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SCIENTIA SINICA Informationis, Volume 48 , Issue 6 : 650-669(2018) https://doi.org/10.1360/N112018-00117

Recent advances in flexible self-healing materials and sensors

Ting ZHANG *, Yuanyuan BAI , Fuqin SUN
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  • ReceivedMay 7, 2018
  • AcceptedMay 18, 2018
  • PublishedJun 12, 2018
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Abstract


Funded by

国家自然科学基金(61574163)

江苏省杰出青年基金(BK20170008)

江苏省六大人才高峰(DZXX-082)


References

[1] Someya T, Bao Z N, Malliaras G G. The rise of plastic bioelectronics. Nature, 2016, 540: 379-385 CrossRef PubMed ADS Google Scholar

[2] Kim D H, Ghaffari R, Lu N. Flexible and stretchable electronics for biointegrated devices. Annu Rev Biomed Eng, 2012, 14: 113-128 CrossRef PubMed Google Scholar

[3] Amjadi M, Kyung K U, Park I. Stretchable, skin-mountable, and wearable strain sensors and their potential applications: a review. Adv Funct Mater, 2016, 26: 1678-1698 CrossRef Google Scholar

[4] Trung T Q, Lee N E. Flexible and stretchable physical sensor integrated platforms for wearable human-activity monitoringand personal healthcare. Adv Mater, 2016, 28: 4338-4372 CrossRef PubMed Google Scholar

[5] Wang X W, Liu Z, Zhang T. Flexible sensing electronics for wearable/attachable health monitoring. Small, 2017, 13: 1602790 CrossRef PubMed Google Scholar

[6] Yang T T, Xie D, Li Z H. Recent advances in wearable tactile sensors: Materials, sensing mechanisms, and device performance. Mater Sci Eng-R-Rep, 2017, 115: 1-37 CrossRef Google Scholar

[7] Li Q, Zhang L N, Tao X M. Review of flexible temperature sensing networks for wearable physiological monitoring. Adv Healthcare Mater, 2017, 6: 1601371 CrossRef PubMed Google Scholar

[8] Wu H, Huang Y A, Xu F. Energy harvesters for wearable and stretchable electronics: from flexibility to stretchability. Adv Mater, 2016, 28: 9881-9919 CrossRef PubMed Google Scholar

[9] Dubal D P, Chodankar N R, Kim D H. Towards flexible solid-state supercapacitors for smart and wearable electronics.. Chem Soc Rev, 2018, 47: 2065-2129 CrossRef PubMed Google Scholar

[10] Ahner J, Bode S, Micheel M, et al. Self-healing functional polymeric materials. Adv Polym Sci, 2016, 273: 247--283. Google Scholar

[11] Zhang L, Chandran B K, Chen X D. Self-healing electronic nanodevices. In: Soft Matter Nanotechnology: From Structure to Function. Weinheim: Wiley-VCH Verlag GmbH & Co. KGaA, 2015. 401--416. Google Scholar

[12] Luo C S, Wan P, Yang H. Healable transparent electronic devices. Adv Funct Mater, 2017, 27: 1606339 CrossRef Google Scholar

[13] Yang Y, Zhu B, Yin D. Flexible self-healing nanocomposites for recoverable motion sensor. Nano Energy, 2015, 17: 1-9 CrossRef Google Scholar

[14] Tee B C K, Wang C, Allen R. An electrically and mechanically self-healing composite with pressure- and flexion-sensitive properties for electronic skin applications. Nat Nanotech, 2012, 7: 825-832 CrossRef PubMed ADS Google Scholar

[15] Darabi M A, Khosrozadeh A, Mbeleck R, et al. Skin-inspired multifunctional autonomic-intrinsic conductive self-healing hydrogels with pressure sensitivity, stretchability, and 3D printability. Adv Mater, 2018, 30: 1700533. Google Scholar

[16] Bergman S D, Wudl F. Mendable polymers. J Mater Chem, 2008, 18: 41-62 CrossRef Google Scholar

[17] Wool R P. Self-healing materials: a review. Soft Matter, 2008, 4: 400-418 CrossRef ADS Google Scholar

[18] Wu D Y, Meure S, Solomon D. Self-healing polymeric materials: a review of recent developments. Prog Polymer Sci, 2008, 33: 479-522 CrossRef Google Scholar

[19] Li Y, Chen S S, Wu M C. Polyelectrolyte multilayers impart healability to highly electrically conductive films. Adv Mater, 2012, 24: 4578-4582 CrossRef PubMed Google Scholar

