• Hybrids made by plants or animals
• Strong composites from very weak components
– Wet protein and carbohydrates are very soft
– calcium carbonate is also weak and soft
• Multiple phases, hierarchical structures

Animals
Organic phase is biopolymers
Nacre
Plants
Argonite (CaCO
3
) plates as inorganic with protein (polyamide) as organic phytolith
Teeth, spines in echinderms
Mussel shells, sponges, diatoms and corals are utilize hybrid organic-inorganic materials
Carbohydrates are the template and organic phase

In materials, a structure with different structures at different length scales: like in tendons (above)

The Building Plan
Fabrication Conditions in Living Organisms only few elements: C, H, O, N, P, S, Ca, Si, Mg mild pH ambient pressure and temperature
Calcite Crystals Extracted from the Prismatic Layer of Pinna Nobilis Shells www.cutgana.it/acquario/specie Marin et al ., J. Biol. Chem., 2005 , 40, 33895

The Building Plan
Fabrication Conditions in Living Organisms only few elements: C, H, O, N, P, S, Ca, Si, Mg mild pH ambient pressure and temperature
Interaction of an Organic and an Inorganic Component
Incorporation of biopolymers  increased fracture resistence
&
Hierarchical Design – Morhpology
Control on Several Levels chitin network aspartate residue in peptide bond
Nudelman et al .,
Faraday Discuss.
2007 , 136, 9

Colloidal silica in diatoms: Hierarchical structure pH ≈ 5
Silica walls are build up from ca. 5nm particles to give ca. 40nm diameter particles that are organized within the frustule.

Silica (SiO
2
) & protein radiolaria diatoms
Proteins act as templates for building silica architectures

Bio-Hybrids based on CaCO
Argonite (CaCO
3
3
) plates as inorganic phase
: Nacre with protein (polyamide) as organic phase
Fracture strength is
Mother-of-pearl
3000 times higher than its mineral constituent CaCO
3
.
Opalescence from light diffraction in nacre
(argonite blocks height
≈ λ light)

The hierarchical structure of nacre
Macromolecular
Growth rings
(mesolayers)
The shell itself
Phase morphology
Inner surface of shell (mother or pearl)
Long range order: stacked crystals
Barthelat F Phil. Trans. R. Soc. A 2007;365:2907-2919 argonite crystal structure

Lobster exoskelton
CaCO
3
& Carbohydrate & protein

Apatite – hydrated CaPO
4
Protein– collagen & others

The layered, rod structure of hydroxyapatite (a calcium phopshate) in dental enamel. Very tough for a ceramic.

Hierarchical structure of alligator gar, a primitive fish, scales. Ganoine is mostly mineral, like enamel, with tougher bone beneath.

Regular Fish Scales
Enamel and collagen

fish scales are better than polycarbonate.
note how they give, and then reload. This is just one scale.

Apatite – hydrated CaPO
4
Protein– collagen
200 MPa yield strength 30 MPaM 0.5 toughness

The Building Plan
Fabrication Conditions in Living Organisms only few elements: C, H, O, N, P, S, Ca, Si, Mg mild pH ambient pressure and temperature
Interaction of an Organic and an Inorganic Component
Bone
&
Hierarchical Design – Morhpology
Control on Several Levels structural optimization from the atomic to the macroscopic scale
Peterlik et al ., Nat. Mat., 2006
Gupta et al ., PNAS, 2006
Fratzl et al ., Progr. Mat.
Science, 2007

CaCO
3
Protein templating

SiO
2 silica
2-3% silicon by weight
Horsetail, banana leaves

hierarchical structures
Templated by proteins

Euplectella sp.
 7 hierarchical levels
Stress-deflection responses of synthetic silica rod and sponge spicule in flexuretesting. (Courtesy of M. Sarikaya and G.
Mayer.)

conch shell
Almost no protein
3 hierarchical levels of layers made from layers of calcite.

the tips of the teeth are hard magnetite
(Fe
3
O
4
) with a tough fibrous calcite interior

carbohydrate fibers in a protein matrix with zinc and magnesium ions
Politi, Y., Priewasser, M., Pippel, E., Zaslansky, P., Hartmann, J., Siegel, S., Li, C., Barth, F. G. and Fratzl, P.
(2012), A Spider's Fang: How to Design an Injection Needle Using Chitin-Based Composite Material. Adv.
Funct. Mater., 22: 2519 –2528

Biomaterial: Toucan Beak
(a) Toucan beak; (b) external shell made of keratin scales.
Cellular materials: (a) synthetic aluminium foam; (b) foam found in the inside of toucan beak.(Courtesy of M. S. Schneider andK. S. Vecchio.)

Sophisticated, highly evolved hybrids
-nominally weak, but bio-accessible minerals (eg. CaCO
3
)
-hydrophilic, water plasticized biopolymers (eg. protein)
-Integrated at nano-length scales
-Phase separation templating of hierarchical structures
-All water based chemistry!! The ultimate green chemistry
Optimized to give non-additive property (synergistic effects)
Models for many research programs in hybrid materials