Abstract
Gelatinous underwater invertebrates such as jellyfish have organs that are transparent, stretchable, touch-sensitive and self-healing, which allow the creatures to navigate, camouflage themselves and, indeed, survive in aquatic environments. Artificial skins that emulate such functionality could be used to develop applications such as aquatic soft robots and water-resistant human–machine interfaces. Here we report a bio-inspired skin-like material that is transparent, electrically conductive and can autonomously self-heal in both dry and wet conditions. The material, which is composed of a fluorocarbon elastomer and a fluorine-rich ionic liquid, has an ionic conductivity that can be tuned to as high as 10−3 S cm−1 and can withstand strains as high as 2,000%. Owing to ion–dipole interactions, it offers fast and repeatable electro-mechanical self-healing in wet, acidic and alkali environments. To illustrate the potential applications of the approach, we used our electronic skins to create touch, pressure and strain sensors. We also show that the material can be printed into soft and pliable ionic circuit boards.
This is a preview of subscription content, access via your institution
Access options
Access Nature and 54 other Nature Portfolio journals
Get Nature+, our best-value online-access subscription
$29.99 / 30 days
cancel any time
Subscribe to this journal
Receive 12 digital issues and online access to articles
$119.00 per year
only $9.92 per issue
Rent or buy this article
Prices vary by article type
from$1.95
to$39.95
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
Data availability
The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.
References
Larson, C. et al. Highly stretchable electroluminescent skin for optical signaling and tactile sensing. Science 351, 1071–1074 (2016).
Bauer, S. et al. 25th Anniversary Article: a soft future: from robots and sensor skin to energy harvesters. Adv. Mater. 26, 149–162 (2014).
Morin, S. A. et al. Camouflage and display for soft machines. Science 337, 828–832 (2012).
Yuk, H., Zhang, T., Parada, G. A., Liu, X. & Zhao, X. Skin-inspired hydrogel–elastomer hybrids with robust interfaces and functional microstructures. Nat. Commun. 7, 12028 (2016).
Kim, C.-C., Lee, H.-H., Oh, K. H. & Sun, J.-Y. Highly stretchable, transparent ionic touch panel. Science 353, 682–687 (2016).
Wang, S. et al. Skin electronics from scalable fabrication of an intrinsically stretchable transistor array. Nature 555, 83–88 (2018).
Tee, B. C. K. et al. Tunable flexible pressure sensors using microstructured elastomer geometries for intuitive electronics. Adv. Funct. Mater. 24, 5427–5434 (2014).
Gao, W. et al. Fully integrated wearable sensor arrays for multiplexed in situ perspiration analysis. Nature 529, 509–514 (2016).
Schwartz, G. et al. Flexible polymer transistors with high pressure sensitivity for application in electronic skin and health monitoring. Nat. Commun. 4, 1859 (2013).
Chen, L. Y. et al. Continuous wireless pressure monitoring and mapping with ultra-small passive sensors for health monitoring and critical care. Nat. Commun. 5, 1–10 (2014).
Lipomi, D. J. et al. Skin-like pressure and strain sensors based on transparent elastic films of carbon nanotubes.Nat. Nanotechnol. 6, 788–792 (2011).
Sekitani, T., Zschieschang, U., Klauk, H. & Someya, T. Flexible organic transistors and circuits with extreme bending stability. Nat. Mater. 9, 1015–1022 (2010).
Kim, K. S. et al. Large-scale pattern growth of graphene films for stretchable transparent electrodes. Nature 457, 706–710 (2009).
Baik, S. et al. A wet-tolerant adhesive patch inspired by protuberances in suction cups of octopi. Nature 546, 396–400 (2017).
Tan, Y. J., Wu, J., Li, H. & Tee, B. C. K. Self-healing electronic materials for a smart and sustainable future. ACS Appl. Mater. Interfaces 10, 15331–15345 (2018).
Patrick, J. F., Robb, M. J., Sottos, N. R., Moore, J. S. & White, S. R. Polymers with autonomous life-cycle control. Nature 540, 363–370 (2016).
