Advanced Materials and Material Characterization Part 2: Advanced Materials Prof. Dr. H. P. Strunk Master Materials Science course in 1st and 3rd semester WS 2013/14 Chapter 3 3.0 Outline 3. Biological materials, concepts, principles 3.1 Biological materials: product/remains of living cells by reactions and/or metabolism wood, bone, tooth, silk, resilin 3.2 Biomimetic materials: artifical materials purposely produced functional surfaces mimiking nacre (shell) 3.3 Biological concepts: preparation of artifical materials to imitate properties optimized by nature self cleaning (lotus effect), minimization of resistance (shark and dolphin skin), maximization of attachment force (insects, reptiles, gecko) 3.0 Outline
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Advanced Materials and Material Characterization
Part 2: Advanced Materials
Prof. Dr. H. P. Strunk
Master Materials Science course in 1st and 3rd semesterWS 2013/14
Chapter 3
3.0 Outline
3. Biological materials, concepts, principles
3.1 Biological materials: product/remains of living cells by reactions and/or metabolism
wood, bone, tooth, silk, resilin
3.2 Biomimetic materials: artifical materials purposely produced
functional surfacesmimiking nacre (shell)
3.3 Biological concepts: preparation of artifical materials to imitate propertiesoptimized by nature
self cleaning (lotus effect), minimization of resistance (shark and dolphin skin), maximization of attachment force (insects, reptiles, gecko)
3.0 Outline
line split intoplants, fungi,mamals
3.0 Outline
3. Biological materials, concepts, principles
3.0 Outline
The materials scientist's view onearth history:
Cryogenian Period850–635
great extinction
065
150
200
275
400
465
500550
line split intoplants, fungi,mamals
3.0 Outline
3. Biological materials, concepts, principles
3.0 Outline
first plants on land
Cambrian explosion
insects, plants withwoody stems
dinosaursammonites
mineralizedexoskeletontrilobites
archeopterix
great extinction
The materials scientist's view onearth history:
cynodonts
first bones in jawless fish
Cryogenian Period850–635
time line for thedivergence of animals, plants, and fungi. This treehas a radial time scaleoriginating about 1100 million years (my) ago withthe last common ancestorof plants, animals, and fungi. Contempo-raryorganisms and time are at the circumference. Lengths of branches arearbitrary. The order of branching is establishedby comparisons of genesequences. The times of the earliest branchingevents are only estimates, since calibration of themolecular clocks isuncertain and the earlyfossil records are sparse.
Cell Biology 2nd edition, by Thomas D. Pollard, William C. Earnshaw, and
Jennifer Lippincott-Schwartz
Elsevier, 2007, e-book
great extinction
065
150
200
275
400
465
500550
line split intoplants, fungi,mamals
3.0 Outline
3. Biological materials, concepts, principles
3.0 Outline
first plants on land
Cambrian explosion
insects, plants withwoody stems
dinosaursammonites
mineralizedexoskeletontrilobites
archeopterix
great extinction
The materials scientist's view onearth history: materials specifications
bones light weight, highlymechanically resistant
bones stable high load bearing
teeth friction resistant, hard
organic, hard, sturdy, highly elastic fibersflexible but mechanicallystable layered structures
hard with limited flexibility
cynodonts
first bones in jawless fish
Cryogenian Period850–635
3.0 Outline
3. Biological materials, concepts, principles
3.0 Outline
Classifications
Preparation Structure and Physics Properties
Methods of preparationby‐product due to pH changesdead end product of metabolismHybrid materials
Task of the master course'Nano‐Compound Materials'
next summer semester(Prof. Bill)
our job now mostly mechanical properties
electrical/optical propertiesonly every now and then,
fibrous space‐filling mixture of proteins supportive, rigidmostly proteins mostly sugars and polysaccharides brittle properties
collagen polysaccharides, whole variety of very versatileamino acid chains proficient possibilities mechanical/viscoelastic due to large restricted linking in linking and branching, properties, gel, soft tissue, freedom in
fibrous space‐filling mixture of proteins supportive, rigidmostly proteins mostly sugars and polysaccharides brittle properties
collagen polysaccharides, whole variety of very versatileamino acid chains proficient possibilities mechanical/viscoelastic due to large restricted linking in linking and branching, properties, gel, soft tissue, freedom in
cellulose, chitin (+water) cartilage composition
mechanical properties and appropriate descriptions
Hook and non‐Hook viscoelastic propertiescomposite materials aspects
? fracture
3.1 Biological materials
3. Biological materials, concepts, principles
3.1 Biological materials
Mechanics, revisiting what we thought to knowHook's law
macroscopic view microscopic view
εσ
εσ
εσ
d
dE =
∆∆
==
stiffness, Young's modulus
σ
ε
shear modulus
,...γτ
=G ( )υ+=
12
EG
short range forces between atoms
ν: Poisson's ratio
acf ∆= c: spring constant∆a: change in atomic distance
2
2
02
2 11
da
Ud
ad
UdE =
Ω=
ε
3.1 Biological materials
3. Biological materials, concepts, principles
3.1 Biological materials
Mechanics, revisiting what we thought to knowHook's law and plasticity, which measure for strain and stress?
