Polymer ionogels and their application in flexible ionic devices

Abstract

Polymer ionogel (PIG) is a new type of flexible, stretchable, and ion-conductive material, which generally consists of two components (polymer matrix materials and ionic liquids/deep eutectic solvents). More and more attention has been received owing to its excellent properties, such as nonvolatility, good ionic conductivity, excellent thermal stability, high electrochemical stability, and transparency. In this review, the latest research and developments of PIGs are comprehensively reviewed according to different polymer matrices. Particularly, the development of novel structural designs, preparation methods, basic properties, and their advantages are respectively summarized. Furthermore, the typical applications of PIGs in flexible ionic skin, flexible electrochromic devices, flexible actuators, and flexible power supplies are reviewed. The novel working mechanism, device structure design strategies, and the unique functions of the PIG-based flexible ionic devices are briefly introduced. Finally, the perspectives on the current challenges and future directions of PIGs and their application are discussed.

Keywords

electrochromism device / flexible ionic devices / flexible ionic skin / ionic liquid / ionogel

References

[1] Wang Z, Chen Z, Wang J, Shangguan L, Fan S, Duan Y. Realization of an autonomously controllable process for atomic layer deposition and its encapsulation application in flexible organic light-emitting diodes. Opt Express. 2023;31(13):21672-21688.

[2] Zhang Z, Wang W, Jiang Y, et al. High-brightness all-polymer stretchable LED with charge-trapping dilution. Nature. 2022;603:624-630.

[3] Wang L, Zhang T, Shen J, et al. Flexibly photo-regulated brain-inspired functions in flexible neuromorphic transistors. ACS Appl Mater Interfaces. 2023;15:13380-13392.

[4] Song J, Liu H, Zhao Z, Lin P, Yan F. Flexible organic transistors for biosensing: devices and applications. Adv Mater. 2023;35:2300034.

[5] Hu B, Sun H, Tian J, et al. Advances in flexible graphene field-effect transistors for biomolecule sensing. Front Bioeng Biotechnol. 2023;11:1218024.

[6] Pan X, Wang Q, Guo R, et al. An adaptive ionic skin with multiple stimulus responses and moist-electric generation ability. J Mater Chem A. 2020;8:17498-17506.

[7] Wang H, Wang Z, Yang J, Xu C, Zhang Q, Peng Z. Ionic gels and their applications in stretchable electronics. Macromol Rapid Commun. 2018;39:1800246.

[8] Liang Y, Qiao L, Qiao B, Guo B. Conductive hydrogels for tissue repair. Chem Sci. 2023;14:3091-3116.

[9] Ding Y, Sun H, Li Z, et al. Galvanic-driven deposition of large-area Prussian blue films for flexible battery-type electrochromic devices. J Mater Chem A. 2023;11:2868-2875.

[10] Vinh Quy VH, Kim KW, Yeo J, et al. Tunable electrochromic behavior of biphenyl poly(viologen)-based ion gels in all-in-one devices. Org Electron. 2022;100:106395.

[11] Parashar RK, Kandpal S, Bandyopadhyay P, Sadhukhan M, Kumar R, Mondal PC. Flexible molecular electrochromic devices run by low-cost commercial cells. Adv Opt Mater. 2023;11:2202920.

[12] Gong H, Li A, Fu G, et al. Ultrathin flexible electrochromic devices enabled by highly transparent ion-conducting films. J Mater Chem A. 2023;11:8939-8949.

[13] Pang W, Xu S, Liu L, Bo R, Zhang Y. Thin-film-shaped flexible actuators. Adv Intell Syst. 2023;5:2300060.

[14] Ahn J, Gu J, Choi J, et al. A review of recent advances in electrically driven polymer-based flexible actuators: smart materials structures and their applications. Adv Mater Technol. 2022;7:2200041.

[15] Zhou H, Lai J, Zheng B, et al. From glutinous-rice-inspired adhesive organohydrogels to flexible electronic devices toward wearable sensing power supply and energy storage. Adv Funct Mater. 2021;32:2108423.

[16] Wu Y, Luo Y, Cuthbert TJ, et al. Hydrogels as soft ionic conductors in flexible and wearable triboelectric nanogenerators. Adv Sci. 2022;9(11):2106008.

[17] Chen L, Zhao C, Duan X, Zhou J, Liu M. Finely tuning the lower critical solution temperature of ionogels by regulating the polarity of polymer networks and ionic liquids. CCS Chem. 2022;4:1386-1396.

