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Thermoresponsive actuation enabled by permittivity switching in an electrostatically anisotropic hydrogel


Electrostatic repulsion, long used for attenuating surface friction1,2, is not typically employed for the design of bulk structural materials. We recently developed a hydrogel3 with a layered structure consisting of cofacially oriented electrolyte nanosheets4. Because this unusual geometry imparts a large anisotropic electrostatic repulsion5 to the hydrogel interior, the hydrogel resisted compression orthogonal to the sheets but readily deformed along parallel shear. Building on this concept, here we show a hydrogel actuator6,7,8,9,10,11 that operates by modulating its anisotropic electrostatics12 in response to changes of electrostatic permittivity associated with a lower critical solution temperature transition13,14. In the absence of substantial water uptake and release, the distance between the nanosheets rapidly expands and contracts on heating and cooling, respectively, so that the hydrogel lengthens and shortens significantly, even in air. An L-shaped hydrogel with an oblique nanosheet configuration can thus act as a unidirectionally proceeding actuator that operates without the need for external physical biases15,16,17,18.

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Figure 1: Thermoresponsive deformation of a hydrogel adopting a layered structure with cofacially oriented unilamellar titanate(IV) nanosheets (TiNSs).
Figure 2: Rapid thermoresponsive deformation of a PNIPA/TiNS hydrogel rod in a glass capillary.
Figure 3: Thermoresponsive deformation profiles of hydrogel films in open air.
Figure 4: Synchronous thermoresponsive changes in the macroscopic shape and nanostructure of a PNIPA/TiNS hydrogel rod.
Figure 5: Unidirectional procession of an L-shaped symmetric PNIPA/TiNS hydrogel actuator.


  1. Rhim, W. K. et al. An electrostatic levitator for high-temperature containerless materials processing in 1-G. Rev. Sci. Instrum. 64, 2961–2970 (1993).

    Article  CAS  Google Scholar 

  2. Hull, J. R. Superconducting bearings. Supercond. Sci. Technol. 13, R1–R15 (2000).

    Article  CAS  Google Scholar 

  3. Liu, M. et al. An anisotropic hydrogel with electrostatic repulsion between cofacially aligned nanosheets. Nature 517, 68–72 (2015).

    Article  CAS  Google Scholar 

  4. Sasaki, T., Watanabe, M., Hashizume, H., Yamada, H. & Nakazawa, H. Macromolecule-like aspects for a colloidal suspension of an exfoliated titanate. Pairwise association of nanosheets and dynamic reassembling process initiated from it. J. Am. Chem. Soc. 118, 8329–8335 (1996).

    Article  CAS  Google Scholar 

  5. Anandarajah, A. & Ning, L. Numerical study of the electrical double-layer repulsion between nonparallel clay particles of finite length. Int. J. Numer. Anal. Methods Geomech. 15, 683–703 (1991).

    Article  Google Scholar 

  6. Schild, H. G. Poly(N-isopropylacrylamide): Experiment, theory and application. Prog. Polym. Sci. 17, 163–249 (1992).

    Article  CAS  Google Scholar 

  7. Maeda, Y., Higuchi, T. & Ikeda, I. Change in hydration state during the coil-globule transition of aqueous solutions of poly(N-isopropylacrylamide) as evidenced by FTIR spectroscopy. Langmuir 16, 7503–7509 (2000).

    Article  CAS  Google Scholar 

  8. Shibayama, M. & Tanaka, T. Volume phase transition and related phenomena of polymer gels. Adv. Polym. Sci. 109, 1993 (2005).

    Google Scholar 

  9. Pelton, R. Temperature-sensitive aqueous microgels. Adv. Colloid Interface Sci. 85, 1–33 (2000).

    Article  CAS  Google Scholar 

  10. Yoshida, R. et al. Comb-type grafted hydrogels with rapid de-swelling response to temperature changes. Nature 374, 240–242 (1995).

    Article  CAS  Google Scholar 

  11. Xia, L.-W., Ju, X.-J., Liu, J.-J., Xie, R. & Chu, L.-Y. Responsive hydrogels with poly(N-isopropylacrylamide-co-acrylic acid) colloidal spheres as building blocks. J. Colloid Interface Sci. 349, 106–113 (2010).

    Article  CAS  Google Scholar 

  12. Verwey, E. J. W. & Overbeek, J. Th. G. Theory of the Stability of Lyophobic Colloids (Elsevier, 1948).

    Google Scholar 

  13. Füllbrandt, M. et al. Dynamics of linear poly(N-isopropylacrylamide) in water around the phase transition investigated by dielectric relaxation spectroscopy. J. Phys. Chem. B 118, 3750–3759 (2014).

