Erika Griesshaber

Publications (8)7.87 Total impact

• Source

  Available from: Dierk Raabe

  Article: Interdigitating biocalcite dendrites form a 3-D jigsaw structure in brachiopod shells.

  Andreas J Goetz, David R Steinmetz, Erika Griesshaber, Stefan Zaefferer, Dierk Raabe, Klemens Kelm, Stephan Irsen, Angelika Sehrbrock, Wolfgang W Schmahl
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  ABSTRACT: We report a newly discovered dense microstructure of dendrite-like biocalcite that is formed by marine organisms. High spatial resolution electron backscatter diffraction (EBSD) was carried out under specific analytical conditions (15 and 10 kV) on the primary layer of the modern brachiopod Gryphus vitreus. The primary layer of modern brachiopods, previously termed nanocrystalline, is formed by an array of concave/convex calcite grains with interdigitated recesses and protrusions of abutting crystals without any cavities in or between the dendrites. The interface topology of this structure ranges from a few tens of nanometres to tens of micrometres, giving a nanoscale structure to the material fabric. The dendritic grains show a spread of crystallographic orientation of several degrees and can thus be referred to as mesocrystals. Individual dendritic mesocrystals reach sizes in one dimension larger than 20 μm. The preferred crystallographic orientation is similar in the primary and adjacent fibrous shell layers, even though these two layers show completely different crystal morphologies and grain boundary topologies. This observation indicates that two separate control mechanisms are active when the primary and the fibrous shell layers are formed. We propose a growth model for the interdigitated dendritic calcite grain structure based on a precursor of vesicles filled with amorphous calcium carbonate (ACC).
  Acta biomaterialia 02/2011; 7(5):2237-43. · 3.98 Impact Factor
• Article: Mechanical properties of modern calcite- (Mergerlia truncata) and phosphate-shelled brachiopods (Discradisca stella and Lingula anatina) determined by nanoindentation.

  Casjen Merkel, Julia Deuschle, Erika Griesshaber, Susan Enders, Erwin Steinhauser, Rupert Hochleitner, Uwe Brand, Wolfgang W Schmahl
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  ABSTRACT: We measured distribution patterns of hardness and elastic modulus by nanoindentation on shells of the rhynchonelliform brachiopod Mergerlia truncata and the linguliform brachiopods Discradisca stella and Lingula anatina. The rhynchonelliformea produce calcitic shells while the linguliformea produce chitinophosphatic shells. Dorsal and ventral valves, commissure and hinge of the calcitic shell of M. truncata show different nanohardness values (from 2.3 to 4.6 GPa) and E-modulus (from 52 to 76 GPa). The hardness of the biocalcite is always increased compared to inorganic calcite. We attribute the effects to different amounts of inter- and intracrystalline organic matrix. Profiles parallel to the radius of curvature of the valves cutting through the different layers of shell material surprisingly show quite uniform values of nanohardness and modulus of elasticity. Nanoindentation tests on the chitinophosphatic brachiopods D. stella and L. anatina reflect the hierarchical structure composed of laminae with varying degree of mineralization. As a result of the two-phase composite of biopolymer nanofibrils reinforced with Ca-phosphate nanoparticles, nanohardness, and E-modulus correlate almost linearly from (H=0.25 GPa, E=2.5 GPa) to (H=2.5 GPa, E=50 GPa). The mineral provides stiffness and hardness, the biopolymer provides flexibility; and the composite provides fracture toughness. Gradients in the degree of mineralization reduce potential stress concentrations at the interface between stiff mineralized and soft non-mineralized laminae. For the epibenthic chitinophosphatic D. stella the lamination is also present but less pronounced than for the infaunal L. anatina, and the overall distribution of material strength in the cross-sectional profile shows a maximum in the center and a decrease towards the inner and outer shell margins (modulus of elasticity from 30 to 12 GPa, hardness from 1.7 to 0.5 GPa). Accordingly, the two epibenthic forms, calcitic M. truncata and chitinophosphatic D. stella display fairly bulky (homogeneous) nanomechanical properties of their shell materials, while the burrowing infaunal L. anatina is distinctively laminated. The strongly mineralized laminae, which provide the strength to the shell, are also brittle, but keeping them as thin as possible, allows some bending flexibility. This flexibility is not required for the epibenthic life style.
  Journal of Structural Biology 09/2009; 168(3):396-408. · 3.41 Impact Factor
• Article: Electron Backscatter Diffraction Study of Brachiopod Shell Calcite – Microscale Phase and Texture Analysis of a Polycrystalline Biomaterial