[18] Wang S, Bai M, Liu C, et al. Highly stretchable multifunctional polymer ionic conductor with high conductivity based on organic-inorganic dual networks. Chem Eng J. 2022;440:135824.

[19] Lee HC, Kim MJ, Kim MH, et al. Dual-supporter and dual-salt strategy for solid polymer electrolyte with high ionic conductivity and elastic toughness. Adv Electron Mater. 2023;9:2300094.

[20] Fu D, Sun Y, Zhang F, et al. Enabling polymeric ionic liquid electrolytes with high ambient ionic conductivity by polymer chain regulation. Chem Eng J. 2022;431:133278.

[21] Qin S, Cao Y, Zhang J, et al. Polymer dispersed ionic liquid electrolytes with high ionic conductivity for ultrastable solid-state lithium batteries. Carbon Energy. 2023;5:316.

[22] Ran Y, Lu D, Jiang J, Huang Y, Wang W, Cao J. Deep eutectic solvents-assisted wood densification: a promising strategy for shape-fixation. Chem Eng J. 2023;471:144476.

[23] Liu R, Qiao C, Liu Q, Liu L, Yao J. Fabrication and properties of anti-freezing gelatin hydrogels based on a deep eutectic solvent. ACS Appl Polym Mater. 2023;5:4546-4553.

[24] Zhu A, Xu Q, Huang J, et al. Fabrication of gelatin-derived gel electrolyte using deep eutectic solvents through in situ derivatization and crosslinking strategy for supercapacitors and flexible sensors. ACS Appl Mater Interfaces. 2023;15(35):41483-41493.

[25] Wasserscheid P, Keim W. Ionic liquids-new “solutions” for transition metal catalysis. Angew Chem. 2000;39:3772-3789.

[26] Liao M, Wan P, Wen J, et al. Wearable healable and adhesive epidermal sensors assembled from mussel-inspired conductive hybrid hydrogel framework. Adv Funct Mater. 2017;27:1703852.

[27] Gale PA, Davis JT, Quesada R. Anion transport and supramolecular medicinal chemistry. Chem Soc Rev. 2017;46:2497-2519.

[28] Liu G, Ding X, Cao Y, Zheng Z, Peng Y. Novel shape-memory polymer with two transition temperatures. Macromol Rapid Commun. 2005;26:649-652.

[29] Zhang J, Yuan H, Li L, et al. Hydrogel from chrome shavings as a sustainable highly sensitive ionic skin for pressure sensing. ACS Sustain Chem Eng. 2022;10:8172-8183.

[30] Han S, Zhang R, Han L, Zhao C, Yan X, Dai M. An antifatigue and self-healable ionic polyurethane/ionic liquid composite as the channel layer for a low energy cost synaptic transistor. Eur Polym J. 2022;174:111292.

[31] Carpio P, Bannier E, Salvador MD, Borrell A, Moreno R, Sánchez E. Effect of particle size distribution of suspension feedstock on the microstructure and mechanical properties of suspension plasma spraying YSZ coatings. Surf Coat Technol. 2015;268:293-297.

[32] Brändler L, Niklaus L, Schott M, Löbmann P. Photochemical precharging of tungsten trioxide for enhanced transmittance modulation in flexible electrochromic devices. Adv Mater Technol. 2023;8:2201903.

[33] Wang Z, Hang G, Li J, Wang Y, Xiao K. A micro-robot fish with embedded SMA wire actuated flexible biomimetic fin. Sens Actuators, A. 2008;144:354-360.

[34] Kosidlo U, Omastová M, Micusík M, et al. Nanocarbon based ionic actuators—a review. Smart Mater Struct. 2013;22:104022.

[35] Yuan Y, Zhou J, Lu G, Sun J, Tang L. Highly stretchable transparent and self-adhesive ionic conductor for high-performance flexible sensors. ACS Appl Polym Mater. 2021;3:1610-1617.

[36] Sun J, Yuan Y, Lu G, Li L, Zhu X, Nie J. A transparent stretchable stable self-adhesive ionogel-based strain sensor for human motion monitoring. J Mater Chem C. 2019;7:11244-11250.

[37] Kim YM, Moon HC. Ionoskins: nonvolatile highly transparent ultrastretchable ionic sensory platforms for wearable electronics. Adv Funct Mater. 2019;30:1907290.

[38] Wang M, Zhang P, Shamsi M, et al. Tough and stretchable ionogels by in situ phase separation. Nat Mater. 2022;21:359-365.

[39] Lei Z, Wu P. A highly transparent and ultra-stretchable conductor with stable conductivity during large deformation. Nat Commun. 2019;10:3429.