macroscopic view
0l
l∆=Cε ∆ℓ: change in length
ℓ0: initial length
true strain
ll /dd =ε concerns the actual true terms
)1ln( Ct εε +=
tε
σC,σt
σC
σt
εC
true stress σt, conventional strain εc
A0 ℓ0 = A ℓ A0/A = ℓ/ ℓ0 = 1+εC
σt = F/A = F/A0•A0/A = σC(1+εC)
plastic flow: volume is constant!
Ultimate tensile strength, conventional
0=C
C
d
d
εσ
i.e. horizontal tangent
more precisely: Considère criterion
The total load F is always
At the instability/necking point:
3.1 Biological materials
3. Biological materials, concepts, principles
3.1 Biological materials
ttAF σ=
tttt dAdAdF σσ +== 0with volume constancy:
0)( =+== lll dAdAAddV ttt
with
ttt ddAdA ε−=−= ll //
tt
t
d
d σεσ
= )1ln( Ct dd εε +=and with
C
t
C
t
d
d
εσ
εσ
+=
1
εC
σt
Mechanics, revisiting what we thought to knowHook's law and plasticity, ultimate tensile strength
tt
t
t
t dA
dAd εσσ
=−=
3.1 Biological materials
3. Biological materials, concepts, principles
3.1 Biological materials
Mechanics, revisiting what we thought to knowNon‐Hookean behavior, in view of ultimate tensile strength
σC
εC
])1(1[ 2−+−+= CCC const εεσstrain stiffening
linear, non-linear elastic
J. Vincent, Structural Biomaterials, Princeton University Press,1982,1990,2012
3.1 Biological materials
3. Biological materials, concepts, principles
3.1 Biological materials
Mechanics, revisiting what we thought to knowNon‐Hookean behavior, in view of ultimate tensile strength
σC
εC
J. Vincent, Structural Biomaterials, Princeton University Press,1982,1990,2012
striking difference between conventional andbiological materials in necking and fracture!
-1 0 1 2 3 4
σt
εC
3.1 Biological materials
3. Biological materials, concepts, principles
3.1 Biological materials
Mechanics, revisiting what we thought to knowNon‐Hookean behavior, in view of ultimate tensile strength
σC
εC
in consequence:'... nearly all biological materials have a concave stress‐strain curve .... there will belittle possibility of local increases in stress ...
σt
εC J. Vincent, Structural Biomaterials, Princeton University Press,1982,1990,2012
Polyethylen sample with a stable neckhttp://en.wikipedia.org/wiki/File:Stable_neck_MDPE.jpgdownload 8. July 2012
striking difference between conventional andbiological materials in necking and fracture!