[20] Gong C K, Liang J J, Hu W. A healable, semitransparent silver nanowire-polymer composite conductor. Adv Mater, 2013, 25: 4186-4191 CrossRef PubMed Google Scholar

[21] Bai S L, Sun C Z, Yan H. Healable, transparent, room-temperature electronic sensors based on carbon nanotube network-coated polyelectrolyte multilayers. Small, 2015, 11: 5807-5813 CrossRef PubMed Google Scholar

[22] Huynh T P, Haick H. Self-healing, fully functional, and multiparametric flexible sensing platform. Adv Mater, 2016, 28: 138-143 CrossRef PubMed Google Scholar

[23] Lee D H, Heo G, Pyo K H. Mechanically robust and healable transparent electrode fabricated via vapor-assisted solution process. ACS Appl Mater Interfaces, 2016, 8: 8129-8136 CrossRef Google Scholar

[24] Pyo K H, Lee D H, Kim Y, et al. Extremely rapid and simple healing of a transparent conductor based on Ag nanowires and polyurethane with a diels-alder network. J Mater Chem, 2016, 4: 972--977. Google Scholar

[25] Hou C Y, Huang T, Wang H Z. A strong and stretchable self-healing film with self-activated pressure sensitivity for potential artificial skin applications. Sci Rep, 2013, 3: 3138 CrossRef PubMed ADS Google Scholar

[26] D'Elia E, Barg S, Ni N. Self-healing graphene-based composites with sensing capabilities. Adv Mater, 2015, 27: 4788-4794 CrossRef PubMed Google Scholar

[27] Guo K, Zhang D L, Zhang X M. Conductive elastomers with autonomic self-healing properties. Angew Chem Int Ed, 2015, 54: 12127-12133 CrossRef PubMed Google Scholar

[28] Zhang D L, Ju X, Li L H. An efficient multiple healing conductive composite via host-guest inclusion.. Chem Commun, 2015, 51: 6377-6380 CrossRef PubMed Google Scholar

[29] Williams K A, Boydston A J, Bielawski C W. Towards electrically conductive, self-healing materials. J R Soc Interface, 2007, 4: 359-362 CrossRef PubMed Google Scholar

[30] Aboudzadeh M A, Mu {n}oz M E, Santamar\'{\i}a A. Facile synthesis of supramolecular ionic polymers that combine unique rheological, ionic conductivity, and self-healing properties. Macromol Rapid Commun, 2012, 33: 314-318 CrossRef Google Scholar

[31] Feldner T, Haring M, Saha S. Supramolecular metallogel that imparts self-healing properties to other gel networks. Chem Mater, 2016, 28: 3210-3217 CrossRef Google Scholar

[32] Chen D, Wang D, Yang Y. Self-healing materials for next-generation energy harvesting and storage devices. Adv Energy Mater, 2017, 7: 1700890 CrossRef Google Scholar

[33] Blaiszik B J, Kramer S L B, Olugebefola S C. Self-healing polymers and composites. Annu Rev Mater Res, 2010, 40: 179-211 CrossRef ADS Google Scholar

[34] Chen X X. A thermally re-mendable cross-linked polymeric material. Science, 2002, 295: 1698-1702 CrossRef PubMed ADS Google Scholar

[35] Chen X X, Wudl F, Mal A K. New thermally remendable highly cross-linked polymeric materials. Macromolecules, 2003, 36: 1802-1807 CrossRef ADS Google Scholar

[36] Murphy E B, Bolanos E, Schaffner-Hamann C. Synthesis and characterization of a single-component thermally remendable polymer network: staudinger and stille revisited. Macromolecules, 2008, 41: 5203-5209 CrossRef ADS Google Scholar

[37] Park J S, Takahashi K, Guo Z H. Towards development of a self-healing composite using a mendable polymer and resistive heating. J Composite Mater, 2008, 42: 2869-2881 CrossRef Google Scholar

[38] Park J S, Kim H S, Thomas Hahn H. Healing behavior of a matrix crack on a carbon fiber/mendomer composite. Composites Sci Tech, 2009, 69: 1082-1087 CrossRef Google Scholar

[39] Peterson A M, Jensen R E, Palmese G R. Reversibly cross-linked polymer gels as healing agents for epoxy-amine thermosets. ACS Appl Mater Interfaces, 2009, 1: 992-995 CrossRef PubMed Google Scholar

[40] Otsuka H, Nagano S, Kobashi Y. A dynamic covalent polymer driven by disulfide metathesis under photoirradiation. Chem Commun, 2010, 46: 1150-1152 CrossRef PubMed Google Scholar