[40] Bu X, Ge Y, Wang L, Wu L, Ma X, Lu D. Design of highly stretchable deep eutectic solvent-based ionic gel electrolyte with high ionic conductivity by the addition of zwitterion ion dissociators for flexible supercapacitor. Polym Eng Sci. 2020;61:154-166.

[41] Li S, Chen Y, Zhu Y, Wang Z, Fu J, Yan S. Rapid preparation of conductive and self-healing ionic gels with tunable mechanical properties via frontal polymerization of deep eutectic monomers. Colloid Polym Sci. 2022;300:989-998.

[42] Yao P, Bao Q, Yao Y, et al. Environmentally stable robust adhesive and conductive supramolecular deep eutectic gels as ultrasensitive flexible temperature sensor. Adv Mater. 2023;35:2300114.

[43] Lan J, Li Y, Yan B, Yin C, Ran R, Shi LY. Transparent stretchable dual-network ionogel with temperature tolerance for high-performance flexible strain sensors. ACS Appl Mater Interfaces. 2020;12:37597-37606.

[44] Tang Z, Lyu X, Xiao A, Shen Z, Fan X. High-performance double-network ion gels with fast thermal healing capability via dynamic covalent bonds. Chem Mater. 2018;30:7752-7759.

[45] Li WH, Lin KB, Chen L, Yang DS, Ge Q, Wang ZL. Self-powered wireless flexible ionogel wearable devices. ACS Appl Mater Interfaces. 2023;15:14768-14776.

[46] Wang S, Zhang D, He X, et al. Polyzwitterionic double-network ionogel electrolytes for supercapacitors with cryogenic-effective stability. Chem Eng J. 2022;438:135607.

[47] Ren Y, Guo J, Liu Z, et al. Ionic liquid-based click-ionogels. Sci Adv. 2019;5:eaax0648.

[48] Kamio E, Yasui T, Iida Y, Gong JP, Matsuyama H. Inorganic/organic double-network gels containing ionic liquids. Adv Mater. 2017;29:1704118.

[49] Wu Q, Han S, Zhu J, et al. Stretchable and self-healing ionic conductive elastomer for multifunctional 3D printable sensor. Chem Eng J. 2023;454:140328.

[50] Zhu M, He S, Dai Y, et al. Long-lasting sustainable self-healing ion gel with triple-network by trigger-free dynamic hydrogen bonds and ion bonds. ACS Sustain Chem Eng. 2018;6:17087-17098.

[51] Wu Y, Jiang W, Zhang X, et al. Highly conductive transparent adhesive and self-healable ionogel based on a deep eutectic solvent with widely adjustable mechanical strength. Macromol Rapid Commun. 2022;43:2200480.

[52] Xie F, Gao X, Yu Y, Lu F, Zheng L. Dually cross-linked single network poly(ionic liquid)/ionic liquid ionogels for a flexible strain-humidity bimodal sensor. Soft Matter. 2021;17:10918-10925.

[53] Płotka-Wasylka J, de la Guardia M, Andruch V, Vilková M. Deep eutectic solvents vs ionic liquids: similarities and differences. Microchem J. 2020;159:105539.

[54] Zhang Y, Wang Y, Guan Y, Zhang Y. Peptide-enhanced tough resilient and adhesive eutectogels for highly reliable strain/pressure sensing under extreme conditions. Nat Commun. 2022;13:6671.

[55] Wang J, Ma Z, Wang Y, Shao J, Yan L. Ultra-stretchable self-healing conductive and transparent PAA/DES ionic gel. Macromol Rapid Commun. 2021;42:2000445.

[56] Wang J, Deng Y, Ma Z, Wang Y, Zhang S, Yan L. Lignin promoted the fast formation of a robust and highly conductive deep eutectic solvent ionic gel at room temperature for a flexible quasi-solid-state supercapacitor and strain sensors. Green Chem. 2021;23:5120-5128.

[57] Wang M, Lai Z, Jin X, Sun T, Liu H, Qi H. Multifunctional liquid-free ionic conductive elastomer fabricated by liquid metal induced polymerization. Adv Funct Mater. 2021;31:2101957.

[58] Li R, Fan T, Chen G, et al. Autonomous self-healing antifreezing and transparent conductive elastomers. Chem Mater. 2020;32:874-881.

[59] Li R, Zhang K, Chen G, Su B, He M. Stiff self-healable transparent polymers with synergetic hydrogen bonding interactions. Chem Mater. 2021;33:5189-5196.

[60] Gong JP, Katsuyama Y, Kurokawa T, Osada Y. Double-network hydrogels with extremely high mechanical strength. Adv Mater. 2003;15:1155-1158.

