Biological materials introduction Flashcards
(33 cards)
Def. Biological material
Material produced by biological systems, natural materials
Def. Biomaterial
A material for implantation or incorporation in a living organism, can both be synthetic and biological for biomedical application
Def. Biocomposite
A composite structure tat is constructed of partly/completely of natural materials
Def. Biomimetics
Imitation of a system from nature, bio-inspired (for solving an engineering problem), does not have to be a biological material
How is biological materials often formed and under which conditions?
Formed by self-assembly, most often bottom up, in mild conditions, in ambient temperature and pressure and aqueous conditions.
Some typical properties of biological materials
- Multi-functional: serve many purposes (e.g. bone)
- Hierarchy: Different organized scale levels.
- Hydration: Properties often dependent on hydration i.e level of water in the structure. Usually hydration decease strength and increase toughness.
- Self-healing capacity
Name some pros for why using biological materials
- Sustainability: renewable, biodegradable
- Structure: multi-phase materials, hierarchically organized
- Performance: Often better than man-made, interact with water
- Manufacturing: In room temp. without solvents, minimum energy consumption
Name some non-mineralized “soft” structures
Typically fibrous constituents
- Collagen (bone, dentine, blood vessels)
- Keratin (hair, horn)
- Chitin
- Cellulose, heicellulose
- Elastin (skin, lungs, artery walls)
Name some mineralized “hard” structures
Typically consisting of hierarchically assembled composites of minerals and organic fibrous components
Minerals: Hydroxyapatite, Calcium carbonate, amorphous silica
Fibrous components: collagen and chitin
What mechanical pros does spider silk have
extremely strong and tough
What mechanical pros does shells and bone have
Extremely tough
Whats the weakness of minerals vs. biopolymers
Tension vs. compression
What defines Young’s modulus
Longitudinal stress divided by the strain
Mechanical performance of biominerals
high stiffness, low toughness, linear stress-strain plot
Mechanical performance of biopolymers
J shaped stress-strain plot, strong and extensible (high tensile strength), high toughness, low young’s modulus
Mechanical performance of composites
high toughness
Mechanical performance of foams
compressible
Name a common bioplymer
Collagen (tendon, ligaments, skin and bone)
Whats the hierarchical level of collagen 1
poly-peptides - tropocollagen - fibrils - fibers - fascicles (bundle)
Describe the stretching of spider silk
low level: amorphous strands are straightened
higher level: the crystalline beta-sheets sustain the load
What makes the bioelastomer whelk egg case strong/tough
Native state is alpha-helices but when stressed by strain they are extended and eventually oriented into strong beta-sheets
What defines thoughness
The amount of energy a material can absorb before it fails
What makes nacre so though
It has growth layers/tiles with mineral bridges between. If a crack occur it has to travel around the tiles instead of through. The tiles also have a rough surface which creates frictional resistance.
What makes the lobsters exoskeleton so though?
Have a twisted plywood structure of chitin. The layers of chitin are mineralized and cracks cannot follow a straight line, thereby increasing the toughness. The minerals fracture and the chitin fibers absorbs the strain. There is no physical separation which means self-healing can take place.
