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Reviews

Liquid crystal elastomers: an introduction and review of emerging technologies

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Pages 78-107 | Received 14 May 2018, Accepted 26 Sep 2018, Published online: 10 Oct 2018

References

  • Oxtoby DW. Liquid crystals: the fourth state of matter (Saeva, Franklin D.). New York (NY): ACS Publications; 1981.
  • Warner M, Terentjev EM. Nematic elastomers—A new state of matter? Prog Polym Sci. 1996;21(5):853–891. PubMed PMID: WOS:A1996VZ27100003; English. doi:10.1016/S0079-6700(96)00013-5.
  • Wermter H, Finkelmann H. Liquid crystalline elastomers as artificial muscles. e-Polymers. 2001;1(1):111–123.
  • Thomsen DL, Keller P, Naciri J, et al. Liquid crystal elastomers with mechanical properties of a muscle. Macromolecules. 2001;34(17):5868–5875.
  • De Gennes PG, Hébert M, Kant R. Artificial muscles based on nematic gels. Macromol Symp. 1997;113(1):39–49. doi:10.1002/masy.19971130107.
  • Buguin A, Li M-H, Silberzan P, et al. Micro-actuators: when artificial muscles made of nematic liquid crystal elastomers meet soft lithography. J Am Chem Soc. 2006;128(4):1088–1089.
  • Li MH, Keller P. Artificial muscles based on liquid crystal elastomers. Philos Trans A Math Phys Eng Sci. 2006 Oct 15;364(1847):2763–2777. PubMed PMID: 16973488. doi:10.1098/rsta.2006.1853.
  • Shenoy DK, Thomsen DL III, Srinivasan A, et al. Carbon coated liquid crystal elastomer film for artificial muscle applications. Sens Actuators A. 2002;96(2):184–188.
  • Yamada M, Kondo M, Ji M, et al. Photomobile polymer materials: towards light-driven plastic motors. Angew Chem Int Ed. 2008;47(27):4986–4988. doi:10.1002/anie.200800760.
  • Behl M, Lendlein A. Actively moving polymers. Soft Matter. 2007;3(1):58–67. PubMed PMID: ISI:000246006400006.
  • Brommel F, Kramer D, Finkelmann H. Preparation of liquid crystalline elastomers. Adv Polym Sci. 2012;250:1–48. doi:10.1007/12_2012_168.
  • Ohm C, Brehmer M, Zentel R. Liquid crystalline elastomers as actuators and sensors. Adv Mater. 2010;22(31):3366–3387.
  • Kularatne RS, Kim H, Boothby JM, et al. Liquid crystal elastomer actuators: synthesis, alignment, and applications. J Polym Sci, Part B: Polym Phys. 2017;55(5):395–411.
  • Lagerwall JPF. An introduction to the physics of liquid crystals. In: Fernandez-Nieves A, Puertas AM, editors. Fluids, colloids and soft materials: An introduction to soft matter physics. Hoboken (NJ): John Wiley & Sons, Inc; 2016. p. 307–340.
  • Lagerwall JPF, Scalia G. A new era for liquid crystal research: applications of liquid crystals in soft matter nano-, bio- and microtechnology. Curr Appl Phys. 2012 2012/11/01/;12(6):1387–1412. https://doi.org/10.1016/j.cap.2012.03.019.
  • Liu D, Broer DJ. Liquid crystal polymer networks: preparation, properties, and applications of films with patterned molecular alignment. Langmuir. 2014;30(45):13499–13509.
  • White TJ, Broer DJ. Programmable and adaptive mechanics with liquid crystal polymer networks and elastomers. Nat Mater. 2015 Nov;14(11):1087–1098. PubMed PMID: 26490216. doi:10.1038/nmat4433.
  • White TJ. Photomechanical effects in liquid crystalline polymer networks and elastomers. J Polym Sci Part B: Polym Phys. 2018;56(9):695–705. doi:10.1002/polb.24576.
  • White TJ. Light to work transduction and shape memory in glassy, photoresponsive macromolecular systems: trends and opportunities. J Polym. Sci Part B: Polym Phys. 2012 Jul 1;50(13):877–880. PubMed PMID: ISI:000304347500001; English. doi:10.1002/Polb.23079.
  • Lee KM, Koerner H, Vaia RA, et al. Light-activated shape memory of glassy, azobenzene liquid crystalline polymer networks. Soft Matter. 2011;7(9):4318–4324. PubMed PMID: ISI:000289634000032; English.
  • Visschers F, Hendrikx M, Zhan Y, et al. Liquid crystal polymers with motile surfaces. Soft Matter. 2018;14:4898–4912.
  • de Gennes P-G, Prost J. The physics of liquid crystals. Vol. 83. Oxford: Oxford university press; 1995.