[61] Haque MA, Kurokawa T, Gong JP. Super tough double network hydrogels and their application as biomaterials. Polymer. 2012;53:1805-1822.

[62] Huang X, Li J, Luo J, Gao Q, Mao A, Li J. Research progress on double-network hydrogels. Mater Today Commun. 2021;29:102757.

[63] Chen J, Wu T, Zhang L, et al. Flexible ionic-gel strain sensor with double network high conductivity and high frost-resistance using electrohydrodynamic printing method. Addit Manuf. 2022;58:103021.

[64] Yasui T, Kamio E, Matsuyama H. Tough and stretchable inorganic/organic double network ion gel containing gemini-type ionic liquid as a multiple hydrogen bond cross-linker. RSC Adv. 2019;9:11870-11876.

[65] Yasui T, Kamio E, Matsuyama H. Inorganic/organic double-network ion gels with partially developed silica-particle network. Langmuir. 2018;34:10622-10633.

[66] Wang Z, Cui H, Liu M, et al. Tough transparent 3D-printable and self-healing poly(ethylene glycol)-gel (PEGgel). Adv Mater. 2022;34:2107791.

[67] Liu C, Qi J, He B, Zhang H, Ju J, Yao X. Ionic conductive gels based on deep eutectic solvents. Int J Smart Nano Mater. 2021;12:337-350.

[68] Fu Y, Chen L, Xu F, Li X, Li Y, Sun J. Spontaneous self-healing ionogels for efficient and reliable carbon dioxide separation. J Mater Chem A. 2022;10:4695-4702.

[69] Saruwatari A, Tamate R, Kokubo H, Watanabe M. Photohealable ion gels based on the reversible dimerisation of anthracene. Chem Commun. 2018;54:13371-13374.

[70] Zhong Y, Nguyen GTM, Plesse C, Vidal F, Jager EWH. Highly conductive photolithographically patternable ionogels for flexible and stretchable electrochemical devices. ACS Appl Mater Interfaces. 2018;10:21601-21611.

[71] Li T, Wang Y, Li S, Liu X, Sun J. Mechanically robust elastic and healable ionogels for highly sensitive ultra-durable ionic skins. Adv Mater. 2020;32:2002706.

[72] Xiang S, Chen S, Yao M, Zheng F, Lu Q. Strain sensor based on a flexible polyimide ionogel for application in high- and low-temperature environments. J Mater Chem C. 2019;7:9625-9632.

[73] Liu K, Lv J, Fan G, et al. Flexible and robust bacterial cellulose-based ionogels with high thermoelectric properties for low-grade heat harvesting. Adv Funct Mater. 2021;32:2107105.

[74] Lee H, Erwin A, Buxton ML, et al. Shape persistent highly conductive ionogels from ionic liquids reinforced with cellulose nanocrystal network. Adv Funct Mater. 2021;31:2103083.

[75] Sun J, Lu G, Zhou J, Yuan Y, Zhu X, Nie J. Robust physically linked double-network ionogel as a flexible bimodal sensor. ACS Appl Mater Interfaces. 2020;12:14272-14279.

[76] Dinh Xuan H, Timothy B, Park HY, et al. Super stretchable and durable electroluminescent devices based on double-network ionogels. Adv Mater. 2021;33:2008849.

[77] Hopson C, Villar-Chavero MM, Domínguez JC, Alonso MV, Oliet M, Rodriguez F. Cellulose ionogels a perspective of the last decade: a review. Carbohydr Polymers. 2021;274:118663.

[78] Qin H, Owyeung RE, Sonkusale SR, Panzer MJ. Highly stretchable and nonvolatile gelatin-supported deep eutectic solvent gel electrolyte-based ionic skins for strain and pressure sensing. J Mater Chem C. 2019;7:601-608.

[79] Li Z, Wang J, Hu R, Lv C, Zheng J. A highly ionic conductive healable and adhesive polysiloxane-supported ionogel. Macromol Rapid Commun. 2019;40:1800776.

[80] Lee JH, Lee AS, Lee JC, Hong SM, Hwang SS, Koo CM. Multifunctional mesoporous ionic gels and scaffolds derived from polyhedral oligomeric silsesquioxanes. ACS Appl Mater Interfaces. 2017;9:3616-3623.

[81] Ye T, Wang Q, Tian C, et al. Multifunctional electronic skin based on perovskite intermediate gels. Adv Electron Mater. 2020;6:1901291.