[41] Canadell J, Goossens H, Klumperman B. Self-healing materials based on disulfide links. Macromolecules, 2011, 44: 2536-2541 CrossRef ADS Google Scholar

[42] Amamoto Y, Otsuka H, Takahara A. Self-healing of covalently cross-linked polymers by reshuffling thiuram disulfide moieties in air under visible light. Adv Mater, 2012, 24: 3975-3980 CrossRef PubMed Google Scholar

[43] Deng G H, Tang C M, Li F Y. Covalent cross-linked polymer gels with reversible sol-gel transition and self-healing properties. Macromolecules, 2010, 43: 1191-1194 CrossRef ADS Google Scholar

[44] Kuhl N, Bode S, Bose R K. Acylhydrazones as reversible covalent crosslinkers for self-healing polymers. Adv Funct Mater, 2015, 25: 3295-3301 CrossRef Google Scholar

[45] Whiteley J M, Taynton P, Zhang W. Ultra-thin solid-state li-ion electrolyte membrane facilitated by a self-healing polymer matrix. Adv Mater, 2015, 27: 6922-6927 CrossRef PubMed Google Scholar

[46] Taynton P, Ni H G, Zhu C P. Repairable woven carbon fiber composites with full recyclability enabled by malleable polyimine networks. Adv Mater, 2016, 28: 2904-2909 CrossRef PubMed Google Scholar

[47] Lu Y X, Guan Z B. Olefin metathesis for effective polymer healing via dynamic exchange of strong carbon-carbon double bonds. J Am Chem Soc, 2012, 134: 14226-14231 CrossRef PubMed Google Scholar

[48] Campanella A, Dohler D, Binder W H. Self-healing in supramolecular polymers. Macromol Rapid Commun, 2018: 1700739. Google Scholar

[49] Herbst F, Dohler D, Michael P. Self-healing polymers via supramolecular forces.. Macromol Rapid Commun, 2013, 34: 203-220 CrossRef PubMed Google Scholar

[50] Cordier P, Tournilhac F, Soulié-Ziakovic C. Self-healing and thermoreversible rubber from supramolecular assembly. Nature, 2008, 451: 977-980 CrossRef PubMed ADS Google Scholar

[51] Montarnal D, Tournilhac F, Hidalgo M. Versatile one-pot synthesis of supramolecular plastics and self-healing rubbers.. J Am Chem Soc, 2009, 131: 7966-7967 CrossRef PubMed Google Scholar

[52] Yang L, Lin Y L, Wang L S. The synthesis and characterization of supramolecular elastomers based on linear carboxyl-terminated polydimethylsiloxane oligomers. Polym Chem, 2014, 5: 153-160 CrossRef Google Scholar

[53] Zhang A Q, Yang L, Lin Y L. Self-healing supramolecular elastomers based on the multi-hydrogen bonding of low-molecular polydimethylsiloxanes: synthesis and characterization. J Appl Polym Sci, 2013, 129: 2435-2442 CrossRef Google Scholar

[54] Maes F, Montarnal D, Cantournet S. Activation and deactivation of self-healing in supramolecular rubbers. Soft Matter, 2012, 8: 1681-1687 CrossRef ADS Google Scholar

[55] White S R, Sottos N R, Geubelle P H. Autonomic healing of polymer composites. Nature, 2001, 409: 794-797 CrossRef PubMed Google Scholar

[56] Rule J D, Brown E N, Sottos N R. Wax-protected catalyst microspheres for efficient self-healing materials. Adv Mater, 2005, 17: 205-208 CrossRef Google Scholar

[57] Jackson A C, Bartelt J A, Marczewski K. Silica-protected micron and sub-micron capsules and particles for self-healing at the microscale. Macromol Rapid Commun, 2011, 32: 82-87 CrossRef PubMed Google Scholar

[58] Yuan Y C, Rong M Z, Zhang M Q. Study of factors related to performance improvement of self-healing epoxy based on dual encapsulated healant. Polymer, 2009, 50: 5771-5781 CrossRef Google Scholar

[59] Cho S H, Andersson H M, White S R. Polydimethylsiloxane-based self-healing materials. Adv Mater, 2006, 18: 997-1000 CrossRef Google Scholar

[60] Caruso M M, Delafuente D A, Ho V. Solvent-promoted self-healing epoxy materials. Macromolecules, 2007, 40: 8830-8832 CrossRef ADS Google Scholar