  • Collings PJ. Liquid crystals: nature’s delicate phase of matter. Princeton (NJ): Princeton University Press; 2002.
  • Yu H. Dancing with light: advances in photofunctional liquid-crystalline materials. Boca Raton (FL): CRC Press; 2015.
  • Menzel AM. Tuned, driven, and active soft matter. Phys Rep. 2015;554:1–45.
  • Wolf JR. Review: main chain hydrogen-bonded liquid crystalline polymers. Liq Cryst Rev. 2014;2(1):28–46. doi:10.1080/21680396.2014.929984.
  • Martin JD, Keary CL, Thornton TA, et al. Metallotropic liquid crystals formed by surfactant templating of molten metal halides. Nat Mater. 2006;5(4):271–275.
  • Bengs H, Finkelmann H, Küpfer J, et al. Highly oriented discotic elastomers. Macromol Rapid Commun. 1993;14(7):445–450.
  • Disch S, Finkelmann H, Ringsdorf H, et al. Macroscopically ordered discotic columnar networks. Macromolecules. 1995;28(7):2424–2428.
  • Xie P, Zhang R. Liquid crystal elastomers, networks and gels: advanced smart materials. J Mater Chem. 2005;15(26):2529–2550.
  • Brömmel F, Kramer D, Finkelmann H. Preparation of liquid crystalline elastomers. liquid crystal elastomers: materials and applications. New York (NY): Springer; 2012. p. 1–48.
  • de Haan LT, Schenning AP, Broer DJ. Programmed morphing of liquid crystal networks. Polymer (Guildf). 2014;55(23):5885–5896.
  • Bisoyi HK, Kumar S. Discotic nematic liquid crystals: science and technology. Chem Soc Rev.. 2010;39(1):264–285.
  • Andrienko D. Introduction to liquid crystals. Bad Marienberg: IMPRS school; 2006.
  • Cotton J, Hardouin F. Chain conformation of liquid-crystalline polymers studied by small-angle neutron scattering. Prog Polym Sci. 1997;22(4):795–828.
  • Brömmel F, Stille W, Finkelmann H, et al. Molecular dynamics and biaxiality of nematic polymers and elastomers. Soft Matter. 2011;7(6):2387–2401.
  • Leube HF, Finkelmann H. New liquid-crystalline side-chain polymers with large transversal polarizability. Macromol Chem Phys. 1990;191(11):2707–2715.
  • Leube HF, Finkelmann H. Optical investigations on a liquid-crystalline side-chain polymer with biaxial nematic and biaxial smectic A phase. Macromol Chem Phys. 1991;192(6):1317–1328.
  • Severing K, Saalwächter K. Biaxial nematic phase in a thermotropic liquid-crystalline side-chain polymer. Phys Rev Lett.. 2004;92(12):125501.
  • Severing K, Stibal-Fischer E, Hasenhindl A, et al. Phase biaxiality in nematic liquid crystalline side-chain polymers of various chemical constitutions. J Phys Chem B. 2006;110(32):15680–15688.
  • Warner M, Terentjev EM. Liquid crystal elastomers. Vol. 120. Oxford: OUP Oxford; 2003.
  • Flory PJ. Principles of polymer chemistry. Ithaca (NY): Cornell University Press; 1953.
  • Hardouin F, Lecommandoux S, editors. Relationship between structure and conformation in liquid crystalline polymers. Zug: Macromolecular Symposia: Wiley Online Library; 1997.
  • Ohm C, Brehmer M, Zentel R. Applications of liquid crystalline elastomers. liquid crystal elastomers: materials and applications. New York (NY): Springer; 2012. p. 49–93.
  • Schuhladen S, Preller F, Rix R, et al. Iris-like tunable aperture employing liquid-crystal elastomers. Adv Mater. 2014;26(42):7247–7251.
  • Terentjev EM. Liquid-crystalline elastomers. J Phys: Condens Matter. 1999;11(24):R239–R257.
  • Boisse P. Advances in composites manufacturing and process design. Cambridge: Woodhead Publishing; 2015.
  • Aguilera C, Bartulin J, Hisgen B, et al. Liquid crystalline main chain polymers with highly flexible siloxane spacers. Macromol Chem Phys. 1983;184(2):253–262.
  • Courty S, Mine J, Tajbakhsh A, et al. Nematic elastomers with aligned carbon nanotubes: New electromechanical actuators. Europhysics Lett (EPL). 2003;64(5):654–660.
  • Gebhard E, Zentel R. Ferroelectric liquid crystalline elastomers, 2. variation of mesogens and network density. Macromol Chem Phys. 2000;201(8):911–922.
