Self-healing hydrogels use spontaneous intermolecular forces to recover from physical damage caused by extreme strain, pressure or tearing. Such materials are of potential use in soft robotics and tissue engineering, but they have relatively low electrical conductivity, which limits their application in stretchable and mechanically robust circuits. Here we report an organogel composite that is based on poly(vinyl alcohol)–sodium borate and has high electrical conductivity (7 × 104 S m−1), low stiffness (Young’s modulus of ~20 kPa), high stretchability (strain limit of >400%) and spontaneous mechanical and electrical self-healing. The organogel matrix is embedded with silver microflakes and gallium-based liquid metal microdroplets, which form a percolating network, leading to high electrical conductivity in the material. We also overcome the rapid drying problem of the hydrogel material system by replacing water with an organic solvent (ethylene glycol), which avoids dehydration and property changes for over 24 h in an ambient environment. We illustrate the capabilities of the self-healing organogel composite by using it in a soft robot, a soft circuit and a reconfigurable bioelectrode.
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The customized tracking algorithm and EMG sensing data-processing code used in this work are available at https://drive.google.com/drive/folders/1DG0Ev9oP3RWoiptVC6TepfWJDQI7y235?usp=sharing.
Terryn, S. et al. A review on self-healing polymers for soft robotics. Mater. Today 47, 187–205 (2021).
Bartlett, M. D., Dickey, M. D. & Majidi, C. Self-healing materials for soft-matter machines and electronics. NPG Asia Mater. 11, 21 (2019).
Chen, J., Huang, Y., Ma, X. & Lei, Y. Functional self-healing materials and their potential applications in biomedical engineering. Adv. Compos. Hybrid. Mater. 1, 94–113 (2018).
Idumah, C. I., Nwuzor, I. & Odera, S. R. Recent advancements in self-healing polymeric hydrogels, shape memory and stretchable materials. Int. J. Polymeric Mater. Polymeric Biomater. 70, 941–966 (2021).
Kanu, N. J., Gupta, E., Vates, U. K. & Singh, G. K. Self-healing composites: a state-of-the-art review. Compos. A Appl. Sci. Manuf. 121, 474–486 (2019).
Cao, Y. et al. Self-healing electronic skins for aquatic environments. Nat. Electron. 2, 75–82 (2019).
Yu, X. et al. Highly stretchable, ultra-soft and fast self-healable conductive hydrogels based on polyaniline nanoparticles for sensitive flexible sensors. Adv. Funct. Mater. 32, 2204366 (2022).
Hao, X. P. et al. Healable, recyclable and multifunctional soft electronics based on biopolymer hydrogel and patterned liquid metal. Small 18, 2201643 (2022).
Deng, Z., Wang, H., Ma, P. X. & Guo, B. Self-healing conductive hydrogels: preparation, properties and applications. Nanoscale 12, 1224–1246 (2020).
Zhang, A. et al. Research status of selfhealing hydrogel for wound management: a review. Int. J. Biol. Macromol. 164, 2108–2123 (2020).
Zhang, Z. et al. Highly transparent, self-healable and adhesive organogels for bio-inspired intelligent ionic skins. ACS Appl. Mater. Interfaces 12, 15657–15666 (2020).
Polachan, K., Chatterjee, B., Weigand, S. & Sen, S. Human body-electrode interfaces for wide-frequency sensing and communication: a review. Nanomaterials 11, 2152 (2021).
Zhang, X. et al. Supramolecular nanofibrillar hydrogels as highly stretchable, elastic and sensitive ionic sensors. Mater. Horiz. 6, 326–333 (2019).
Liu, K. et al. Ultrasoft self-healing nanoparticle-hydrogel composites with conductive and magnetic properties. ACS Sustain. Chem. Eng. 6, 6395–6403 (2018).
Lim, C. et al. Stretchable conductive nanocomposite based on alginate hydrogel and silver nanowires for wearable electronics. APL Mater. 7, 031502 (2018).
Zhao, W. et al. 3D printing of stretchable, adhesive and conductive Ti3C2Tx-polyacrylic acid hydrogels. Polymers 14, 1992 (2022).
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).
Li, P. et al. Stretchable all-gel-state fiber-shaped supercapacitors enabled by macromolecularly interconnected 3D graphene/nanostructured conductive polymer hydrogels. Adv. Mater. 30, 1800124 (2018).
Deng, Z. et al. Stimuli-responsive conductive nanocomposite hydrogels with high stretchability, self-healing, adhesiveness, and 3D printability for human motion sensing. ACS Appl. Mater. Interfaces 11, 6796–6808 (2019).
Dai, S., Zhou, X., Wang, S., Ding, J. & Yuan, N. A self-healing conductive and stretchable aligned carbon nanotube/hydrogel composite with a sandwich structure. Nanoscale 10, 19360–19366 (2018).
Yang, W. et al. Robust and mechanically and electrically self-healing hydrogel for efficient electromagnetic interference shielding. ACS Appl. Mater. Interfaces 10, 8245–8257 (2018).
Chen, J., Peng, Q., Thundat, T. & Zeng, H. Stretchable, injectable and self-healing conductive hydrogel enabled by multiple hydrogen bonding toward wearable electronics. Chem. Mater. 31, 4553–4563 (2019).
