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Preparation of biomimetic photoresponsive polymer springs


Polymer springs that twist under irradiation with light, in a manner that mimics how plant tendrils twist and turn under the effect of differential expansion in different sections of the plant, show potential for soft robotics and the development of artificial muscles. The soft springs prepared using this protocol are typically 1 mm wide, 50 μm thick and up to 10 cm long. They are made from liquid crystal polymer networks in which an azobenzene derivative is introduced covalently as a molecular photo-switch. The polymer network is prepared by irradiation of a twist cell filled with a mixture of shape-persistent liquid crystals, liquid crystals having reactive end groups, molecular photo-switches, some chiral dopant and a small amount of photoinitiator. After postcuring, the soft polymer film is removed and cut into springs, the geometry of which is determined by the angle of cut. The material composing the springs is characterized by optical microscopy, scanning electron microscopy and tensile strength measurements. The springs operate at ambient temperature, by mimicking the orthogonal contraction mechanism that is at the origin of plant coiling. They shape-shift under irradiation with UV light and can be pre-programmed to either wind or unwind, as encoded in their geometry. Once illumination is stopped, the springs return to their initial shape. Irradiation with visible light accelerates the shape reversion.

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Figure 1: Helix-based motion and mirror-image helices in biological systems.
Figure 2
Figure 3: A variety of springs can be prepared by cutting thin stripes in a homogeneous thin film of liquid crystal polymer network (top panel).
Figure 4: A specific liquid crystal cell is required to prepare liquid crystal polymer springs.
Figure 5: Photo-actuated twisting and/or untwisting motion is encoded via orthogonal deformation modes: in all cases, the outside of the ribbon deforms perpendicularly to the inside of the ribbon.
Figure 6: Nonlinear mechanical character of a biomimetic photoresponsive polymer spring (φ = 45°).
Figure 7: Filling of the cell with the liquid crystal pre-polymer mixture.
Figure 8: Photopolymerization.
Figure 9: Opening of the cell.
Figure 10: The procedure allows production of a variety of photoresponsive polymer springs.


  1. Finkelmann, H., Nishikawa, E., Pereira, G.G. & Warner, M.A. New opto-mechanical effect in solids. Phys. Rev. Lett. 87, 015501 (2001).

    Article  CAS  Google Scholar 

  2. Yu, Y., Nakano, M. & Ikeda, T. Directed bending of a polymer film by light. Nature 425, 145 (2003).

    Article  CAS  Google Scholar 

  3. White, T. & Broer, D.J. Programmable and adaptive mechanics with liquid crystal polymer networks and elastomers. Nature Mater. 14, 1087–1098 (2015).

    Article  CAS  Google Scholar 

  4. Wang, J.-S. et al. Hierarchical chirality transfer in the growth of the Towel Gourd tendrils. Sci. Rep. 3, 3102 (2013).

    Article  Google Scholar 

  5. Forterre, Y. & Dumais, J. Generating helices in nature. Science 333, 1715–1716 (2011).

    Article  CAS  Google Scholar 

  6. Isnard, S. & Silk, W.K. Moving with climbing plants from Charles Darwin's time into the 21st century. Am. J. Bot. 96, 1205–1221 (2009).

    Article  Google Scholar 

  7. Evangelista, D., Hotton, S. & Dumais, J. The mechanics of explosive dispersal and self-burial in the seeds of filaree erodium cicutarium. J. Exp. Biol. 214, 521–529 (2011).

    Article  Google Scholar 

  8. Erb, R.M., Sander, J.S., Grisch, R. & Studart, A.R. Self-shaping composites with programmable bioinspired microstructures. Nat. Commun. 4, 1712 (2013).

    Article  Google Scholar 

  9. Zhang, L. & Naumov, P. Light- and humidity-induced motion of an acidochromic film. Angew. Chem. Int. Ed. 54, 8642–8647 (2015).

    Article  CAS  Google Scholar 

  10. Zhang, L., Chizhik, S., Wen, Y. & Naumov, P. Directed motility of hygroresponsive biomimetic actuators. Adv. Funct. Mater. 26, 1040–1053 (2016).

    Article  CAS  Google Scholar 

  11. Wu, Z.L. et al. Three-dimensional shape transformations of hydrogel sheets induced by small-scale modulation of internal stresses. Nat. Commun. 4, 1586 (2013).

    Article  Google Scholar 

  12. de Haan, L.T et al. Humidity-responsive liquid crystalline polymer actuators with an asymmetry in the molecular trigger that bend, fold, and curl. J. Am. Chem. Soc. 136, 10585–10588 (2014).

    Article  CAS  Google Scholar 

  13. Iamsaard, S. et al. Conversion of light into macroscopic helical motion. Nature Chem. 6, 229–235 (2014).

    Article  CAS  Google Scholar 

  14. Harris, K.D. et al. Large amplitude light-induced motion in high elastic modulus polymer actuators. J. Mater. Chem. 15, 5043–5048 (2005).

    Article  CAS  Google Scholar 

  15. Yu, Y., Nakano, M., Shishido, A., Shiono, T. & Ikeda, T. Effect of cross-linking density on photoinduced bending behavior of oriented liquid-crystalline network films containing azobenzene. Chem. Mater. 16, 1637–1643 (2004).

    Article  CAS  Google Scholar 

  16. Dumais, J. & Forterre, Y. Vegetable dynamicks: the role of water in plant movements. Annu. Rev. Fluid Mech. 44, 453–478 (2012).