  • Hu J-s, Zhang B-y, Sun K, et al. Side chain cholesteric liquid crystalline elastomers: synthesis and phase behaviour. Liq Cryst. 2003;30(11):1267–1275.
  • Keller P. Photo-crosslinkable liquid-crystalline side-chain polysiloxanes. Chem Mater. 1990;2(1):3–4.
  • Küpfer J, Finkelmann H. Nematic liquid single crystal elastomers. Macromol Rapid Commun. 1991;12(12):717–726.
  • Schüring H, Stannarius R, Tolksdorf C, et al. Liquid crystal elastomer balloons. Macromolecules. 2001;34(12):3962–3972.
  • Stannarius R, Köhler R, Rössle M, et al. Study of smectic elastomer films under uniaxial stress. Liq Cryst. 2004;31(7):895–906.
  • Tajbakhsh A, Terentjev E. Spontaneous thermal expansion of nematic elastomers. Eur Phys J E: Soft Matter Biol Phys. 2001;6(2):181–188.
  • Jia Y, Zhang B, Zhou E, et al. Synthesis and characterization of network liquid crystal elastomers and thermosets. J Appl Polym Sci. 2002;85(5):1104–1109.
  • Lewis FD, Salvi GD. Platinum (II) Bis (.beta.-diketonates) as photoactivated hydrosilation catalysts. Inorg Chem. 1995;34(12):3182–3189.
  • Bohnert R, Finkelmann H. Liquid-crystalline side-chain AB block copolymers by direct anionic polymerization of a mesogenic methacrylate. Macromol Chem Phys. 1994;195(2):689–700.
  • Vasilets VN, Kovalchuk AV, Yuranova T, et al. Orientational order of a nematic polymer grafted on polytetrafluoroethylene. Polym Adv Technol. 2000;11(7):330–333.
  • Vasilets VN, Kovalchuk AV, Yuranova T, et al. Sandwich structure containing liquid crystal polymer grafted on polymer support. Polym Adv Technol. 1996;7(3):173–176.
  • Mouquinho A, Saavedra M, Maiau A, et al. Films based on New methacrylate monomers: synthesis, characterisation and electro-optical properties. Mol Cryst Liq Cryst. 2011;542(1):132/[654]–140/[662].
  • Ahn S-k, Deshmukh P, Kasi RM. Shape memory behavior of side-chain liquid crystalline polymer networks triggered by dual transition temperatures. Macromolecules. 2010;43(17):7330–7340.
  • Xia Y, Verduzco R, Grubbs RH, et al. Well-defined liquid crystal gels from telechelic polymers. J Am Chem Soc. 2008;130(5):1735–1740.
  • Yang H, Liu M-X, Yao Y-W, et al. Polysiloxane-based liquid crystalline polymers and elastomers prepared by thiol–ene chemistry. Macromolecules. 2013;46(9):3406–3416.
  • Bergmann GH, Finkelmann H, Percec V, et al. Liquid-crystalline main-chain elastomers. Macromol Rapid Commun. 1997;18(5):353–360.
  • Rousseau IA, Mather PT. Shape memory effect exhibited by smectic-C liquid crystalline elastomers. J Am Chem Soc. 2003;125(50):15300–15301.
  • Urayama K. Selected issues in liquid crystal elastomers and gels. Macromolecules. 2007;40(7):2277–2288.
  • Donnio B, Wermter H, Finkelmann H. A simple and versatile synthetic route for the preparation of main-chain, liquid-crystalline elastomers. Macromolecules. 2000;33(21):7724–7729.
  • Bispo M, Guillon D, Donnio B, et al. Main-chain liquid crystalline elastomers: monomer and cross-linker molecular control of the thermotropic and elastic properties. Macromolecules. 2008;41(9):3098–3108.
  • Burke KA, Mather PT. Soft shape memory in main-chain liquid crystalline elastomers. J Mater Chem. 2010;20(17):3449–3457.
  • Burke KA, Mather PT. Evolution of microstructure during shape memory cycling of a main-chain liquid crystalline elastomer. Polymer (Guildf). 2013;54(11):2808–2820.
  • Burke KA, Rousseau IA, Mather PT. Reversible actuation in main-chain liquid crystalline elastomers with varying crosslink densities. Polymer (Guildf). 2014;55(23):5897–5907.
  • Krause S, Dersch R, Wendorff JH, et al. Photocrosslinkable liquid crystal main-chain polymers: thin films and electrospinning. Macromol Rapid Commun. 2007;28(21):2062–2068.
  • Krause S, Zander F, Bergmann G, et al. Nematic main-chain elastomers: coupling and orientational behavior. C R Chim. 2009;12(1-2):85–104.
  • Ortiz C, Wagner M, Bhargava N, et al. Deformation of a polydomain, smectic liquid crystalline elastomer. Macromolecules. 1998;31(24):8531–8539.