Oh, J. Y. et al. Intrinsically stretchable and healable semiconducting polymer for organic transistors. Nature 539, 411–415 (2016).
Bandodkar, A. J. et al. All-printed magnetically self-healing electrochemical devices. Sci. Adv 2, e1601465 (2016).
Tee, B. C. K., Wang, C., Allen, R. & Bao, Z. An electrically and mechanically self-healing composite with pressure- and flexion-sensitive properties for electronic skin applications. Nat. Nanotechnol. 7, 825–832 (2012).
Kang, J. et al. Tough and water-insensitive self-healing elastomer for robust electronic skin. Adv. Mater. 30, 1706846 (2018).
Cao, Y. et al. A highly stretchy, transparent elastomer with the capability to automatically self-heal underwater. Adv. Mater. 30, 1804602 (2018).
Lipomi, D. J. et al. Electronic properties of transparent conductive films of PEDOT:PSS on stretchable substrates. Chem. Mater. 24, 373–382 (2012).
Keplinger, C. et al. Stretchable, transparent, ionic conductors. Science 341, 984–987 (2013).
Sun, J.-Y., Keplinger, C., Whitesides, G. M. & Suo, Z. Ionic skin. Adv. Mater. 26, 7608–7614 (2014).
Wirthl, D. et al. Instant tough bonding of hydrogels for soft machines and electronics. Sci. Adv. 3, 1–10 (2017).
Taylor, D. L. & Het Panhuis, M. Self-healing hydrogels. Adv. Mater. 28, 9060–9093 (2016).
Kaartvedt, S. et al. Social behaviour in mesopelagic jellyfish. Sci. Rep. 5, 11310 (2015).
Johnsen, S. Transparent animals. Sci. Am. 282, 80–89 (2000).
Cao, Y. et al. A transparent, self‐healing, highly stretchable ionic conductor. Adv. Mater. 29, 1605099 (2017).
Cordier, P., Tournilhac, F., Soulié-Ziakovic, C. & Leibler, L. Self-healing and thermoreversible rubber from supramolecular assembly. Nature 451, 977–980 (2008).
Li, C.-H. et al. A highly stretchable autonomous self-healing elastomer. Nat. Chem. 8, 618–624 (2016).
Earle, M. J. et al. The distillation and volatility of ionic liquids. Nature 439, 831–834 (2006).
Tee, B. C. K. et al. A skin-inspired organic digital mechanoreceptor. Science 350, 313–316 (2015).
Katzschmann, R. K., DelPreto, J., MacCurdy, R. & Rus, D. Exploration of underwater life with an acoustically controlled soft robotic fish. Sci. Robot. 3, eaar3449 (2018).
Li, H., Tan, Y. J., Leong, K. F. & Li, L. 3D bioprinting of highly thixotropic alginate/methylcellulose hydrogel with strong interface bonding. ACS Appl. Mater. Interfaces 9, 20086–20097 (2017).
Acknowledgements
B.C.-K.T. is grateful for the support of a National Research Foundation Fellowship by the Singapore National Research Foundation (NRF) Prime Minister’s Office, and the National University of Singapore (NUS) Startup Grant. H.C.G. acknowledges support from a NUS NGS Scholarship. C.W. acknowledges support from NSFC grant no. 21890731. We thank J.Y. Sun for discussions and S. Wang, J. Tan, H. Li and W. Yan for access to testing equipment.
Author information
Authors and Affiliations
Contributions
B.C.-K.T., C.W., Y.C., and Y.J.T. conceived and designed the experiments; Y.C., Y.J.T., S.L. and W.W.L. carried out experiments and collected the overall data; Y.C., Y.J.T. and H.C.G. contributed to materials fabrication and characterization. S.L., W.W.L. and Y.J.T. performed electrical properties characterization and worked on sensors demonstration. S.L. and Y.J.T. worked on transparent and self-healable soft PCB. Y.Q.C. contributed the DFT calculations. Y.J.T., B.C.-K.T., Y.C., S.L. and C.W. analysed all the data and co-wrote the paper. All authors discussed the results and commented on the manuscript.