    Article  Google Scholar 

  14. Gómez-Galván, F., Lara-Ceniceros, T. & Mercado-Uribe, H. Device for simultaneous measurements of the optical and dielectric properties of hydrogels. Meas. Sci. Technol. 23, 025602 (2012).

    Article  Google Scholar 

  15. Osada, Y., Okuzaki, H. & Hori, H. A polymer gel with electrically driven motility. Nature 355, 242–244 (1992).

    Article  CAS  Google Scholar 

  16. Kohlmeyer, R. R. & Chen, J. Wavelength-selective, IR light-driven hinges based on liquid crystalline elastomer composite. Angew. Chem. Int. Ed. 52, 9234–9237 (2013).

    Article  CAS  Google Scholar 

  17. Morales, D., Palleau, E., Dickey, M. D. & Velev, O. D. Electro-actuated hydrogel walkers with dual responsive legs. Soft Matter 10, 1337–1348 (2014).

    Article  CAS  Google Scholar 

  18. Kim, J. et al. Programming magnetic anisotropy in polymeric microactuators. Nature Mater. 10, 747–752 (2011).

    Article  CAS  Google Scholar 

  19. Ida, S. et al. Photoluminescence of perovskite nanosheets prepared by exfoliation of layered oxides, K2Ln2Ti3O10, KLnNb2O7, and RbLnTa2O7 (Ln: lanthanide ion). J. Am. Chem. Soc. 130, 7052–7059 (2008).

    Article  CAS  Google Scholar 

  20. Osada, M. et al. Ferromagnetism in two-dimensional Ti0.8Co0.2O2 nanosheets. Phys. Rev. B 73, 153301–153301 (2006).

    Article  Google Scholar 

  21. Cui, H. G. et al. Spontaneous and X-ray-triggered crystallization at long range in self-assembling filament networks. Science 327, 555–559 (2010).

    Article  CAS  Google Scholar 

  22. Yao, Z. & de la Cruz, M. O. Electrostatic repulsion-driven crystallization model arising from filament networks. Phys. Rev. E 87, 042605 (2013).

    Article  Google Scholar 

  23. Palmer, L. C. et al. Long-range ordering of highly charged self-assembled nanofilaments. J. Am. Chem. Soc. 136, 14377–14380 (2014).

    Article  CAS  Google Scholar 

  24. Torbet, J., Freyssinet, J. M. & Hudry-Clergeon, G. Oriented fibrin gels formed by polymerization in strong magnetic fields. Nature 289, 91–93 (1981).

    Article  CAS  Google Scholar 

  25. Pagonis, K. & Bokias, G. Upper critical solution temperature-type cononsolvency of poly(N, N-dimethylacrylamide) in water–organic solvent mixtures. Polymer 45, 2149–2153 (2004).

    Article  CAS  Google Scholar 

  26. Fujisawa, T. et al. Small-angle X-ray scattering station at the SPring-8 RIKEN beamline. J. Appl. Crystallogr. 33, 797–800 (2000).

    Article  CAS  Google Scholar 

  27. Smalley, M. Clay Swelling and Colloid Stability (CRC Press, 2006).

    Book  Google Scholar 

  28. Liu, M., Ishida, Y., Ebina, Y., Sasaki, T. & Aida, T. Photolatently modulable hydrogels using unilamellar titania nanosheets as photocatalytic crosslinker. Nature Commun. 4, 2029 (2013).

    Article  Google Scholar 

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This work was financially supported by a Grant-in-Aid for Specially Promoted Research (25000005) on ‘Physically Perturbed Assembly for Tailoring High-Performance Soft Materials with Controlled Macroscopic Structural Anisotropy’. We also acknowledge the ImPACT Program of the Council for Science, Technology and Innovation (Cabinet Office, Government of Japan). Y.S.K. thanks JSPS for a Young Scientist Fellowship. The small-angle X-ray scattering measurements were performed at BL45XU in SPring-8 with the approval of the RIKEN SPring-8 Center (proposal 20140073).

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Authors and Affiliations



Y.S.K. designed and performed all experiments. M.L., Y.I. and T.A. co-designed the experiments. Y.E. and T.S. prepared colloidally dispersed TiNSs. M.O. conducted the permittivity measurements. Y.S.K., Y.I. and T.A. analysed the data and wrote the manuscript. T.H. and M.T. supported the small-angle X-ray scattering measurements at SPring-8.

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Correspondence to Yasuhiro Ishida or Takuzo Aida.

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The authors declare no competing financial interests.

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Kim, Y., Liu, M., Ishida, Y. et al. Thermoresponsive actuation enabled by permittivity switching in an electrostatically anisotropic hydrogel. Nature Mater 14, 1002–1007 (2015).

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