Biomaterials

Produced by living orgnisms

  • bones, teeth, spines, shells

Categories

  • Biomimicing
  • Biocompatible
    • Ti-implant
  • Bioinert
    • SiO\(_2\)
    • Stainless steel
  • Bioactive
    • Apatite

Last three are just materials interacting with biologicals, but biomimicing try to replicate biocreations

Biomineralization

The mechanism by which biological creatures create inorganic solids. Differences between “natural” and man-made analouges:

  • Exceptional control over shape, zise and orientation
  • Not formed corresponding to thermodynamic or kinetic control (as abiogenic materials is)
  • Extreme control over local environments (e.g. chemical composition)

Controlled crystal growth

  • Nucleation and growth in supramolecular confined host may result in size limitations, but would NOT control morphology.
  • Morphology can be controlled by strict control of localized chemical environment. (Ex specific surface-attaching surfactants limiting growth?)
  • Spatial localization of ion pumps in the compartment may shape growing crystal by turning on and off ion flows.

Used for

  • Mechanical properties (hardness, strength)
  • Chemical storage(Calcium storage)
  • Navigation

Examples:

  • Velcro: Biomimetic. From burrs that stuck on dog hair.
  • Shark skin: Rough enough to be used as sandpaper, same material as shark teeth. Reduces water friction.
  • Calcium dominates due to low solubility.
  • Calcium Carbonate: CaCO\(_3\), Calcite, arganite, vaterite: Exoskeletons, eggshells, corals, mollucs
  • Calcium phosphates: Endoskeletons (bones, teeth), calcium storage.
  • Calcium oxalate: Calcium storage, passive deposits in plants, calculi for excretory tracts.
  • Metal sulfates: Gravity sensors, exoskeletons,
  • Amorphous silica: defense in plants, diatom valves, sponge spicules, radiolarian tests.
  • Iron oxides: chiton teeth, magnetic sensors(compass needles in bacterias).
  • In the sea:
    • Diatoms: SiO\(_2\)
    • Alges: CaCO\(_3\)

How diatoms create silicon dioxide

  • Diatoms are:
    • Complex shape
    • Grown in cell structures
  • SiO\(_4^{2-}\) fed into cell by ion pumps, and stabilized by a cofactor in the cell.
  • Then it is precipitated through specific openings, like lithography.

How proteins is used to guide certain types of calcium carbonates

  • Templating: Proteins with charge groups corresponding to crystal structure of CaCO\(_3\).
  • Ex: “Biological epitaxy”: Collagen used to nucleate bone crystals.

Biomimetic materials chemistry

  • Difficult to mimic, extreme complexity not precedented by man.
  • Examples:
    • Microemulsion, Phospholipid vesicles, proteins
    • Reverse micells formed by surfactant-water molecules producing nanoparticles where oxides can grow

Virus to make batteries:

  • Tobacco mosaic virus (TMV) as anode material
  • TMV binds to metal electrode, thin film deposited on top for current collecting and then active material
  • Gives big surface -> high C-rates
  • But TMV becomes inert..
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