Corresponding authors
Ethics declarations
Competing interests
The authors declare no competing interests.
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 Notes 1–4, Supplementary Tables 1–4 and Supplementary Figures 1–22
Supplementary Video 1
Autonomous self-healing of GLASSES. The video starts with a time-lapse capture with the transparent material laid on a picture, then a puncture is made through the material. The material is observed under a microscope for three days. It self-heals without any external stimuli such as pressure, temperature or organic solvents. After that, a new piece of material is bifurcated, and self-healed. The material can be stretched again after healing in ambient conditions for 24 hours.
Supplementary Video 2
Playing a snake game on the GLASSES touch panel. The position of touch and swipe actions of a finger can be sensed by the material for human–machine interactions.
Supplementary Video 3
The position of touch can be sensed by the transparent material by utilizing its surface capacitance system and external amplifying circuits, which is used to make a drawing panel.
Supplementary Video 4
Conformable pressure sensor linked to LEDs for visualization of changes in pressure and touch locations. When the fingertip touches the material, a surface capacitance is introduced. When the fingertip presses down on the material, the contact area increases as the material is deformable, resulting in an increase in surface capacitance.
Supplementary Video 5
GLASSES material used as a strain sensor with optically encoded signal output. The frequency signal is changing with strain.
Supplementary Video 6
GLASSES is made into a strain sensor, and is transparent and able to send out optical communication information of its strain state. This video is a demonstration of an infrared communication system in air and water, and the signal–strain plot showing that the transmitted signal carrying information (frequency) is dependent on the strain. The display on the phone shows the balloon status. The infrared signal is directed through GLASSES only. As demonstrated in the beginning of the video, the signal is interrupted when the balloon is being tilted as the infrared LED is not aligned with the receiver. The status shows ‘Expanding’ when the balloon starts to expand, corresponding to a decrease in frequency output. We also show that the demonstration works when the GLASSES are submerged in water. After touching the water surface, the display changes to ‘In water’, correlating to a sudden increase of frequency output. When the frequency signal decrease again, the status changes to ‘Expanding in water’.
Supplementary Video 7
Self-healed GLASSES (with LED) submerged in water as an unobtrusive soft ‘robot’ among small underwater creatures. The transparent materials allow light to transmit through them. The multiple self-healed regions remain intact underwater. The LED-embedded GLASSES mimics the bioluminescence of jellyfish underwater, sending messages to the shrimps that they react to by escaping from the bright ‘jellyfish’. The same setup is repeated by using LEDs embedded in an opaque material, where the shrimps did not visibly react when the LEDs are turned on because the light cannot transmit through the material. The shrimps reacted only after the opaque material is ‘toppled’, when the light intensity suddenly increases.
Supplementary Video 8
GLASSES material can be printed into soft, stretchable, transparent PCB. The PCB can be mechanically twisted and stretched.
Rights and permissions
About this article
Cite this article
Cao, Y., Tan, Y.J., Li, S. et al. Self-healing electronic skins for aquatic environments. Nat Electron 2, 75–82 (2019). https://doi.org/10.1038/s41928-019-0206-5
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/s41928-019-0206-5
This article is cited by
-
Ultrafast underwater self-healing piezo-ionic elastomer via dynamic hydrophobic-hydrolytic domains
Nature Communications (2024)
-
Robot, repair thyself: laying the foundations for self-healing machines
Nature (2024)
-
Self-healable gels in electrochemical energy storage devices
Nano Research (2024)
-
Unlocking Intrinsic Conductive Dynamics of Ionogel Microneedle Arrays as Wearable Electronics for Intelligent Fire Safety
Advanced Fiber Materials (2024)
-
An interfacial robust and entire self-healing ionogel-elastomer hybrid for elastic electronics enables discretionary assembly and reconfiguration
Science China Chemistry (2024)