Machine technology frequently puts magnetic or electrostatic repulsive forces to practical use, as in maglev trains, vehicle suspensions or non-contact bearings1,2. In contrast, materials design overwhelmingly focuses on attractive interactions, such as in the many advanced polymer-based composites, where inorganic fillers interact with a polymer matrix to improve mechanical properties. However, articular cartilage strikingly illustrates how electrostatic repulsion can be harnessed to achieve unparalleled functional efficiency: it permits virtually frictionless mechanical motion within joints, even under high compression3,4. Here we describe a composite hydrogel with anisotropic mechanical properties dominated by electrostatic repulsion between negatively charged unilamellar titanate nanosheets5 embedded within it. Crucial to the behaviour of this hydrogel is the serendipitous discovery of cofacial nanosheet alignment in aqueous colloidal dispersions subjected to a strong magnetic field, which maximizes electrostatic repulsion6 and thereby induces a quasi-crystalline structural ordering7,8 over macroscopic length scales and with uniformly large face-to-face nanosheet separation. We fix this transiently induced structural order by transforming the dispersion into a hydrogel9,10 using light-triggered in situ vinyl polymerization11. The resultant hydrogel, containing charged inorganic structures that align cofacially in a magnetic flux12,13,14,15,16,17,18,19, deforms easily under shear forces applied parallel to the embedded nanosheets yet resists compressive forces applied orthogonally. We anticipate that the concept of embedding anisotropic repulsive electrostatics within a composite material, inspired by articular cartilage, will open up new possibilities for developing soft materials with unusual functions.
Your institute does not have access to this article
Open Access articles citing this article.
Nature Communications Open Access 11 July 2022
Nanoscale Research Letters Open Access 02 March 2020
Nature Communications Open Access 22 January 2020
Subscribe to Journal
Get full journal access for 1 year
only $3.90 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Get time limited or full article access on ReadCube.
All prices are NET prices.
Hull, J. R. Superconducting bearings. Supercond. Sci. Technol. 13, R1–R15 (2000)
Rhim, W. K. et al. An electrostatic levitator for high-temperature containerless materials processing in 1-G. Rev. Sci. Instrum. 64, 2961–2970 (1993)
Scott, J. E. Elasticity in extracellular matrix ‘shape modules’ of tendon, cartilage, etc. A sliding proteoglycan-filament model. J. Physiol. 553, 335–343 (2003)
Dean, D., Han, L., Grodzinsky, A. J. & Ortiz, C. Compressive nanomechanics of opposing aggrecan macromolecules. J. Biomech. 39, 2555–2565 (2006)
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)
Anandarajah, A. & Ning, L. Numerical study of the electrical double-layer repulsion between nonparallel clay particles of finite length. Int. J. Numer. Analyt. Meth. Geomech. 15, 683–703 (1991)
Cui, H. G. et al. Spontaneous and X-ray-triggered crystallization at long range in self-assembling filament networks. Science 327, 555–559 (2010)
Palmer, L. C. et al. Long-range ordering of highly charged self-assembled nanofilaments. J. Am. Chem. Soc. 136, 14377–14380 (2014)
Wu, Z. L. et al. Anisotropic hydrogel from complexation-driven reorientation of semirigid polyanion at Ca2+ diffusion flux front. Macromolecules 44, 3535–3541 (2011)
Wu, J., Zhao, Q., Sun, J. & Zhou, Q. Preparation of poly(ethylene glycol) aligned porous cryogels using a unidirectional freezing technique. Soft Matter 8, 3620–3626 (2012)
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)
Eguchi, M., Angelone, M. S., Yennawar, H. P. & Mallouk, T. E. Anisotropic alignment of lamellar potassium hexaniobate microcrystals and nanoscrolls in a static magnetic field. J. Phys. Chem. C 112, 11280–11285 (2008)
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)