E
E u
E r
ωτ
3.1 Biological materials
3. Biological materials, concepts, principles
3.1 Biological materials
Mechanics, revisiting what we thought to knowViscosity aspectssee Bachelor course'Structural Materials'
elastisch
elastisch
σe = E2 ε2
σv = 3ηε2
σe = E1 ε1
viskos
σ, ε
σ, εZener model
τ = τ * Er / Eu = const3ηE2
t
σ
σ1
t
ε
σ1Erσ1
Eu
Eu = E1
Er =E1E2
E1 + E2
10 ∞
⎭⎬⎫
⎩⎨⎧
⎟⎠⎞
⎜⎝⎛ −
=⎟⎠⎞
⎜⎝⎛ −
=τ
σστ
εε ttexp exp 00
actE/ητ =
unrelaxed modulus
relaxed modulus
EuEr
σ1
σ
ε
Eu
E
E u
E r
ωτ
3.1 Biological materials
3. Biological materials, concepts, principles
3.1 Biological materials
Mechanics, revisiting what we thought to knowViscosity aspectssee Bachelor course'Structural Materials'
elastisch
elastisch
σe = E2 ε2
σv = 3ηε2
σe = E1 ε1
viskos
σ, ε
σ, εZener model
τ = τ * Er / Eu = const3ηE2
t
σ
σ1
t
ε
σ1Erσ1
Eu
Eu = E1
Er =E1E2
E1 + E2
10 ∞
⎭⎬⎫
⎩⎨⎧
⎟⎠⎞
⎜⎝⎛ −
=⎟⎠⎞
⎜⎝⎛ −
=τ
σστ
εε ttexp exp 00
actE/ητ =
unrelaxed modulus
relaxed modulus
EuEr
σ1
σ
ε
Eu
time dependent elasticity modulusor relaxation modulus
3.1 Biological materials
3. Biological materials, concepts, principles
3.1 Biological materials
Mechanics, revisiting what we thought to knowViscosity aspects: time
mostly in vertebrats ashorn, hair, hoof, feather, skin
different keratin types:
mammalian, avian, reptilian
cross‐linking based on
sulfur or tyrosine,these break the helix!
amorphous regionsand oriented helices
bimodal material
rope‐like super structuresembedded in non‐fibrousmatrix like two‐phase material
wool relative humidity
same initial modulus
H‐bonds rupture and destabilize helicestowards β‐sheet fromation
final high modulus:contribution of back‐bone
Hair. wool:
3.1 Biological materials
3. Biological materials, concepts, principles
3.1 Biological materials
hierarchical structure
Structural proteins: keratin (α‐keratin)
rope‐like super structuresembedded in non‐fibrousmatrix like two‐phase material
Horn (rhinozeros)
mechanical anisotropy
very large mechanical hysteresis inhairreturn curve: helices reform
high toughness: most energyexpended for deformation is notstored and thus not availablefor fracture
covalent
3.1 Biological materials
3. Biological materials, concepts, principles
3.1 Biological materials
Structural proteins: silkfrom Bombyx mori (silk‐worm)
β‐sheet antiparallel, large part of fibre
high strength in fibre axis, backbone stretchingin‐plane H‐bondings perpendicular to backbone
ensure planar structurevan der Waals bonding permits flexibilityH‐ and v.d.Waals‐bonds transmit shear forces
a: alanine (R= H)g: glycine (R= N)
role of side groups:the more bulky the less ductile
fig 2.17
3.1 Biological materials
3. Biological materials, concepts, principles
3.1 Biological materials
Structural proteins: collagen
Most common fibregenerally in tissues,muscles (tendons)winding of pressure vessels
basis for glues and gelatins
single fibre: three 'slow' left‐handedhelices, hydrogen‐bonded
3.1 Biological materials
3. Biological materials, concepts, principles
3.1 Biological materials
Structural proteins: brief summary for fibres with preferential bonds along themolecule and fibre dominated compounds
• reasonably large range of elasticity, depends on side chains• very high elasticity moduli after a varying range of low modulus deformation• i.e. relatively high modulus and restricted extensibility• extremely anisotropic mechanical properties• regular sequence of amino acids determines the conformation, mostly helices,
by formation of hydrogen bonds and/or v.d.Waals bonds• expression of conformation reduced by water due to bond weakening
depending on structure/conformation, compounds can be very rigidand carry large tensional forces and/or
show high or low damping capabilitiesmaterials are extensible essentially due to amorphous regions in compounds
β‐turn of elastin with possible rotationsthat cause high elasticity, supported by0,4 % covalently cross‐linking amino acidsVal: valine (helix former)Gly: glycinePro: proline
Elastin: very low elastic modulus and high extensibility, reduced viscoelastic character,Resilin, Abductin: even higher elasticity because of higher content of helix breakers
3.1 Biological materials