[61] Yang J L, Keller M W, Moore J S. Microencapsulation of isocyanates for self-healing polymers. Macromolecules, 2008, 41: 9650-9655 CrossRef ADS Google Scholar

[62] Bleay S M, Loader C B, Hawyes V J. A smart repair system for polymer matrix composites. Composites Part A-Appl Sci Manufacturing, 2001, 32: 1767-1776 CrossRef Google Scholar

[63] Pang J W C, Bond I P. A hollow fibre reinforced polymer composite encompassing self-healing and enhanced damage visibility. Composites Sci Tech, 2005, 65: 1791-1799 CrossRef Google Scholar

[64] Williams H R, Trask R S, Bond I P. Self-healing composite sandwich structures. Smart Mater Struct, 2007, 16: 1198-1207 CrossRef ADS Google Scholar

[65] Toohey K S, Sottos N R, Lewis J A. Self-healing materials with microvascular networks. Nat Mater, 2007, 6: 581-585 CrossRef PubMed Google Scholar

[66] So J H, Thelen J, Qusba A. Reversibly deformable and mechanically tunable fluidic antennas. Adv Funct Mater, 2009, 19: 3632-3637 CrossRef Google Scholar

[67] Blaiszik B J, Kramer S L B, Grady M E. Autonomic restoration of electrical conductivity. Adv Mater, 2012, 24: 398-401 CrossRef PubMed Google Scholar

[68] Odom S A, Chayanupatkul S, Blaiszik B J. A self-healing conductive ink. Adv Mater, 2012, 24: 2578-2581 CrossRef PubMed Google Scholar

[69] Kang S, Jones A R, Moore J S. Microencapsulated carbon black suspensions for restoration of electrical conductivity. Adv Funct Mater, 2014, 24: 2947-2956 CrossRef Google Scholar

[70] Caruso M M, Schelkopf S R, Jackson A C. Microcapsules containing suspensions of carbon nanotubes. J Mater Chem, 2009, 19: 6093-6096 CrossRef Google Scholar

[71] Sun H, You X, Jiang Y. Self-healable electrically conducting wires for wearable microelectronics.. Angew Chem Int Ed, 2014, 53: 9526-9531 CrossRef PubMed Google Scholar

[72] Zhang X Y, Tang Z, Tian D. A self-healing flexible transparent conductor made of copper nanowires and polyurethane. Mater Res Bull, 2017, 90: 175-181 CrossRef Google Scholar

[73] Sun J Y, Keplinger C, Whitesides G M. Ionic skin. Adv Mater, 2014, 26: 7608-7614 CrossRef PubMed Google Scholar

[74] Kim C C, Lee H H, Oh K H. Highly stretchable, transparent ionic touch panel. Science, 2016, 353: 682-687 CrossRef PubMed ADS Google Scholar

[75] Wang J, Liu F, Tao F. Rationally Designed Self-Healing Hydrogel Electrolyte toward a Smart and Sustainable Supercapacitor. ACS Appl Mater Interfaces, 2017, 9: 27745-27753 CrossRef Google Scholar

[76] Cheng X, Pan J, Zhao Y. Gel polymer electrolytes for electrochemical energy storage. Adv Energy Mater, 2018, 8: 1702184 CrossRef Google Scholar

[77] Guo Y, Zheng K, Wan P. A flexible stretchable hydrogel electrolyte for healable all-in-one configured supercapacitors. Small, 2018, 14: 1704497 CrossRef PubMed Google Scholar

[78] Cai G, Wang J, Qian K. Extremely stretchable strain sensors based on conductive self-healing dynamic cross-links hydrogels for human-motion detection. Adv Sci, 2017, 4: 1600190 CrossRef PubMed Google Scholar

[79] Liu S, Lin Y, Wei Y. A high performance self-healing strain sensor with synergetic networks of poly($\varepsilon$-caprolactone) microspheres, graphene and silver nanowires. Composites Sci Tech, 2017, 146: 110-118 CrossRef Google Scholar

[80] Han Y Y, Wu X D, Zhang X X. Self-healing, highly sensitive electronic sensors enabled by metal-ligand coordination and hierarchical structure design. ACS Appl Mater Interfaces, 2017, 9: 20106-20114 CrossRef Google Scholar

[81] Liu X, Lu C, Wu X. Self-healing strain sensors based on nanostructured supramolecular conductive elastomers. J Mater Chem A, 2017, 5: 9824-9832 CrossRef Google Scholar