[82] Han S, Zhi X, Xia Y, et al. All resistive pressure-temperature bimodal sensing E-skin for object classification. Small. 2023;19:2301593.

[83] Lu D, Zhu M, Li X, et al. Thermosensitive hydrogel-based high performance flexible sensors for multi-functional e-skins. J Mater Chem A. 2023;11:18247-18261.

[84] Shang C, Xu Q, Liang N, Zhang J, Li L, Peng Z. Multi-parameter e-skin based on biomimetic mechanoreceptors and stress field sensing. npj Flexible Electronics. 2023;7:19.

[85] Miao P, Wang J, Zhang C, Sun M, Cheng S, Liu H. Graphene nanostructure-based tactile sensors for electronic skin applications. Nano Micro Lett. 2019;11:71.

[86] Pierre Claver U, Zhao G. Recent progress in flexible pressure sensors based electronic skin. Adv Eng Mater. 2021;23:2001187.

[87] Zhao C, Wang Y, Tang G, et al. Ionic flexible sensors: mechanisms materials structures and applications. Adv Funct Mater. 2022;32:2110417.

[88] Luque GC, Picchio ML, Martins APS, et al. 3D printable and biocompatible iongels for body sensor applications. Adv Electron Mater. 2021;7:2100178.

[89] Aguzin A, Luque GC, Ronco LI, et al. Gelatin and tannic acid based iongels for muscle activity recording and stimulation electrodes. ACS Biomater Sci Eng. 2022;8:2598-2609.

[90] Lai QT, Sun QJ, Tang Z, Tang XG, Zhao XH. Conjugated polymer-based nanocomposites for pressure sensors. Molecules. 2023;28:1627.

[91] Dinh Le TS, An J, Huang Y, et al. Ultrasensitive anti-interference voice recognition by bio-inspired skin-attachable self-cleaning acoustic sensors. ACS Nano. 2019;13:13293-13303.

[92] Huo Z, Peng Y, Zhang Y, et al. Recent advances in large-scale tactile sensor arrays based on a transistor matrix. Adv Mater Interfaces. 2018;5:1801061.

[93] Wu H, Su Z, Shi M, et al. Self-powered noncontact electronic skin for motion sensing. Adv Funct Mater. 2017;28:1704641.

[94] Georgopoulou A, Clemens F. Piezoresistive elastomer-based composite strain sensors and their applications. ACS Appl Electron Mater. 2020;2:1826-1842.

[95] Chen W, Liu LX, Zhang HB, Yu ZZ. Kirigami-inspired highly stretchable conductive and hierarchical Ti₃C₂T_x MXene films for efficient electromagnetic interference shielding and pressure sensing. ACS Nano. 2021;15:7668-7681.

[96] Han C, Zhang H, Chen Q, et al. A directional piezoelectric sensor based on anisotropic PVDF/MXene hybrid foam enabled by unidirectional freezing. Chem Eng J. 2022;450:138280.

[97] Zhang L, Li S, Zhu Z, et al. Recent progress on structure manipulation of poly(vinylidene fluoride)-based ferroelectric polymers for enhanced piezoelectricity and applications. Adv Funct Mater. 2023;33:2301302.

[98] Yang X, Zhang M, Xie M, et al. Highly sensitive piezoelectric e-skin design based on electromechanical coupling concept. Adv Electron Mater. 2023;9:2201339.

[99] Yuan H, Lei T, Qin Y, Yang R. Flexible electronic skins based on piezoelectric nanogenerators and piezotronics. Nano Energy. 2019;59:84-90.

[100] Xu L, Huang Z, Deng Z, et al. A transparent highly stretchable solvent-resistant recyclable multifunctional ionogel with underwater self-healing and adhesion for reliable strain sensors. Adv Mater. 2021;33:2105306.

[101] Yu Z, Wu P. Water-resistant ionogel electrode with tailorable mechanical properties for aquatic ambulatory physiological signal monitoring. Adv Funct Mater. 2021;31:2107226.

[102] Wu Q, McDowell MT, Qi Y. Effect of the electric double layer (EDL) in multicomponent electrolyte reduction and solid electrolyte interphase (SEI) formation in lithium batteries. J Am Chem Soc. 2023;145:2473-2484.

[103] Sharma S, Pradhan GB, Chhetry A, et al. Graphene-polymer nanocomposites electrode with ionic nanofibrous membrane for highly sensitive supercapacitive pressure sensor. Nano Today. 2023;48:101698.

[104] Zou Q, Lei Z, Xue T, Li S, Ma Z, Su Q. Highly sensitive flexible pressure sensor based on ionic dielectric layer with hierarchical ridge microstructure. Sens Actuators, A. 2020;313:112218.