Osada, M. et al. Ferromagnetism in two-dimensional Ti0. 8Co0. 2O2 nanosheets. Phys. Rev. B 73, 153301 (2006)
Prosser, S., Hunt, S. A., DiNatale, J. A. & Vold, R. R. Magnetically aligned membrane model systems with positive order parameter: switching the sign of S zz with paramagnetic ions. J. Am. Chem. Soc. 118, 269–270 (1996)
Tan, C., Fung, B. M. & Cho, G. Phospholipid bicelles that align with their normals parallel to the magnetic field. J. Am. Chem. Soc. 124, 11827–11832 (2002)
Kleinschmidt, F., Hickl, M., Saalwächter, K., Schmidt, C. & Finkelmann, H. Lamellar liquid single crystal hydrogels: synthesis and investigation of anisotropic water diffusion and swelling. Macromolecules 38, 9772–9782 (2005)
Haque, M. A., Kamita, G., Kurokawa, T., Tsujii, K. & Gong, J. P. Unidirectional alignment of lamellar bilayer in hydrogel: one-dimensional swelling, anisotropic modulus, and stress/strain tunable structural color. Adv. Mater. 22, 5110–5114 (2010)
Erb, R. M., Libanori, R., Rothfuchs, N. & Studart, A. R. Composites reinforced in three dimensions by using low magnetic fields. Science 335, 199–204 (2012)
Wang, Q. et al. High-water-content mouldable hydrogels by mixing clay and a dendritic molecular binder. Nature 463, 339–343 (2010)
Tamesue, S. et al. Linear versus dendritic molecular binders for hydrogel network formation with clay nanosheets: studies with ABA triblock copolyethers carrying guanidinium ion pendants. J. Am. Chem. Soc. 135, 15650–15655 (2013)
Maret, G. & Dransfeld, K. Biomolecules and polymers in high steady magnetic fields. Top. Appl. Phys. 57, 143–204 (1985)
Löwen, H. Colloidal soft matter under external control. J. Phys. Condens. Matter 13, R415–R432 (2001)
Uyeda, C. Diamagnetic anisotropies of oxide minerals. Phys. Chem. Miner. 20, 77–81 (1993)
Torbet, J., Freyssinet, J. M. & Hudry-Clergeon, G. Oriented fibrin gels formed by polymerization in strong magnetic fields. Nature 289, 91–93 (1981)
Feng, S. et al. Hierarchical structure in oriented fibers of a dendronized polymer. Macromolecules 42, 281–287 (2009)
Verwey, E. J. W. & Overbeek, J. Th. G. Theory of the Stability of Lyophobic Colloids (Elsevier, 1948)
Podsiadlo, P. et al. Ultrastrong and stiff layered polymer nanocomposites. Science 318, 80–83 (2007)
Munch, E. et al. Tough, bio-inspired hybrid materials. Science 322, 1516–1520 (2008)
Budtova, T. & Navard, P. Swelling-induced birefringence of a polyelectrolyte gel strongly interacting with metal ions. Macromolecules 30, 6556–6558 (1997)
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 Council for Science, Technology and Innovation (Cabinet Office, Government of Japan). The synchrotron X-ray diffraction experiments were performed at BL45XU in SPring-8 with the approval of the RIKEN SPring-8 Center (proposal 20140073).
The authors declare no competing financial interests.
This file contains Supplementary Text and Data, Supplementary Figures 1–18, Supplementary Tables 1-2 and Supplementary References. (PDF 9710 kb)
This video shows the vibration isolation of hydrogel pillars containing horizontally oriented TiNSs. (MOV 5745 kb)
This video shows the vibration isolation of hydrogel pillars containing vertically oriented TiNSs. (MOV 2480 kb)
This video shows the vibration isolation of hydrogel pillars containing randomly oriented TiNSs. (MOV 4334 kb)
This video shows the oscillation-induced deformations of single hydrogel cylinders without any weight at their free edge. (MOV 31453 kb)
About this article
Cite this article
Liu, M., Ishida, Y., Ebina, Y. et al. An anisotropic hydrogel with electrostatic repulsion between cofacially aligned nanosheets. Nature 517, 68–72 (2015). https://doi.org/10.1038/nature14060
Nature Communications (2022)
Nature Materials (2022)
Hydrogels totally from inorganic nanosheets and water with mechanical robustness, self-healing, controlled lubrication and anti-corrosion
Nano Research (2022)
Journal of Materials Science (2022)
Vertically aligned two-dimensional materials-based thick electrodes for scalable energy storage systems
Nano Research (2021)