  • Rousseau IA, Qin H, Mather PT. Tailored phase transitions via mixed-mesogen liquid crystalline polymers with silicon-based spacers. Macromolecules. 2005;38(10):4103–4113.
  • Agrawal A, Luchette P, Palffy-Muhoray P, et al. Surface wrinkling in liquid crystal elastomers. Soft Matter. 2012;8(27):7138–7142.
  • Beyer P, Braun L, Zentel R. (Photo) crosslinkable smectic LC main-chain polymers. Macromol Chem Phys. 2007;208(22):2439–2448.
  • Beyer P, Terentjev EM, Zentel R. Monodomain liquid crystal main chain elastomers by photocrosslinking. Macromol Rapid Commun. 2007;28(14):1485–1490. doi:10.1002/marc.200700210.
  • Zentel R, Reckert G. Liquid crystalline elastomers based on liquid crystalline side group, main chain and combined polymers. Macromol Chem Phys. 1986;187(8):1915–1926.
  • Ware T, White T. Programmed liquid crystal elastomers with tunable actuation strain. Polym Chem. 2015;6(26):4835–4844.
  • Ware TH, McConney ME, Wie JJ, et al. Voxelated liquid crystal elastomers. Science. 2015;347(6225):982–984.
  • Wie JJ, Lee KM, Ware TH, et al. Twists and turns in glassy, liquid crystalline polymer networks. Macromolecules. 2015;48(4):1087–1092.
  • Xia Y, Cedillo-Servin G, Kamien RD, et al. Guided folding of nematic liquid crystal elastomer sheets into 3D via patterned 1D microchannels. Adv Mater. 2016;28(43):9637–9643.
  • Komp A, Rühe J, Finkelmann H. A versatile preparation route for thin free-standing liquid single crystal elastomers. Macromol Rapid Commun. 2005;26(10):813–818.
  • Sánchez-Ferrer A, Fischl T, Stubenrauch M, et al. Photo-crosslinked side-chain liquid-crystalline elastomers for microsystems. Macromol Chem Phys. 2009;210(20):1671–1677.
  • de Haan LT, Gimenez-Pinto V, Konya A, et al. Accordion-like actuators of multiple 3D patterned liquid crystal polymer films. Adv Funct Mater. 2014;24(9):1251–1258.
  • de Haan LT, Sánchez-Somolinos C, Bastiaansen CM, et al. Engineering of complex order and the macroscopic deformation of liquid crystal polymer networks. Angew Chem Int Ed. 2012;51(50):12469–12472.
  • Babakhanova G, Turiv T, Guo Y, et al. Liquid crystal elastomer coatings with programmed response of surface profile. arXiv preprint arXiv:180101076. 2018.
  • Guo Y, Jiang M, Peng C, et al. High-Resolution and high-throughput plasmonic photopatterning of complex molecular orientations in liquid crystals. Adv Mater. 2016;28(12):2353–2358.
  • Hotta A, Terentjev E. Dynamic soft elasticity in monodomain nematic elastomers. Eur Phys J E: Soft Matter Biol Phy. 2003;10(4):291–301.
  • Komp A, Finkelmann H. A New type of macroscopically oriented smectic-A liquid crystal elastomer. Macromol Rapid Commun. 2007;28(1):55–62.
  • Yakacki C, Saed M, Nair D, et al. Tailorable and programmable liquid-crystalline elastomers using a two-stage thiol–acrylate reaction. RSC Adv. 2015;5(25):18997–19001.
  • Nishikawa E, Yamamoto J, Yokoyama H, et al. Smectic a elastomers with uniform homeotropic orientation obtained by applying a biaxial mechanical field. Macromol Rapid Commun. 2004;25(5):611–617.
  • Nishikawa E, Finkelmann H. Orientation behavior of smectic polymer networks by uniaxial mechanical fields. Macromol Chem Phys. 1997;198(8):2531–2549.
  • Davis F, Mitchell G. Liquid crystal elastomers: controlled crosslinking in the liquid crystal phase. Polymer (Guildf). 1996;37(8):1345–1351.
  • Biggins J, Warner M, Bhattacharya K. Elasticity of polydomain liquid crystal elastomers. J Mech Phys Solids. 2012;60(4):573–590.
  • Urayama K, Kohmon E, Kojima M, et al. Polydomain−monodomain transition of randomly disordered nematic elastomers with different cross-linking histories. Macromolecules. 2009;42(12):4084–4089.
  • Traugutt N, Volpe R, Bollinger M, et al. Liquid-crystal order during synthesis affects main-chain liquid-crystal elastomer behavior. Soft Matter. 2017;13(39):7013–7025.