[82] Cao J, Zhang X, Lu C. Self-healing sensors based on dual noncovalent network elastomer for human motion monitoring. Macromol Rapid Commun, 2017, 38: 1700406 CrossRef PubMed Google Scholar

[83] Cao J, Lu C, Zhuang J. Multiple Hydrogen Bonding Enables the Self-Healing of Sensors for Human-Machine Interactions.. Angew Chem Int Ed, 2017, 56: 8795-8800 CrossRef PubMed Google Scholar

[84] Hou J, Liu M, Zhang H. Healable green hydrogen bonded networks for circuit repair, wearable sensor and flexible electronic devices. J Mater Chem A, 2017, 5: 13138-13144 CrossRef Google Scholar

[85] Rong Q, Lei W, Chen L. Anti-freezing, conductive self-healing organohydrogels with stable strain-sensitivity at subzero temperatures. Angew Chem Int Ed, 2017, 56: 14159-14163 CrossRef PubMed Google Scholar

[86] Liu Y J, Cao W T, Ma M G. Ultrasensitive wearable soft strain sensors of conductive, self-healing, and elastic hydrogels with synergistic “soft and hard" hybrid networks. ACS Appl Mater Interfaces, 2017, 9: 25559-25570 CrossRef Google Scholar

[87] Liu S, Li L. Ultrastretchable and self-healing double-network hydrogel for 3d printing and strain sensor. ACS Appl Mater Interfaces, 2017, 9: 26429-26437 CrossRef Google Scholar

[88] Liu S, Li K, Hussain I. A Conductive Self-Healing Double Network Hydrogel with Toughness and Force Sensitivity.. Chem Eur J, 2018, 24: 6632-6638 CrossRef PubMed Google Scholar

[89] Wang T, Zhang Y, Liu Q. A self-healable, highly stretchable, and solution processable conductive polymer composite for ultrasensitive strain and pressure sensing. Adv Funct Mater, 2018, 28: 1705551 CrossRef Google Scholar

[90] Li J, Liu Q, Ho D. Three-dimensional graphene structure for healable flexible electronics based on diels-alder chemistry. ACS Appl Mater Interfaces, 2018, 10: 9727-9735 CrossRef Google Scholar

[91] Yang H, Qi D, Liu Z. Soft thermal sensor with mechanical adaptability. Adv Mater, 2016, 28: 9175-9181 CrossRef PubMed Google Scholar

[92] Zhang Q, Liu L, Pan C. Thermally sensitive, adhesive, injectable, multiwalled carbon nanotube covalently reinforced polymer conductors with self-healing capabilities. J Mater Chem C, 2018, 6: 1746-1752 CrossRef Google Scholar

[93] Fowler J D, Allen M J, Tung V C. Practical chemical sensors from chemically derived graphene. ACS Nano, 2009, 3: 301-306 CrossRef PubMed Google Scholar

[94] Wang S, Xu L P, Zhang X. Ultrasensitive electrochemical biosensor based on noble metal nanomaterials. Sci Adv Mater, 2015, 7: 2084-2102 CrossRef Google Scholar

[95] Bandodkar A J, Jeerapan I, Wang J. Wearable chemical sensors: present challenges and future prospects. ACS Sens, 2016, 1: 464-482 CrossRef Google Scholar

[96] Gao W, Emaminejad S, Nyein H Y Y. Fully integrated wearable sensor arrays for multiplexed in situ perspiration analysis. Nature, 2016, 529: 509-514 CrossRef PubMed ADS Google Scholar

[97] Huang W, Besar K, Zhang Y. A high-capacitance salt-free dielectric for self-healable, printable, and flexible organic field effect transistors and chemical sensor. Adv Funct Mater, 2015, 25: 3745-3755 CrossRef PubMed Google Scholar

[98] Jin H, Huynh T P, Haick H. Self-healable sensors based nanoparticles for detecting physiological markers via skin and breath: toward disease prevention via wearable devices. Nano Lett, 2016, 16: 4194-4202 CrossRef PubMed ADS Google Scholar

[99] Huynh T P, Khatib M, Srour R. Composites of polymer and carbon nanostructures for self-healing chemical sensors. Adv Mater Technol, 2016, 1: 1600187 CrossRef Google Scholar

[100] Fan Z, Ho J C, Takahashi T. Toward the development of printable nanowire electronics and sensors. Adv Mater, 2009, 21: 3730-3743 CrossRef Google Scholar

[101] Fukuda K, Takeda Y, Yoshimura Y. Fully-printed high-performance organic thin-film transistors and circuitry on one-micron-thick polymer films. Nat Commun, 2014, 5: 4147 CrossRef PubMed ADS Google Scholar