    Article  Google Scholar 

  17. Witztum, A. & Schulgasser, K. The mechanics of seed expulsion in Acanthaceae. J. Theor. Biol. 176, 531–542 (1995).

    Article  Google Scholar 

  18. Dawson, C., Vincent, J.F.V. & Roca, A.M. How pine cones open. Nature 390, 668 (1997).

    Article  CAS  Google Scholar 

  19. Elbaum, R., Zaltzman, L., Burgert, I. & Fratzl, P. The role of wheat awns in the seed dispersal unit. Science 316, 884–886 (2007).

    Article  CAS  Google Scholar 

  20. Studart, A.R. & Erb, R.M. Bioinspired materials that self-shape through programmed microstructures. Soft Matter 10, 1284–1294 (2014).

    Article  CAS  Google Scholar 

  21. Sawa, Y. et al. Shape selection of twist-nematic-elastomer ribbons. Proc. Natl. Acad. Sci. USA 108, 6364–6368 (2011).

    Article  CAS  Google Scholar 

  22. Sawa, Y. et al. Shape and chirality transitions in off-axis twist nematic elastomer ribbons. Phys. Rev. E 88, 022502 (2013).

    Article  Google Scholar 

  23. Teresi, L. & Varano, V. Modeling helicoid to spiral-ribbon transitions of twist-nematic elastomers. Soft Matter 9, 3081–3088 (2013).

    Article  CAS  Google Scholar 

  24. Wie, J.J. et al. Torsional mechanical responses in azobenzene functionalized liquid crystalline polymer networks. Soft Matter 9, 9303–9310 (2013).

    Article  CAS  Google Scholar 

  25. van Oosten, C.L. et al. Bending dynamics and directionality reversal in liquid crystal network photoactuators. Macromolecules 41, 8592–8596 (2008).

    Article  CAS  Google Scholar 

  26. Liu, D. & Broer, D. J. Liquid crystal polymer networks: preparation, properties, and applications of films with patterned molecular alignment. Langmuir 30, 13499–13509 (2014).

    Article  CAS  Google Scholar 

  27. Liu, D. & Broer, D.J. New insights into photoactivated volume generation boost surface morphing in liquid crystal coatings. Nat. Commun. 6, 8334 (2015).

    Article  CAS  Google Scholar 

  28. Sanchez-Ferrer, A., Merekalov, A. & Finkelmann, H. Opto-mechanical effect in photoactive nematic side-chain liquid-crystalline elastomers. Macromol. Rapid Commun. 32, 671–678 (2011).

    Article  CAS  Google Scholar 

  29. Zeng, H. et al. High-resolution 3D direct laser writing for liquid-crystalline elastomer microstructures. Adv. Mater. 26, 2319–2322 (2014).

    Article  CAS  Google Scholar 

  30. Min Lee, K., Lynch, B.M., Luchette, P. & White, T.J. Photomechanical effects in liquid crystal polymer networks prepared with m-fluoroazobenzene. J. Polym. Sci. A 52, 876–882 (2014).

    Article  CAS  Google Scholar 

  31. Shadmehr, R. & Arbib, A.M. A mathematical analysis of the force-stiffness characteristics of muscles in control of a single joint system. Biol. Cybern. 66, 463–477 (1992).

    Article  CAS  Google Scholar 

  32. Mossety-Leszczak, B., Wlodarska, M., Galina, H. & Bak, G.W. Comparing liquid crystalline properties of two epoxy compounds based on the same azoxy group. Mol. Cryst. Liq. Cryst. 490, 52–66 (2008).

    Article  CAS  Google Scholar 

  33. Li, C. et al. Synthesis of a photoresponsive liquid-crystalline polymer containing azobenzene. Macromol. Rapid Commun. 30, 1928–1935 (2009).

    Article  Google Scholar 

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This work was supported financially by the European Research Council (Starting Grant 307784 to N.K.), the Netherlands Organization for Scientific Research (Vidi Grant to N.K.), the EPSRC (Standard Grant EP/M002144/1 to S.P.F.) and the Royal Society through an International Exchange Grant to S.P.F. and N.K. The authors gratefully acknowledge R. Carloni, A. Cremonese (Robotics and Mechatronics, University of Twente), T. Kudernac and A. Leoncini (Molecular Nanofabrication, University of Twente) for discussions on the mechanical properties of the springs.

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Authors and Affiliations



N.K. and S.P.F. initiated the project and designed the research. S.I., E.V., F.L. and S.-J.A. conducted the experiments and analyzed the data. F.L. conducted the tensile strength measurements. N.K., S.P.F., E.V. and F.L. wrote the manuscript and all authors contributed to discussing the results and the manuscript at all stages.

Corresponding authors

Correspondence to Stephen P Fletcher or Nathalie Katsonis.

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The authors declare no competing financial interests.

Integrated supplementary information

Supplementary Figure 1 Evaluating the thickness of the polymer springs

Cross-section of a liquid crystal polymer film prepared in a commercially available twist cell of nominal thickness 50 μm, observed by scanning electron microscopy. The measured thickness of the film is 43 μm. Scale bar 10 μm.

Supplementary Figure 2 Characterization of the liquid crystal mixture used for the preparation of the biomimetic polymer springs

Differential scanning calorimetry of the liquid crystal mixture without photoinitiator (Irgacure 819). The isotropic to nematic and nematic to crystalline transition are visible respectively at 64.8oC and 12.8 °C.

Supplementary Figure 3 Evaluating the mechanical properties of the springs

Photography of the set-up dedicated to stiffness measurements

Supplementary information

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Iamsaard, S., Villemin, E., Lancia, F. et al. Preparation of biomimetic photoresponsive polymer springs. Nat Protoc 11, 1788–1797 (2016).

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