  • Kim H, Boothby JM, Ramachandran S, et al. Tough, shape-changing materials: crystallized liquid crystal elastomers. Macromolecules. 2017;50(11):4267–4275.
  • Biggins J, Warner M, Bhattacharya K. Supersoft elasticity in polydomain nematic elastomers. Phys Rev Lett.. 2009;103(3):037802.
  • Tsuchitani A, Ashida H, Urayama K. Pronounced effects of cross-linker geometries on the orientation coupling between dangling mesogens and network backbones in side-chain type liquid crystal elastomers. Polymer (Guildf). 2015;61:29–35.
  • Clarke S, Hotta A, Tajbakhsh A, et al. Effect of crosslinker geometry on equilibrium thermal and mechanical properties of nematic elastomers. Phys Rev E. 2001;64(6):061702.
  • Clarke S, Hotta A, Tajbakhsh A, et al. Effect of cross-linker geometry on dynamic mechanical properties of nematic elastomers. Phys Rev E. 2002;65(2):021804.
  • Selinger JV, Jeon HG, Ratna B. Isotropic-nematic transition in liquid-crystalline elastomers. Phys Rev Lett.. 2002;89(22):225701.
  • Kolb HC, Finn M, Sharpless KB. Click chemistry: diverse chemical function from a few good reactions. Angew Chem, Int Ed. 2001;40(11):2004–2021.
  • Johnson JA, Finn M, Koberstein JT, et al. Construction of linear polymers, dendrimers, networks, and other polymeric architectures by copper-catalyzed azide-alkyne cycloaddition “click” chemistry. Macromol Rapid Commun. 2008:29(12–13):1052–1072.
  • Lub J, Broer DJ, van den Broek N. Synthesis and polymerization of liquid crystals containing vinyl and mercapto groups. European J Org Chem. 1997;1997(11):2281–2288.
  • Yang H, Buguin A, Taulemesse J-M, et al. Micron-sized main-chain liquid crystalline elastomer actuators with ultralarge amplitude contractions. J. Am. Chem. Soc.. 2009;131(41):15000–15004.
  • Nair DP, Podgórski M, Chatani S, et al. The thiol-michael addition click reaction: a powerful and widely used tool in materials chemistry. Chem Mater. 2014;26(1):724–744.
  • Chan JW, Hoyle CE, Lowe AB, et al. Nucleophile-initiated thiol-michael reactions: effect of organocatalyst, thiol, and ene. Macromolecules. 2010;43(15):6381–6388.
  • Chan JW, Wei H, Zhou H, et al. The effects of primary amine catalyzed thio-acrylate michael reaction on the kinetics, mechanical and physical properties of thio-acrylate networks. Eur Polym J. 2009;45(9):2717–2725.
  • Saed MO, Torbati AH, Starr CA, et al. Thiol-acrylate main-chain liquid-crystalline elastomers with tunable thermomechanical properties and actuation strain. J Polym Sci, Part B: Polym Phys. 2017;55(2):157–168.
  • Saed MO, Volpe RH, Traugutt NA, et al. High strain actuation liquid crystal elastomers via modulation of mesophase structure. Soft Matter. 2017;13(41):7537–7547.
  • Xia Y, Zhang X, Yang S. Instant locking of molecular ordering in liquid crystal elastomers by oxygen-mediated thiol-acrylate click reactions. Angew Chem. 2018;130(20):5767–5770.
  • Kloxin CJ, Bowman CN. Covalent adaptable networks: smart, reconfigurable and responsive network systems. Chem Soc Rev.. 2013;42(17):7161–7173.
  • Kloxin CJ, Scott TF, Adzima BJ, et al. Covalent adaptable networks (CANs): a unique paradigm in cross-linked polymers. Macromolecules. 2010;43(6):2643–2653.
  • Ware TH, Perry ZP, Middleton CM, et al. Programmable liquid crystal elastomers prepared by thiol–ene photopolymerization. ACS Macro Lett. 2015;4(9):942–946.
  • Engle L, Wagener K. A review of thermally controlled covalent bond formation in polymer chemistry. journal of macromolecular science. Part C: Polymer Reviews. 1993;33(3):239–257.
  • Yang H, Yu K, Mu X, et al. A molecular dynamics study of bond exchange reactions in covalent adaptable networks. Soft Matter. 2015;11(31):6305–6317.
  • Wang Z, Tian H, He Q, et al. Reprogrammable, reprocessible, and self-healable liquid crystal elastomer with exchangeable disulfide bonds. ACS Appl Mater Interfaces. 2017;9(38):33119–33128.
  • Ube T, Kawasaki K, Ikeda T. Photomobile liquid-crystalline elastomers with rearrangeable networks. Adv Mater. 2016;28(37):8212–8217.
