title: Abiotic tooth enamel.
abstract: Tooth enamel comprises parallel microscale and nanoscale ceramic columns or prisms interlaced with a soft protein matrix. This structural motif is unusually consistent across all species from all geological eras. Such invariability-especially when juxtaposed with the diversity of other tissues-suggests the existence of a functional basis. Here we performed ex vivo replication of enamel-inspired columnar nanocomposites by sequential growth of zinc oxide nanowire carpets followed by layer-by-layer deposition of a polymeric matrix around these. We show that the mechanical properties of these nanocomposites, including hardness, are comparable to those of enamel despite the nanocomposites having a smaller hard-phase content. Our abiotic enamels have viscoelastic figures of merit (VFOM) and weight-adjusted VFOM that are similar to, or higher than, those of natural tooth enamels-we achieve values that exceed the traditional materials limits of 0.6 and 0.8, respectively. VFOM values describe resistance to vibrational damage, and our columnar composites demonstrate that light-weight materials of unusually high resistance to structural damage from shocks, environmental vibrations and oscillatory stress can be made using biomimetic design. The previously inaccessible combinations of high stiffness, damping and light weight that we achieve in these layer-by-layer composites are attributed to efficient energy dissipation in the interfacial portion of the organic phase. The in vivo contribution of this interfacial portion to macroscale deformations along the tooth's normal is maximized when the architecture is columnar, suggesting an evolutionary advantage of the columnar motif in the enamel of living species. We expect our findings to apply to all columnar composites and to lead to the development of high-performance load-bearing materials.
authors.affiliation: Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.|Department of Chemical Engineering, Myongji University, Yongin 17058, South Korea.
authors.forename: Bongjun
authors.initials: B
authors.lastname: Yeom
authors.affiliation: Mechanical Engineering-Engineering Mechanics, Michigan Technological University, Houghton, Michigan 49931, USA.
authors.forename: Trisha
authors.initials: T
authors.lastname: Sain
authors.affiliation: Illinois Applied Research Institute, University of Illinois at Urbana-Champaign, Illinois 61820, USA.
authors.forename: Naida
authors.initials: N
authors.lastname: Lacevic
authors.affiliation: Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Daria
authors.initials: D
authors.lastname: Bukharina
authors.affiliation: Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.|Department of Chemical Engineering, Kyonggi University, Suwon 443-760, South Korea.
authors.forename: Sang-Ho
authors.initials: SH
authors.lastname: Cha
authors.affiliation: Department of Aerospace Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.|William E. Boeing Department of Aeronautics and Astronautics, University of Washington, Seattle 98195, USA.
authors.forename: Anthony M
authors.initials: AM
authors.lastname: Waas
authors.affiliation: Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.|Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.|Program in Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Ellen M
authors.initials: EM
authors.lastname: Arruda
authors.affiliation: Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.|Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.|Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.|Biointerfaces Institute, University of Michigan, Ann Arbor, Michigan 48109, USA.|Michigan Center for Integrative Research in Critical Care, Ann Arbor, Michigan 48109, USA.
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Kotov
mesh_terms: D000818:Animals; D040761:Biomimetic Materials / Q000737:chemistry*; D032701:Biomimetics; D003743:Dental Enamel / Q000737:chemistry*; D006244:Hardness; D006801:Humans; D053761:Nanocomposites / Q000737:chemistry*; D053770:Nanowires / Q000737:chemistry*; D014070:Tooth / Q000737:chemistry*; D014732:Vibration; D015034:Zinc Oxide / Q000737:chemistry
chemical_list: D015034:Zinc Oxide