Dispenza, C. et al. Electrically conductive hydrogel composites made of polyaniline nanoparticles and poly(N-vinyl-2-pyrrolidone). Polymer 47, 961–971 (2006).
Yang, Q., Hu, Z. & Rogers, J. A. Functional hydrogel interface materials for advanced bioelectronic devices. Acc. Mater. Res. 2, 1010–1023 (2021).
Cai, S. et al. Soft liquid metal infused conductive sponges. Adv. Mater. Technol. 7, 2101500 (2022).
Ohm, Y. et al. An electrically conductive silver–polyacrylamide–alginate hydrogel composite for soft electronics. Nat. Electron. 4, 185–192 (2021).
Fassler, A. & Majidi, C. Liquid-phase metal inclusions for a conductive polymer composite. Adv. Mater. 27, 1928–1932 (2015).
Majidi, C., Alizadeh, K., Ohm, Y., Silva, A. & Tavakoli, M. Liquid metal polymer composites: from printed stretchable circuits to soft actuators. Flex. Print. Electron. 7, 013002 (2022).
Tang, S.-Y., Tabor, C., Kalantar-Zadeh, K. & Dickey, M. D. Gallium liquid metal: the devil’s elixir. Annu. Rev. Mater. Res. 51, 381–408 (2021).
Park, J.-E. et al. Rewritable, printable conducting liquid metal hydrogel. ACS Nano 13, 9122–9130 (2019).
Liao, M., Liao, H., Ye, J., Wan, P. & Zhang, L. Polyvinyl alcohol-stabilized liquid metal hydrogel for wearable transient epidermal sensors. ACS Appl. Mater. Interfaces 11, 47358–47364 (2019).
Ford, M. J. et al. Controlled assembly of liquid metal inclusions as a general approach for multifunctional composites. Adv. Mater. 32, 2002929 (2020).
Chen, Y. et al. A gradient-distributed liquid-metal hydrogel capable of tunable actuation. Chem. Eng. J. 421, 127762 (2021).
Xu, J. et al. Polymerization of moldable self-healing hydrogel with liquid metal nanodroplets for flexible strain-sensing devices. Chem. Eng. J. 392, 123788 (2020).
Peng, H., Xin, Y., Xu, J., Liu, H. & Zhang, J. Ultra-stretchable hydrogels with reactive liquid metals as asymmetric force-sensors. Mater. Horiz. 6, 618–625 (2019).
Xu, Y. et al. Convergent synthesis of diversified reversible network leads to liquid metal-containing conductive hydrogel adhesives. Nat. Commun. 12, 2407 (2021).
Spoljaric, S., Salminen, A., Luong, N. D. & Seppälä, J. Stable, self-healing hydrogels from nanofibrillated cellulose, poly(vinyl alcohol) and borax via reversible crosslinking. Eur. Polym. J. 56, 105–117 (2014).
Hassan, C. M. & Peppas, N. A. Structure and morphology of freeze/thawed PVA hydrogels. Macromolecules 33, 2472–2479 (2000).
Hung, W.-L., Wang, D.-M., Lai, J.-Y. & Chou, S.-C. On the initiation of macrovoids in polymeric membranes—effect of polymer chain entanglement. J. Membr. Sci. 505, 70–81 (2016).
Bercea, M., Morariu, S. & Rusu, D. In situ gelation of aqueous solutions of entangled poly(vinyl alcohol). Soft Matter 9, 1244–1253 (2013).
Rusdi, M., Moroi, Y., Nakahara, H. & Shibata, O. Evaporation from water-ethylene glycol liquid mixture. Langmuir 21, 7308–7310 (2005).
Chen, H., Ren, X. & Gao, G. Skin-inspired gels with toughness, antifreezing, conductivity and remoldability. ACS Appl. Mater. Interfaces 11, 28336–28344 (2019).
Rong, Q. et al. Anti-freezing, conductive self-healing organohydrogels with stable strain-sensitivity at subzero temperatures. Angew. Chem. Int. Ed. 56, 14159–14163 (2017).
Dillon, P. F. Biophysics: A Physiological Approach (Cambridge Univ. Press, 2012).
.Samal, S. Effect of shape and size of filler particle on the aggregation and sedimentation behavior of the polymer composite. Powder Technol. 366, 43–51 (2020).
Wang, J. et al. Printable superelastic conductors with extreme stretchability and robust cycling endurance enabled by liquid-metal particles. Adv. Mater. 30, 1706157 (2018).
Hajalilou, A. et al. Biphasic liquid metal composites for sinter-free printed stretchable electronics. Adv. Mater. Interfaces 9, 2101913 (2022).
Zu, W. et al. A comparative study of silver microflakes in digitally printable liquid metal embedded elastomer inks for stretchable electronics. Adv. Mater. Technol. 7, 2200534 (2022).
Lynne Taylor, D. & Panhuis, Minhet Self-healing hydrogels. Adv. Mater. 28, 90609093 (2016).
This work was partially funded by the Air Force Research Lab (AFRL) through the National Bio Materials Consortium (NBMC) under grant no. NB18-21-33.
The authors declare no competing interests.
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Zhao, Y., Ohm, Y., Liao, J. et al. A self-healing electrically conductive organogel composite. Nat Electron 6, 206–215 (2023). https://doi.org/10.1038/s41928-023-00932-0
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