[102] Lu C C, Lin Y C, Yeh C H. High mobility flexible graphene field-effect transistors with self-healing gate dielectrics. ACS Nano, 2012, 6: 4469-4474 CrossRef PubMed Google Scholar

[103] Ko J, Kim Y J, Kim Y S. Self-healing polymer dielectric for a high capacitance gate insulator. ACS Appl Mater Interfaces, 2016, 8: 23854-23861 CrossRef Google Scholar

[104] Bauer S. Flexible electronics: Sophisticated skin. Nat Mater, 2013, 12: 871-872 CrossRef PubMed ADS Google Scholar

[105] Choi S, Lee H, Ghaffari R. Recent advances in flexible and stretchable bio-electronic devices integrated with nanomaterials. Adv Mater, 2016, 28: 4203-4218 CrossRef PubMed Google Scholar

[106] Hammock M L, Chortos A, Tee B C K. 25th anniversary article: The evolution of electronic skin (e-skin): a brief history, design considerations, and recent progress. Adv Mater, 2013, 25: 5997-6038 CrossRef PubMed Google Scholar

[107] Kim D H, Lu N, Ma R. Epidermal electronics. Science, 2011, 333: 838-843 CrossRef PubMed ADS Google Scholar

[108] Kuang X, Chen K, Dunn C K. 3D printing of highly stretchable, shape-memory, and self-healing elastomer toward novel 4D printing. ACS Appl Mater Interfaces, 2018, 10: 7381-7388 CrossRef Google Scholar

[109] Yu Y, Liu F, Zhang R. Suspension 3D printing of liquid metal into self-healing hydrogel. Adv Mater Technol, 2017, 2: 1700173 CrossRef Google Scholar

  • Click to view Download high-quality image

    Figure 1

    (Color online) Schematic of self-healing mechanism of polymers [32]@Copyright 2017 John Wiley and Sons. protectłinebreak(a) Intrinsic; (b) extrinsic

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    Figure 2

    (Color online) Schematic of self-healing of conductive material/polymer composites: (a) Schematic of self-healing via embedding liquid conductive materials capsules [67]@Copyright 2011 John Wiley and Sons. (b) Schematic of self-healing of AgNWs/(bPEI/PAA-HA) composite with the aid of water [19]@Copyright 2012 John Wiley and Sons. (c) Schematic of the microstructure of $\mu$Ni/L composite and the process of electrical self-healing. 1. Undamaged material; 2. completely fractured material; 3. Self-supporting material with its fractured surfaces contact for 15 s; 4. Flexed material after being healed for 5 min, showing its mechanical strength and flexibility [14]@Copyright 2012 Springer Nature

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    Figure 3

    (Color online) Self-healing piezoresistive force sensor based on $\mu$Ni/L composite [14]@Copyright 2012 Springer Nature. (a) Current-voltage curve of a commercial LED using self-healing $\mu$Ni/L composite as conducting wire. Inset: optical photograph of the circuit taken at 2.5 V (scale bar, 10 mm). (b) and (c) Self-healing of the (b) electrical and (c) mechanicalperformance of $\mu$Ni/L composite. (d) Electrical response of the flexion sensors based on $\mu$Ni/L composite in free-standing modes and self-adhered modes on PET substrate. (e) Electrical response of the parallel-plate structured tactile sensor based on $\mu$Ni/L composite. (f) Self-healing flexion and tactile sensor circuit schematic and the optical photograph of a fully articulated wooden mannequin with its elbow and palm region mounted with the flexion and tactile sensor circuits

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    Figure 4

    (Color online) Real-time monitoring of human motions using the superelastic strain sensor based on self-healing SWNT/PVA-borax hydrogel composite [78]. (a) Bending and release of the finger; (b) bending of the knee; (c) bending and release of the neck; (d) bending and release of the elbow

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    Figure 5

    (Color online) Self-healing piezoresistive stress/strain sensor based on conductive polymer [15]@Copyright 2017 John Wiley and Sons. (a) Schematic of the self-healing mechanism; (b) self-healing efficiency of mechanical property; protectłinebreak(c) electrical self-healing property; (d) schematic of the preparation of wearable sensor via 3D printing technique; protectłinebreak (e) real-time human motion monitoring system based on the wearable sensor and smart phone

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    Figure 6

    (Color online) SWNT/L composite [91]@Copyright 2016 John Wiley and Sons. (a) Schematic of the structure; (b) and (c) optical photographs; (d) and (e) temperature sensing performance and the optical photographs showing the measurement procedure; (f) electrical self-healing performance