  • Pei Z, Yang Y, Chen Q, et al. Mouldable liquid-crystalline elastomer actuators with exchangeable covalent bonds. Nat Mater. 2014;13(1):36–41.
  • McBride MK, Hendrikx M, Liu D, et al. Photoinduced plasticity in cross-linked liquid crystalline networks. Adv Mater. 2017;29(17):1606509.
  • Li Y, Zhang Y, Rios O, et al. Photo-responsive liquid crystalline epoxy networks with exchangeable disulfide bonds. RSC Adv. 2017;7(59):37248–37254.
  • Li Y, Zhang Y, Rios O, et al. Liquid crystalline epoxy networks with exchangeable disulfide bonds. Soft Matter. 2017;13(29):5021–5027.
  • Hanzon DW, Traugutt NA, McBride MK, et al. Adaptable liquid crystal elastomers with transesterification-based bond exchange reactions. Soft Matter. 2018;14:951–960.
  • Kawasaki K, Ube T, Ikeda T. Remoldable crosslinked liquid-crystalline polysiloxane with side chain mesogens based on exchangeable crosslinks. Mol Cryst Liq Cryst. 2015;614(1):62–66.
  • Yang Y, Pei Z, Li Z, et al. Making and remaking dynamic 3D structures by shining light on flat liquid crystalline vitrimer films without a mold. J Am Chem Soc.. 2016;138(7):2118–2121.
  • Pei Z, Yang Y, Chen Q, et al. Regional shape control of strategically assembled multishape memory vitrimers. Adv Mater. 2016;28(1):156–160.
  • Kotikian A, Truby RL, Boley JW, et al. 3D printing of liquid crystal elastomeric actuators with spatially programed nematic order. Adv Mater. 2018;30:1706164.
  • Yuan C, Roach DJ, Dunn CK, et al. 3D printed reversible shape changing soft actuators assisted by liquid crystal elastomers. Soft Matter. 2017;13(33):5558–5568.
  • Zeng H, Wani OM, Wasylczyk P, et al. Self-regulating iris based on light-actuated liquid crystal elastomer. Adv Mater. 2017;29(30):1701814.
  • Tibbits S, editor. The emergence of “4D printing”. TED conference; 2013.
  • Ge Q, Qi HJ, Dunn ML. Active materials by four-dimension printing. Appl Phys Lett. 2013;103(13):131901.
  • Yu K, Dunn ML, Qi HJ. Digital manufacture of shape changing components. Extreme Mech Lett. 2015;4:9–17.
  • Mao Y, Yu K, Isakov MS, et al. Sequential self-folding structures by 3D printed digital shape memory polymers. Sci Rep. 2015;5:13616.
  • Ding Z, Weeger O, Qi HJ, et al. 4D rods: 3D structures via programmable 1D composite rods. Mater Des. 2018;137:256–265.
  • Ding Z, Yuan C, Peng X, et al. Direct 4D printing via active composite materials. Sci Adv. 2017;3(4):e1602890.
  • Tibbits S. 4D printing: multi-material shape change. Archit Des. 2014;84(1):116–121.
  • Lewis JA. Direct ink writing of 3D functional materials. Adv Funct Mater. 2006;16(17):2193–2204.
  • Gladman AS, Matsumoto EA, Nuzzo RG, et al. Biomimetic 4D printing. Nat Mater. 2016;15(4):413–418.
  • Wu J, Yuan C, Ding Z, et al. Multi-shape active composites by 3D printing of digital shape memory polymers. Sci Rep. 2016;6:24224.
  • Choong YYC, Maleksaeedi S, Eng H, et al. 4D printing of high performance shape memory polymer using stereolithography. Mater Des. 2017;126:219–225.
  • Miao S, Zhu W, Castro NJ, et al. 4D printing smart biomedical scaffolds with novel soybean oil epoxidized acrylate. Sci Rep. 2016;6:27226.
  • Melchels FP, Feijen J, Grijpma DW. A review on stereolithography and its applications in biomedical engineering. Biomaterials. 2010;31(24):6121–6130.
  • Ambulo C, Burroughs JJ, Boothby JM, et al. 4D printing of liquid crystal elastomers. ACS Appl Mater Interfaces. 2017;9:37332–37339.
  • Ahn BY, Duoss EB, Motala MJ, et al. Omnidirectional printing of flexible, stretchable, and spanning silver microelectrodes. Science. 2009;323(5921):1590–1593.
  • Rus D, Tolley MT. Design, fabrication and control of soft robots. Nature. 2015;521(7553):467–475.
  • Kim S, Laschi C, Trimmer B. Soft robotics: a bioinspired evolution in robotics. Trends Biotechnol. 2013;31(5):287–294.