[105] Kwon JH, Kim YM, Moon HC. Porous ion gel: a versatile ionotronic sensory platform for high-performance wearable ionoskins with electrical and optical dual output. ACS Nano. 2021;15:15132-15141.

[106] Chen W, Yan X. Progress in achieving high-performance piezoresistive and capacitive flexible pressure sensors: a review. J Mater Sci Technol. 2020;43:175-188.

[107] He J, Zhang Y, Zhou R, et al. Recent advances of wearable and flexible piezoresistivity pressure sensor devices and its future prospects. J Materiomics. 2020;6:86-101.

[108] Sun Q, Seung W, Kim BJ, Seo S, Kim SW, Cho JH. Active matrix electronic skin strain sensor based on piezopotential-powered graphene transistors. Adv Mater. 2015;27:3411-3417.

[109] Cheng Y, Zhu W, Lu X, Wang C. Mechanically robust stretchable autonomously adhesive and environmentally tolerant triboelectric electronic skin for self-powered healthcare monitoring and tactile sensing. Nano Energy. 2022;102:107636.

[110] Lee JI, Choi H, Kong SH, et al. Visco-poroelastic electrochemiluminescence skin with piezo-ionic effect. Adv Mater. 2021;33:2100321.

[111] Ghosh T, Kandpal S, Rani C, Chaudhary A, Kumar R. Recipe for fabricating optimized solid-state electrochromic devices and its know-how: challenges and future. Adv Opt Mater. 2023;11:2203126.

[112] Alberto ME, De Simone BC, Cospito S, et al. Experimental and theoretical characterization of a new synthesized extended viologen. Chem Phys Lett. 2012;552:141-145.

[113] Shi Y, Liu J, Li M, Zheng J, Xu C. Novel electrochromic-fluorescent bi-functional devices based on aromatic viologen derivates. Electrochim Acta. 2018;285:415-423.

[114] Bechinger C, Ferrere S, Zaban A, Sprague J, Gregg BA. Photoelectrochromic windows and displays. Nature. 1996;383:608-610.

[115] Jensen J, Hösel M, Dyer AL, Krebs FC. Development and manufacture of polymer-based electrochromic devices. Adv Funct Mater. 2015;25:2073-2090.

[116] Palenzuela J, Viñuales A, Odriozola I, Cabañero G, Grande HJ, Ruiz V. Flexible viologen electrochromic devices with low operational voltages using reduced graphene oxide electrodes. ACS Appl Mater Interfaces. 2014;6:14562-14567.

[117] Cai G, Eh ALS, Ji L, Lee PS. Recent advances in electrochromic smart fenestration. Adv Sustain Syst. 2017;1:1700074.

[118] Wen RT, Niklasson GA, Granqvist CG. Strongly improved electrochemical cycling durability by adding iridium to electrochromic nickel oxide films. ACS Appl Mater Interfaces. 2015;7:9319-9322.

[119] Gavim AEX, Santos GH, de Souza EH, et al. Influence of electrolyte distribution in PEDOT:PSS based flexible electrochromic devices. Chem Phys Lett. 2017;689:212-218.

[120] Bousalem S, Zeggai FZ, Baltach H, Benyoucef A. Physical and electrochemical investigations on hybrid materials synthesized by polyaniline with various amounts of ZnO nanoparticle. Chem Phys Lett. 2020;741:137095.

[121] Hoshino K, Nakajima R, Okuma M. Improved electrochromic performance of viologen at an ITO-nanoparticle film electrode. Appl Surf Sci. 2014;313:569-576.

[122] Kim K-W, Oh H, Bae JH, Kim H, Moon HC, Kim SH. Electrostatic-force-assisted dispensing printing of electrochromic gels for low-voltage displays. ACS Appl Mater Interfaces. 2017;9:18994-19000.

[123] Kao SY, Lu HC, Kung CW, Chen HW, Chang TH, Ho KC. Thermally cured dual functional viologen-based all-in-one electrochromic devices with panchromatic modulation. ACS Appl Mater Interfaces. 2016;8:4175-4184.

[124] Gadgil B, Damlin P, Ääritalo T, Kvarnström C. Electrosynthesis of viologen cross-linked polythiophene in ionic liquid and its electrochromic properties. Electrochim Acta. 2014;133:268-274.

[125] Sydam R, Ghosh A, Deepa M. Enhanced electrochromic write–erase efficiency of a device with a novel viologen: 11′-bis(2-(1H-indol-3-yl)ethyl)-44′-bipyridinium diperchlorate. Org Electron. 2015;17:33-43.