  Wolfgang W. Schmahl, Erika Griesshaber, Rolf D. Neuser, Andreas Goetz, Carsten Lüter
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  ABSTRACT: Electron backscatter diffraction (EBSD) is an easy to use and highly automated microdiffraction method suitable for the determination of crystallographic phase and crystallite orientation. The high level of hierarchical structural organization in the shells of marine organisms was studied. Calcite brachiopod shell materials were found to belong to three types of microstructure: nano- to microcrystalline layers of acicular crystals, fiber composites with calcite single crystal fibers with [uv0] morphological axes, and material formed by columnar crystals with [001] morphological axes selected by competitive growth.
  Particle and Particle Systems Characterization 03/2009; 25(5‐6):474 - 478. · 0.49 Impact Factor
• Article: The Ultrastructure of Brachiopod Shells - A Mechanically Optimized Material with Hierarchical Architecture

  Erika Griesshaber, Klemens Kelm, Angelika Sehrbrock, Reinhart Job, Wolfgang W. Schmahl, Werner Mader
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  ABSTRACT: Brachiopod shells consist of low-magnesium calcite and belong to one of the most intriguing species for studies of marine paleoenvironments, variations in oceanographic conditions and ocean chemistry [6, 7, 11 – 13]. We have investigated the ultrastructure together with nano- and microhardness properties of modern brachiopod shells with transmission electron microscopy (TEM), scanning electron microscopy (SEM), nanoindentation and Vickers microhardness analyses. Brachiopod shells are structured into several layers, a thin, outer, hard, protective primary layer composed of randomly oriented nanocrystalline calcite, which is followed inward towards the soft tissue of the animal by a much softer shell segment (secondary layer) built of long calcite fibres, stacked parallely into blocks. The hardness distribution pattern within the shells is non-uniform and varies on scales as small as a few tens of microns. Our results show that the hardness of this biomaterial is controlled by two predominant features: (1.) The morphological orientation of the calcite fibres (not by the crystallographic orientation of the fibres), and (2.) the amount and distribution pattern of organic material between and within the calcite crystals.
  MRS Proceedings. 12/2004; 898.
• Conference Proceeding: The mesocrystalline assembly of the aragonitic material in the bone of Sepia officinalis

  Klemens Kelm, Andreas Ziegler, Erika Griesshaber, Angelika Sehrbrock, Wolfgang W. Schmahl
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  ABSTRACT: Cuttlefish (Sepiidae, Nautilidae, Spirulidae) are the only cephalopods that incorporate a chambered endo-skeleton into their body tissue. The skeleton has a dual function: it is used for skeletal support and as a buoyancy regulation device. Thus cuttlefish bone needs to have extraordinary material properties, that is, in this case again, accomplished by an interplay of architectural design, an elaborate microstructure and the composite (organic-inorganic) nature of the material. We demonstrate the material architecture by means of SEM and TEM investigations.
  MC2011;
• Conference Proceeding: How perfect are sea urchin spine single crystals? Examples from the spine of the sea urchin Holopneustes porosissimus

  Klemens Kelm, Erika Griesshaber, Andreas Götz, Wolfgang W. Schmahl
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  ABSTRACT: Sea urchins are marine animals that crystallize calcite as the major skeleton building material. Regular sea urchins consist of a spherically shaped, calcitc exoskeleton onto that the spines are attached in a radial arrangement. We investigated the Ultrastructure of teh eSpines by means of EBSD and TEM.
  MC2011;
• Conference Proceeding: Biogenic and biomimetic carbonate formation from ACC and PILP precursors

  Erika Griesshaber, H. Gong, Klemens Kelm, D. Volkmer, Wolfgang W. Schmahl
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  ABSTRACT: Biologically formed hard tissues are highly valued prototypes for the synthesis of new materials because of their remarkable structures and evolved mechanical properties. Hierarchical architectures, a composite material design and a strong crystallographic control exerted during the precipitation of bioinorganic crystals characterize these materials. We discuss results about carbonate crystal nucleation and growth from both, the PILP and the biologic ACC precursor phases. Crystal nucleation and growth has been observed in-situ (with light-microscopy and TEM imaging), crystal orientation patterns were recorded by using diffraction methods in SEM (EBSD) and TEM.
  Microscopy Conference MC2011;
• Source

  Available from: Klemens Kelm

  Article: The hierarchical organization in biomaterials: from nanoparticles via mesocrystals to functionality

  Wolfgang W. Schmahl, Klemens Kelm, Erika Griesshaber, Andreas Goetz, Guntram Jordan, Dayin Xu, Casjen Merkel, Uwe Brand, Alan Logan
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  ABSTRACT: As opposed to most human made materials, biologic structural materials employed for skeletons or teeth show a hierarchical architecture, where the components of organic macromolecules and mineral substance are inter-weaved on many length scales in order to form a composite material. In the overall skeleton the organic biopolymer fibres provide flexibility and tensile strength while the mineral provides a high elastic modulus, compressive strength, hardness and resistance to abrasion. The hierarchical composite architecture provides fracture toughness. The morphogenesis of the biomaterial as a whole and of the mineral particles is guided by the organic matrix. In this paper we use the example of rhynchonelliform brachiopods to discuss the nano- to macroscale assemblage.
  Seminarios de la Sociedad Española de Mineralogía. 7(2010-09):5-21.