  • Shepherd RF, Ilievski F, Choi W, et al. Multigait soft robot. Proc Natl Acad Sci U S A. 2011;108(51):20400–20403.
  • Trivedi D, Rahn CD, Kier WM, et al. Soft robotics: biological inspiration, state of the art, and future research. Appl Bionics Biomech. 2008;5(3):99–117.
  • Mazzolai B, Margheri L, Cianchetti M, et al. Soft-robotic arm inspired by the octopus: II. from artificial requirements to innovative technological solutions. Bioinspir Biomim. 2012;7(2):025005.
  • Lin H-T, Leisk GG, Trimmer B. GoQBot: a caterpillar-inspired soft-bodied rolling robot. Bioinspir Biomim. 2011;6(2):026007.
  • Brown E, Rodenberg N, Amend J, et al. Universal robotic gripper based on the jamming of granular material. Proc Natl Acad Sci U S A. 2010;107(44):18809–18814.
  • Pfeifer R, Lungarella M, Iida F. The challenges ahead for bio-inspired ‘soft’ robotics. Commun ACM. 2012;55(11):76–87.
  • Lendlein A, Kelch S. Shape-memory polymers. Angew Chem, Int Ed. 2002;41(12):2034–2057.
  • Lendlein A, Jiang H, Jünger O, et al. Light-induced shape-memory polymers. Nature. 2005;434(7035):879–882.
  • Yu K, Ge Q, Qi HJ. Reduced time as a unified parameter determining fixity and free recovery of shape memory polymers. Nat Commun. 2014;5:3066.
  • Lee MJ, Jung SH, Kim GS, et al. Actuation of the artificial muscle based on ionic polymer metal composite by electromyography (EMG) signals. J Intell Mater Syst Struct. 2007;18(2):165–170.
  • Bar-Cohen Y. Artificial muscles based on electroactive polymers as an enabling tool in biomimetics. P I Mech Eng Part C: J Mech Eng Sci. 2007;221(10):1149–1156.
  • Laschi C, Cianchetti M. Soft robotics: new perspectives for robot bodyware and control. Front Bioeng Biotechnol. 2014;2:3.
  • Mao Y, Ding Z, Yuan C, et al. 3D printed reversible shape changing components with stimuli responsive materials. Sci Rep. 2016;6:24761.
  • Raviv D, Zhao W, McKnelly C, et al. Active printed materials for complex self-evolving deformations. Sci Rep. 2015;4:7422.
  • Suzumori K, Endo S, Kanda T, et al., editors. A bending pneumatic rubber actuator realizing soft-bodied manta swimming robot. Robotics and Automation, 2007 IEEE International Conference on; IEEE; 2007.
  • Wehner M, Truby RL, Fitzgerald DJ, et al. An integrated design and fabrication strategy for entirely soft, autonomous robots. Nature. 2016;536(7617):451–455.
  • Yamada M, Kondo M, Miyasato R, et al. Photomobile polymer materials—Various three-dimensional movements. J Mater Chem.. 2009;19(1):60–62.
  • Kohlmeyer RR, Chen J. Wavelength-Selective, IR light-driven hinges based on liquid crystalline elastomer composites. Angew Chem Int Ed. 2013;52(35):9234–9237.
  • Rogóż M, Zeng H, Xuan C, et al. Light-Driven soft robot mimics caterpillar locomotion in natural scale. Adv Opt Mater. 2016;4(11):1689–1694.
  • Camacho-Lopez M, Finkelmann H, Palffy-Muhoray P, et al. Fast liquid-crystal elastomer swims into the dark. Nat Mater. 2004;3(5):307–310.
  • Zeng H, Wasylczyk P, Parmeggiani C, et al. Light-Fueled microscopic walkers. Adv Mater. 2015;27(26):3883–3887.
  • Palagi S, Mark AG, Reigh SY, et al. Structured light enables biomimetic swimming and versatile locomotion of photoresponsive soft microrobots. Nat Mater. 2016;15(6):647–653.
  • Qian X, Chen Q, Yang Y, et al. Untethered recyclable tubular actuators with versatile locomotion for soft continuum robots. Adv Mater. 2018:30:1801103.
  • Petsch S, Rix R, Khatri B, et al. Smart artificial muscle actuators: liquid crystal elastomers with integrated temperature feedback. Sens Actuators, A. 2015;231:44–51.
  • Robinson G, Davies JBC, editors. Continuum robots-a state of the art. Robotics and automation, 1999. Proceedings 1999 IEEE International Conference on; IEEE; 1999.
  • Jones BA, Gray RL, Turlapati K, editors. Three dimensional statics for continuum robotics. Intelligent robots and systems, 2009. IROS 2009. IEEE/RSJ International Conference on; IEEE; 2009.