[126] DeLongchamp DM, Hammond PT. High-contrast electrochromism and controllable dissolution of assembled Prussian blue/polymer nanocomposites. Adv Funct Mater. 2004;14:224-232.

[127] Wang X, Guo L, Cao S, Zhao W. Highly stable viologens-based electrochromic devices with low operational voltages utilizing polymeric ionic liquids. Chem Phys Lett. 2020;749:137434.

[128] Oh H, Seo DG, Yun TY, Lee SB, Moon HC. Novel viologen derivatives for electrochromic ion gels showing a green-colored state with improved stability. Org Electron. 2017;51:490-495.

[129] Moon HC, Kim CH, Lodge TP, Frisbie CD. Multicolored low-power flexible electrochromic devices based on ion gels. ACS Appl Mater Interfaces. 2016;8:6252-6260.

[130] Zhang Y, Guo M, Li G, et al. Ultrastable viologen ionic liquids-based ionogels for visible strain sensor integrated with electrochromism electrofluorochromism and strain sensing. CCS Chemistry. 2023;5:1917-1930.

[131] Poh WC, Eh ALS, Wu W, Guo X, Lee PS. Rapidly photocurable solid-state poly(ionic liquid) ionogels for thermally robust and flexible electrochromic devices. Adv Mater. 2022;34:2206952.

[132] Sun P, Chen J, Li Y, et al. Deep eutectic solvent-based gel electrolytes for flexible electrochromic devices with excellent high/low temperature durability. InfoMat. 2023;5:12363.

[133] Chen L, Weng M, Zhou Z, et al. Large-deformation curling actuators based on carbon nanotube composite: advanced-structure design and biomimetic application. ACS Nano. 2015;9:12189-12196.

[134] Yu Y, Maeda T, Mamiya J, Ikeda T. Photomechanical effects of ferroelectric liquid-crystalline elastomers containing azobenzene chromophores. Angew Chem Int Ed. 2007;46:881-883.

[135] Harmon ME, Tang M, Frank CW. A microfluidic actuator based on thermoresponsive hydrogels. Polymer. 2003;44:4547-4556.

[136] Kim B, Lee MG, Lee YP, Kim Y, Lee G. An earthworm-like micro robot using shape memory alloy actuator. Sens Actuators, A. 2006;125:429-437.

[137] Hegde C, Su J, Tan JMR, He K, Chen X, Magdassi S. Sensing in soft robotics. ACS Nano. 2023;17:15277-15307.

[138] Choe JK, Kim J, Song H, Bae J, Kim J. A soft self-sensing tensile valve for perceptive soft robots. Nat Commun. 2023;14:3942.

[139] Pelrine R, Kornbluh R, Pei Q, Joseph J. High-speed electrically actuated elastomers with strain greater than 100%. Science. 2000;287:836-839.

[140] Hines L, Petersen K, Lum GZ, Sitti M. Soft actuators for small-scale robotics. Adv Mater. 2017;29:1603483.

[141] Liu C, Busfield JJC, Zhang K. An electric self-sensing and variable-stiffness artificial muscle. Adv Intell Syst. 2023;5:2300131.

[142] Khan AQ, Shafiq M, Li J, et al. Recent developments in artificial spider silk and functional gel fibers. SmartMat. 2024;4:e1189.

[143] Kitazawa Y, Ueno K, Watanabe M. Advanced materials based on polymers and ionic liquids. Chem Rec. 2018;18:391-409.

[144] Watanabe M, Imaizumi S, Yasuda T, Kokubo H. Ion gels for ionic polymer actuators. In: Soft Actuators. 2014:141-156.

[145] Kokubo H, Sano R, Murai K, Ishii S, Watanabe M. Ionic polymer actuators using poly(ionic liquid) electrolytes European. Polym J. 2018;106:266-272.

[146] Imaizumi S, Kokubo H, Watanabe M. Polymer actuators using ion-gel electrolytes prepared by self-assembly of ABA-triblock copolymers. Macromolecules. 2011;45:401-409.

[147] Kotal M, Kim J, Kim KJ, Oh IK. Sulfur and nitrogen co-doped graphene electrodes for high-performance ionic artificial muscles. Adv Mater. 2016;28:1610-1615.

[148] Yan Y, Santaniello T, Bettini LG, et al. Electroactive ionic soft actuators with monolithically integrated gold nanocomposite electrodes. Adv Mater. 2017;29:1606109.

