaz, E. et al. Conductive elastomer composites for fully polymeric, flexible bioelectronics. Biomater. Sci. 7, 1372–1385 (2019).
Choi, S. et al. Highly conductive, stretchable and biocompatible Ag-Au core-sheath nanowire composite for wearable and implantable bioelectronics. Nat. Nanotechnol. 13, 1048–1056 (2018).
Navaei, A. et al. Gold nanorod-incorporated gelatin-based conductive hydrogels for engineering cardiac tissue constructs. Acta Biomater. 41, 133–146 (2016).
Zhang, L. & Shi, G. Preparation of highly conductive graphene hydrogels for fabricating supercapacitors with high rate capability. J. Phys. Chem. C 115, 17206–17212 (2011).
Feig, V. R., Tran, H., Lee, M. & Bao, Z. Mechanically tunable conductive interpenetrating network hydrogels that mimic the elastic moduli of biological tissue. Nat. Commun. 9, 2740 (2018).
Ido, Y. et al. Conducting polymer microelectrodes anchored to hydrogel films. ACS Macro Lett. 1, 400–403 (2012).
Zhou, Z., Yuan, W. & Xie, X. A stretchable and adhesive composite hydrogel containing PEDOT:PSS for wide-range and precise motion sensing and electromagnetic interference shielding and as a triboelectric nanogenerator. Mater. Chem. Front. 6, 3359–3368 (2022).
Solazzo, M. et al. PEDOT:PSS interfaces stabilised using a PEGylated crosslinker yield improved conductivity and biocompatibility. J. Mater. Chem. B 7, 4811–4820 (2019).
Lu, B. et al. Pure PEDOT:PSS hydrogels. Nat. Commun. 10, 1043 (2019).
Liu, Y. et al. Soft and elastic hydrogel-based microelectronics for localized low-voltage neuromodulation. Nat. Biomed. Eng. 3, 58–68 (2019).
Won, D. et al. Digital selective transformation and patterning of highly conductive hydrogel bioelectronics by laser-induced phase separation. Sci. Adv. 8, eabo3209 (2022).
Yuk, H. et al. 3D printing of conducting polymers. Nat. Commun. 11, 1604 (2020).
Ganji, M. et al. Monolithic and scalable Au nanorod substrates improve PEDOT-metal adhesion and stability in neural electrodes. Adv. Healthc. Mater. 7, e1800923 (2018).
Pranti, A. S., Schander, A., Bödecker, A. & Lang, W. in Proc. Eurosensors 2017 (eds. Viricelle J. P. et al.) 492 (MDPI, 2017).
Inoue, A., Yuk, H., Lu, B. & Zhao, X. Strong adhesion of wet conducting polymers on diverse substrates. Sci. Adv. 6, eaay5394 (2020).
Ouyang, L. et al. Enhanced PEDOT adhesion on solid substrates with electrografted P(EDOT-NH2). Sci. Adv. 3, e1600448 (2017).
Tan, P. et al. Solution-processable, soft, self-adhesive, and conductive polymer composites for soft electronics. Nat. Commun. 13, 358 (2022).
Hong, G. & Lieber, C. M. Novel electrode technologies for neural recordings. Nat. Rev. Neurosci. 20, 330–345 (2019).
Zheng, Y. Q. et al. Monolithic optical microlithography of high-density elastic circuits. Science 373, 88–94 (2021).
Jiang, Y. et al. Topological supramolecular network enabled high-conductivity, stretchable organic bioelectronics. Science 375, 1411–1417 (2022).
Zhou, T. et al. 3D printable high-performance conducting polymer hydrogel for all-hydrogel bioelectronic interfaces. Nat. Mater. 22, 895–902 (2023).
Teo, M. Y. et al. Direct patterning of highly conductive PEDOT:PSS/ionic liquid hydrogel via microreactive inkjet printing. ACS Appl. Mater. Interfaces 11, 37069–37076 (2019).
Liu, S., Rao, Y., Jang, H., Tan, P. & Lu, N. Strategies for body-conformable electronics. Matter 5, 1104–1136 (2022).
Jiang, Y. et al. A universal interface for plug-and-play assembly of stretchable devices. Nature 614, 456–462 (2023).
Won, D. et al. Transparent electronics for wearable electronics application. Chem. Rev. 123, 9982–10078 (2023).
Kim, S. M. et al. Influence of PEDOT:PSS crystallinity and composition on electrochemical transistor performance and long-term stability. Nat. Commun. 9, 3858 (2018).
Xu, S. et al. High-performance PEDOT:PSS flexible thermoelectric materials and their devices by triple post-treatments. Chem. Mater. 31, 5238–5244 (2019).
Waite, J. H. Nature’s underwater adhesive specialist. Int. J. Adhes. Adhes. https://doi.org/10.1016/0143-7496(87)90048-0 (1987).
Wang, B. et al. Development and characterization of a novel low-cost water-level and water quality monitoring sensor by using enhanced screen printing technology with PEDOT:PSS. Micromachines (Basel) https://doi.org/10.3390/mi11050474 (2020).
Modarresi, M., Mehandzhiyski, A., Fahlman, M., Tybrandt, K. & Zozoulenko, I. Microscopic understanding of the granular structure and the swelling of PEDOT:PSS. Macromolecules 53, 6267–6278 (2020).