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    Figure 7

    (Color online) Self-healable flexible gas sensor based on MWNT/PEM composite film [21]@Copyright 2015 John Wiley and Sons. (a) Schematic showing the self-healing procedure of the gas sensor; (b)–(e) SEM images of MWNT/PEM film with a cut before and after being healed; (f) electrical self-healing property; (g) the sensing sensitivity of MWNT/PEM film to 25 ppm ${\rm~NH}_{3}$ after healing for different times

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    Figure 8

    (Color online) Self-healing flexible multifunctional sensor [22]@Copyright 2015 John Wiley and Sons. protectłinebreak(a) Schematic of the device structure and its optical photograph; SEM images of the microstructure of (b1)–(b4) PU substrate, (c1)–(c4) PU/$\mu$Ag composite, and (d1)–(d4) AuNP film with a cut showing the self-healing procedure; (e) electrical response to bending deformation; (f) electrical response to stretching deformation; (g) electrical response to VOC n-octanol; (h) electrical response to temperature variation

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    Figure 9

    (Color online) The overall experimental strategy relating to the flexible self-healable multifunctional sensor for human health monitoring application [98]@Copyright 2016 American Chemical Society. (a) Schematic of the structure; protectłinebreak(b) schematic of the molecular structure used for the functionalization of AuNP; (c) demonstration of the self-heal of the sensor under 3 different damage modes

  • Table 1   Summary of the self-healing performance of typical polymers $^{\rm~a)}$
    Material Mechanical Healing Healing Healing Ref.
    strength mechanism condition efficiency (%
    3M4F 121 MPa/ Thermal reversible 120${^\circ}$C$\sim$150${^\circ}$C 41$\sim$50 [34]
    Compression DA reaction (N$_{2})$/2 h$~\to~$RT
    2MEP4F 121 MPa/ Thermal reversible 115${^\circ}$C/30 min 80 [35]
    Compression DA reaction $\to~$40${^\circ}$C/6 h
    DCPD based 85 MPa/par Compression Thermal reversible 120${^\circ}$C(Ar)/20 h 46 [36]
    polymer DA reaction
    Epoxy based par rubber 0.5 MPa/par Stretch Disulfide bond 60${^\circ}$C/1 h 95 [41]
    PU rubber 3.9 MPa/par Stretch Disulfide bond Visible light/ 24 h 97 [42]
    Ru/PBD 0.4 MPa/par Stretch C-C double bond 20 kPa/1 h 100 [47]
    CF/polyimine 140 MPa/par Bending Imine bond 121${^\circ}$C/45 MPa 100 [46]
    M1-TEGMEMA – Acylhydrazone bond 100${^\circ}$C/24 h 100 [44]
    Fatty acid based SR 2 MPa/par Stretch Hydrogen bond RT/3 h 100 [50]
    PDMS-COOH$_{2}$ par based SR 0.4 MPa/par Stretch Hydrogen bond 80${^\circ}$C/16 h 100 [53]

    a) 3M (maleimide monomor); 4F (furan monomer); RT (room temperature); 2MEP (1, 8-Bis(maleimido)-1-ethylpropane); DCPD (dicyclopentadiene); PU (polyurethane); PBD (polybutadiene); CF (carbon fiber); M1 (acylhydrazone monomer); TEGMEMA (triethylene glycol methylether methacrylate); SR (supermolecular rubber); PDMS (polydimethylsiloxane oligomers); COOH (carboxyl)