[149] Shioiri R, Kokubo H, Horii T, et al. Polymer electrolytes based on a homogeneous poly(ethylene glycol) network and their application to polymer actuators. Electrochim Acta. 2019;298:866-873.

[150] Tamate R, Ueki T. Adaptive ion-gel: stimuli-responsive and self-healing ion gels. Chem Rec. 2023;23:202300043.

[151] Ikeda T, Mamiya J, Yu Y. Photomechanics of liquid-crystalline elastomers and other polymers. Angew Chem Int Ed. 2007;46:506-528.

[152] Liu YY, Liu ZQ, Wang YQ, et al. Light-driven domain switching on a photochromic. Ferroelectric Cryst Growth Des. 2023;23:2602-2608.

[153] Ikeda T, Nakano M, Yu Y, Tsutsumi O, Kanazawa A. Anisotropic bending and unbending behavior of azobenzene liquid-crystalline gels by light exposure. Adv Mater. 2003;15:201-205.

[154] Athanassiou A, Kalyva M, Lakiotaki K, Georgiou S, Fotakis C. All-optical reversible actuation of photochromic-polymer microsystems. Adv Mater. 2005;17:988-992.

[155] Kobatake S, Takami S, Muto H, Ishikawa T, Irie M. Rapid and reversible shape changes of molecular crystals on photoirradiation. Nature. 2007;446:778-781.

[156] Lu W, Wang R, Si M, et al. Synergistic fluorescent hydrogel actuators with selective spatial shape/color-changing behaviors via interfacial supramolecular assembly. SmartMat. 2024;5:e1190.

[157] Ma X, Lan X, Wu L, et al. Photo-induced actuator using temperature and light dual responsive azobenzene containing ion gel in ionic liquid. Eur Polym J. 2020;123:109446.

[158] Saez J, Glennon T, Czugala M, et al. Reusable ionogel-based photo-actuators in a lab-on-a-disc. Sens Actuators, B. 2018;257:963-970.

[159] Guo Y, Yin F, Li Y, Shen G, Lee JC. Incorporating wireless strategies to wearable devices enabled by a photocurable hydrogel for monitoring pressure information. Adv Mater. 2023;35:2300855.

[160] Yadav P, Sahay K, Verma A, Maurya DK, Yadav BC. Applications of multifunctional triboelectric nanogenerator (TENG) devices: materials and prospects. Sustain Energy Fuels. 2023;7:3796-3831.

[161] Wang C, Guo H, Wang P, Li J, Sun Y, Zhang D. An advanced strategy to enhance TENG output: reducing triboelectric charge decay. Adv Mater. 2023;35:2209895.

[162] Wang Y, Yang Y, Wang ZL. Triboelectric nanogenerators as flexible power sources. npj Flex Electron. 2017;1:10.

[163] Li C, Guo H, Wu Z, Wang P, Zhang D, Sun Y. Self-healable triboelectric nanogenerators: marriage between self-healing polymer chemistry and triboelectric devices. Adv Funct Mater. 2023;33:2208372.

[164] Sun L, Chen S, Guo Y, et al. Ionogel-based highly stretchable transparent durable triboelectric nanogenerators for energy harvesting and motion sensing over a wide temperature range. Nano Energy. 2019;63:103847.

[165] Zhao G, Zhang Y, Shi N, et al. Transparent and stretchable triboelectric nanogenerator for self-powered tactile sensing. Nano Energy. 2019;59:302-310.

[166] Fan FR, Tian ZQ, Wang ZL. Flexible triboelectric generator. Nano Energy. 2012;1:328-334.

[167] Wang ZL. Triboelectric nanogenerators as new energy technology for self-powered systems and as active mechanical and chemical sensors. ACS Nano. 2013;7:9533-9557.

[168] Pace G, del Rio Castillo AE, Lamperti A, Lauciello S, Bonaccorso F. 2D materials-based electrochemical triboelectric nanogenerators. Adv Mater. 2023;35:2211037.

[169] Ye BU, Kim BJ, Ryu J, Lee JY, Baik JM, Hong K. Electrospun ion gel nanofibers for flexible triboelectric nanogenerator: electrochemical effect on output power. Nanoscale. 2015;7:16189-16194.

[170] Liao H, Zhong W, Li T, et al. A review of self-healing electrolyte and their applications in flexible/stretchable energy storage devices. Electrochim Acta. 2022;404:139730.

[171] Chen X, Liang L, Hu W, Liao H, Zhang Y. POSS hybrid poly(ionic liquid) ionogel solid electrolyte for flexible lithium batteries. J Power Sources. 2022;542:231766.

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