De Lorenzis, L. & Zavarise, G. Modeling of mixed-mode debonding in the peel test applied to superficial reinforcements. Int. J. Solids Struct. https://doi.org/10.1016/j.ijsolstr.2008.05.024 (2008).
Wei, B. et al. Significant enhancement of PEDOT thin film adhesion to inorganic solid substrates with EDOT-acid. ACS Appl. Mater. Interfaces 7, 15388–15394 (2015).
Zhang, L. et al. Fully organic compliant dry electrodes self-adhesive to skin for long-term motion-robust epidermal biopotential monitoring. Nat. Commun. 11, 4683 (2020).
Ma, H. et al. 3D printing of PEDOT:PSS-PU-PAA hydrogels with excellent mechanical and electrical performance for EMG electrodes. in Intelligent Robotics and Applications. ICIRA 2022. Lecture Notes in Computer Science (eds. Liu, H. et al.) https://doi.org/10.1007/978-3-031-13822-5_26 (Springer, 2022).
Sun, F. et al. Highly transparent, adhesive, stretchable and conductive PEDOT:PSS/polyacrylamide hydrogels for flexible strain sensors. Colloids Surfaces A https://doi.org/10.1016/j.colsurfa.2021.126897 (2021).
Cui, X. T. & Zhou, D. D. Poly (3,4-ethylenedioxythiophene) for chronic neural stimulation. IEEE Trans Neural Syst. Rehabil. Eng. https://doi.org/10.1109/TNSRE.2007.909811 (2007).
Boehler, C. et al. Long-term stable adhesion for conducting polymers in biomedical applications: IrOx and nanostructured platinum solve the chronic challenge. ACS Appl. Mater Interfaces. https://doi.org/10.1021/acsami.6b13468 (2017).
Viswam, V., Obien, M. E. J., Franke, F., Frey, U. & Hierlemann, A. Optimal electrode size for multi-scale extracellular-potential recording from neuronal assemblies. Front. Neurosci. 13, 385 (2019).
Ludwig, K. A., Uram, J. D., Yang, J., Martin, D. C. & Kipke, D. R. Chronic neural recordings using silicon microelectrode arrays electrochemically deposited with a poly(3,4-ethylenedioxythiophene) (PEDOT) film. J. Neural Eng. 3, 59–70 (2006).
Acknowledgements
This study was supported by the National Research Foundation of Korea (Grant Nos. 2021R1A2B5B03001691 to S.H.K. and 2022R1A2C3009087 to T.-S.K.). This study was also supported by Grant Nos. 2021R1A2C1008257 (C.-Y.K.) and RS-2023-00210865 (J.C.).
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D.W. and HJ.K. designed and carried out the projects. H.K. and J.C. designed and performed the MD simulations. J.K. and M.W.K. carried out the in vivo experiments and were advised by C.-Y.K. J.A. performed the heat transfer simulations. K.M. and S.H. set the optical system for high resolution and performed the experiments. Y.L. performed the imaging characterizations. T.-S.K. and S.H.K. supervised the research programme. All authors discussed the results and jointly wrote the manuscript.
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Nature Electronics thanks Nan Liu, Kaichen Xu and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
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Extended data
Extended Data Fig. 1 TEM image of PEDOT:PSS surface by LIPSA before and after EG treatment.
(A) TEM images of PEDOT:PSS before EG treatment. (B) TEM images of PEDOT:PSS after EG treatment.
Extended Data Fig. 2 XRD data of pristine PEDOT:PSS, laser-treated PEDOT:PSS before and after EG treatment.
No distinct difference in XRD peaks is found after LIPSP.
Extended Data Fig. 3 High-resolution patterning results using a tightly focused laser beam by the objective lens.
(A) Optical microscope images of dried PEDOT:PSS hydrogel patterns, (B) AFM topography of dried PEDOT:PSS hydrogels patterns.
Extended Data Fig. 4 Characterization of the PET substrates after laser process and bulk annealing.
(A) Cross-sectional SEM image of PEDOT:PSS and PET interfaces. (B) EDS analysis of interfaces on PET-side after delaminating PEDOT:PSS. (C) EDS analysis on the interfaces on the PET side in cross-sectional view.
Extended Data Fig. 5 Effect of EG post-treatment on adhesion force of PEDOT:PSS hydrogels to substrates.
(A) Lap-shear strength of PEDOT:PSS hydrogels before and after EG treatments. (B) The weak layer generated inside PEDOT:PSS causes cohesive fractures.
Supplementary information
Supplementary Information
Supplementary Notes 1–5, Figs. 1–28 and Videos 1–4.
Supplementary Video 1
Strong wet adhesion of pure PEDOT:PSS hydrogels by LIPSA.
Supplementary Video 2
Weak adhesion of bulk-annealed PEDOT:PSS hydrogels.
Supplementary Video 3
Robust adhesion of micropatterned pure PEDOT:PSS hydrogels.
Supplementary Video 4
Robust adhesion of micropatterned pure PEDOT:PSS hydrogels under mechanical stimuli.
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Won, D., Kim, H., Kim, J. et al. Laser-induced wet stability and adhesion of pure conducting polymer hydrogels. Nat Electron (2024). https://doi.org/10.1038/s41928-024-01161-9
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DOI: https://doi.org/10.1038/s41928-024-01161-9