  • Boyer F, Porez M, Khalil W. Macro-continuous computed torque algorithm for a three-dimensional eel-like robot. IEEE Trans Robot. 2006;22(4):763–775.
  • Petsch S, Rix R, Reith P, et al., editors. A thermotropic liquid crystal elastomer micro-actuator with integrated deformable micro-heater. Micro Electro Mechanical Systems (MEMS), 2014 IEEE 27th International Conference on; IEEE; 2014.
  • Prévôt M, Hegmann E. From biomaterial, biomimetic, and polymer to biodegradable and biocompatible liquid crystal elastomer cell scaffolds. Advances in bioinspired and biomedical materials volume 2. New York (NY): ACS Publications; 2017. p. 3–45.
  • Gao Y, Mori T, Manning S, et al. Biocompatible 3D liquid crystal elastomer cell scaffolds and foams with primary and secondary porous architecture. ACS Macro Lett. 2016;5(1):4–9.
  • Prévôt M, Andro H, Alexander S, et al. Liquid crystal elastomer foams with elastic properties specifically engineered as biodegradable brain tissue scaffolds. Soft Matter. 2018;14(3):354–360.
  • Agrawal A, Adetiba O, Kim H, et al. Stimuli-responsive liquid crystal elastomers for dynamic cell culture. J Mater Res. 2015;30(4):453–462.
  • Martella D, Paoli P, Pioner JM, et al. Liquid crystalline networks toward regenerative medicine and tissue repair. Small. 2017;13(46):1702677.
  • Koçer G, ter Schiphorst J, Hendrikx M, et al. Light-responsive hierarchically structured liquid crystal polymer networks for harnessing cell adhesion and migration. Adv Mater. 2017;29(27):1606407.
  • Finkelmann H, Kim ST, Munoz A, et al. Tunable mirrorless lasing in cholesteric liquid crystalline elastomers. Adv Mater. 2001;13(14):1069–1072.
  • Van Oosten CL, Bastiaansen CW, Broer DJ. Printed artificial cilia from liquid-crystal network actuators modularly driven by light. Nat Mater. 2009;8(8):677–682.
  • Fleischmann EK, Ohm C, Serra C, et al. Preparation of soft microactuators in a continuous flow synthesis using a liquid-crystalline polymer crosslinker. Macromol Chem Phys. 2012;213(18):1871–1878.
  • Schmidt-Mende L, Fechtenkötter A, Müllen K, et al. Self-organized discotic liquid crystals for high-efficiency organic photovoltaics. Science. 2001;293(5532):1119–1122.
  • Verbunt PP, Tsoi S, Debije MG, et al. Increased efficiency of luminescent solar concentrators after application of organic wavelength selective mirrors. Opt Express. 2012;20(105):A655–A668.
  • Wei D. New liquid crystal molecule advances organic solar cells. Abington-on-Thames: Taylor & Francis; 2015.
  • Gimenez-Pinto V, Ye F, Mbanga B, et al. Modeling out-of-plane actuation in thin-film nematic polymer networks: from chiral ribbons to auto-origami boxes via twist and topology. Sci Rep. 2017;7:45370.
  • Pasini P, Skačej G, Zannoni C. A microscopic lattice model for liquid crystal elastomers. Chem Phys Lett. 2005;413(4–6):463–467.
  • Stannarius R, Köhler R, Dietrich U, et al. Structure and elastic properties of smectic liquid crystalline elastomer films. Phys Rev E. 2002;65(4):041707.
  • Ilnytskyi JM, Saphiannikova M, Neher D, et al. Modelling elasticity and memory effects in liquid crystalline elastomers by molecular dynamics simulations. Soft Matter. 2012;8(43):11123–11134.
  • Konya A, Gimenez-Pinto V, Selinger RL. Modeling defects, shape evolution, and programmed auto-origami in liquid crystal elastomers. Front Mater. 2016;3:24.
  • Zhu W, Shelley M, Palffy-Muhoray P. Modeling and simulation of liquid-crystal elastomers. Phys Rev E. 2011;83(5):051703.
  • Chung H, Choi J, Yun J-H, et al. Light and thermal responses of liquid-crystal-network films: a finite element study. Phys Rev E. 2015;91(4):042503.
  • Mistry D, Morgan PB, Clamp JH, et al. New insights into the nature of semi-soft elasticity and “mechanical-fréedericksz transitions” in liquid crystal elastomers. Soft Matter. 2018;14(8):1301–1310.
  • Hébert M, Kant R, De Gennes P-G. Dynamics and thermodynamics of artificial muscles based on nematic gels. J Phys I. 1997;7(7):909–919.
  • De Gennes PG, Hébert M, Kant R, editors. Artificial muscles based on nematic gels. Zug: Macromolecular Symposia: Wiley Online Library; 1997.

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