  • Table 2   Summary of typical research about flexible self-healing sensors$^{\rm~a)}$
    Material Healing par mechanism Healing condition/par efficiency Application Ref.
    MDPB-TDF/ S-CCTO Self-healing of SWNT 105${^\circ}$C/30 min: Capacitive [13]
    driven by thermal electrical$\sim~$89%; force sensor
    reversible DA reaction mechanical$\sim~$86%
    $\mu~$Ni/L Hydrogen bond 50 kPa/15 s: electrical$\sim~$90% Piezoresistive [14]
    50${^\circ}$C/10 min: mechanical$\sim~$100% force sensor
    rGO/PBS B-O dative bond & RT/10 min: par electrical$\sim~$90%; Piezoresistive [26]
    hydrogen bond mechanical$\sim~$80% force sensor
    SWNT/ PVA-borax Hydrogen bond RT/3.2 s: electrical$\sim~$98% Piezoresistive [78]
    force sensor
    m-PCL/GO/ AgNWs Hydrogen bond 80${^\circ}$C/3 min: par electrical$\sim~$80%; Piezoresistive [79]
    mechanical$\sim~$100% force sensor
    CNT-Fe$^{3~+~}$/PDA@ENR Metal coordination bond RT/24 h: par electrical$\sim~$100%; Piezoresistive [80]
    mechanical$\sim~$89.3% force sensor
    CNTs@(PEI@CNC)/ Hydrogen bond Hot-press: par electrical$\sim~$100%; piezoresistive [81]
    XNBR mechanical$\sim~$83% force sensor
    C-CNC@GA@Ca$^{2+}$ Hydrogen & RT/30 s: par electrical$\sim~$100%; Piezoresistive [82]
    @CNTs/ENR metal coordination bond mechanical$\sim~$90% force sensor
    C-CNC@CT@CNTs/ENR Hydrogen bond RT/15 s: par electrical$\sim~$100%; Piezoresistive par [83]
    mechanical$\sim~$100% force sensor
    Amylopectin par hydrogel Hydrogen bond RT/3 s: electrical$\sim~$99.3%; Piezoresistive [84]
    RT/5 min: mechanical$\sim~$98.4% force sensor
    PVA-PEDOT: PSS Hydrogen bond 80${^\circ}$C $\to~-$20${^\circ}$C: par electrical$\sim~$100%; Piezoresistive [85]
    mechanical$\sim~$85% force sensor
    PVA-PVP/CNC-Fe$^{3~+~}$ Ionic coordination bond RT/5 min: par electrical$\sim~$100%; Piezoresistive [86]
    mechanical$\sim~$100% force sensor
    $\kappa~$-carrageenan/PAAm Thermal-reversibleg 90${^\circ}$C/20 min: par electrical$\sim~$99.2%; Piezoresistive [87]
    $\kappa~$-carrageenan mechanical$\sim~$100% force sensor
    PEG-PAA Metal coordination & RT/2 h: electrical $\sim~$100% par RT/12 h: Piezoresistive [88]
    Hydrogen bond mechanical$\sim~$96.8% force sensor
    PANI-PAA-PA Hydrogen bond & Slight pressure/24 h: electrical$\sim~$99%; Piezoresistive [89]
    electrostatic interaction mechanical$\sim~$99% force sensor
    Graphene/PU Thermal reversible Microwave/5 min$~\to~$65${^\circ}$C/5 h: par Piezoresistive [90]
    DA reaction electrical$\sim~$75%; mechanical$\sim~$100% force sensor
    PAA-Fe$^{3~+~}$/DCh-PPy Ionic interaction RT/1 min: electrical$\sim~$96% par Piezoresistive [15]
    RT/2 min: mechanical$\sim~$100% force sensor
    PDMAA-PVA/rGO Hydrogen bond RT/12 h: par electrical$\sim~$89.6%; Piezoresistive [25]
    mechanical$\sim~$100% force sensor
    SWNT/L Hydrogen bond RT/1 h: electrical$\sim~$100% Temperature sensor [91]
    P(BMA-co-LMA)/MWNT C-C double cond 60${^\circ}$C/3 h: par electrical$\sim~$98%; Temperature sensor [92]
    mechanical$\sim~$94%
    MWNT/PEM Hydrogen bond & Water/30 min: par electrical $\sim~$91%; Gas sensor [21]
    electrostatic interaction mechanical$\sim~$100%

    a) S-CCTO (surface-modified CaCu3Ti4O12); MDPB (1, 1'-(methylene di-4, 1-phenylene) bismaleimide); TDF (2, 2'-(Thiodimethylene) difuran); PBS (polyborosiloxane); PVA (polyvinyl alcohol); m-PCL (poly( 3-caprolactone) microspheres); PDA (polydopamine); ENR (epoxidized natural rubber); PEI (polyethyleneimine); C-CNC (carboxyl cellulose nanocrystals); XNBR (carboxylated nitrile rubber); GA (gelatin); CT (chitosan); PEDOT:PSS (poly(3, 4-ethylenedioxythiophene):polystryrene sulfonate); PVP (polyvinyl pyrrolidone); PAAm (polyacrylamide); PEG (polyethylene glycol); PAA (poly(acrylic acid)); PANI (polyaniline); PA (phytic acid); DCh (double-bond decorated chitosan); PPy (polypyrrole); PDMAA (poly(N, N-dimethylacrylamide)); P(BMA-co-LMA) (poly(butyl methacrylate-co-lauryl methacrylate)); PEM (polyelectrolyte multilayer)