up to 87 %64 %45 %helix breakers
abductinresilinelastin
brief summary 'protein rubbers'
• Very high extensibility at rather low elastic modulus• work best with water as plastiziser• Differences in properties due to changes in composition:
elastin: mostly for static tensile loading (head of cow,horse)resilin: mechanical energy storer in insects, flight mechanism, slow storing of
energy and fast release at start of wing stroke, or locust/flee jump• very small energy loss, 'resilience' R=1‐2πtanδ (1‐energy loss in hysteresis loop)
R(resilin) 96‐97%, avoids overheating in flying animal• abductin: properties in between, resilience lower (80 %)
β
variations in molecularsteric configuration(side view):2 boat2 chair
Three main types of pure polysaccharides: fibre, elastic gels, viscoelastic gelsinterconvertible
Fibresback bone elasticity with strong shear contributions by intermolecular H‐bonds
Cellulose
Chitin
spatial arrangement next
3.1 Biological materials
3. Biological materials, concepts, principles
3.1 Biological materials
Three main types of pure polysaccharides: fibre, elastic gels, viscoelastic gelsinterconvertible
Fibresback bone elasticity with strong shear contributions by intermolecular H‐bonds
‐‐‐‐ hydrogen bonds back bone direction
cross direction in plane cross direction in plane
α‐chitin
sheet normal
3.1 Biological materials
3. Biological materials, concepts, principles
3.1 Biological materials
Three main types of pure polysaccharides: fibre, elastic gels, viscoelastic gelsinterconvertible
Fibresback bone elasticity with strong shear contributions by intermolecular H‐bonds
Consequences of these types of conformation
1. high modulus, up to more than 100 GPa, aided by the many H‐bonds2. reduced degree of crystallinity (i.e. higher amorphous part) reduces
this modulus3. removal (inactivation) of H‐bonds (water!) reduces modulus by up to factor 44 Chitin much stiffer than cellulose,because the acetylic side chainsoffer more H‐bonds and strong steric hindrances
3.1 Biological materials
3. Biological materials, concepts, principles
3.1 Biological materials
Three main types of pure polysaccharides: fibre, elastic gels, viscoelastic gelsinterconvertible
Gelspolysaccharides with alternating 1,3 and 1,4 links
example
β 1‐3 link
3.1 Biological materials
3. Biological materials, concepts, principles
3.1 Biological materials
Three main types of pure polysaccharides: fibre, elastic gels, viscoelastic gelsinterconvertible
Gelspolysaccharides with alternating 1,3 and 1,4 links
example
1. form extended helices, intertwinedor nestled with each other
2. very stable structures in water,3. water trapped in various ways: sugar
units carry negative charges, drives the chains to an extended conformation, entrains large amounts of water, strongly(double H‐) and weakly (single H‐) bond water, trapped in compartementsformed by structure (mixture also entropically driven).
5. typical solid content of elastic gel: 2 %6. charges cause strong effects on added ions
3.1 Biological materials
3. Biological materials, concepts, principles
3.1 Biological materials
Sugars and polysaccharides
Ions like Ca2+, Na+,K+, Mg2+, can beincorporated here
••
•
•
•
see Anderson, J. Molecular Biology 1969
3.1 Biological materials
3. Biological materials, concepts, principles
3.1 Biological materials
Sugars and polysaccharides
Gels: some properties
10‐s compliance of2% alginate gel inwater, pH 6.0 as afunction of Ca2+‐citrate. Ca causes rigidity
10‐s compliance ofalginate gel in water,pH 6.0, as a functionof alginate content.compliance increaseswith alginateconcentration
compliance = ε/σ
3.1 Biological materials
3. Biological materials, concepts, principles
3.1 Biological materials
Sugars and polysaccharides
Shear stiffness (modulus)of pedal mucus (AriolimaxColumbianus) as a functionof water content.Lubrication by water veryefficient at >80 % water
mind log and scale
Gels in plants are mostly extracellularthat maintain plant's osmotic environment,give physical protection and controltransport of metabolites
Gels: some properties
property: brittle plasticH2O binding: high small
Stress‐strain curves of aragose, κ‐ and λ‐ carrageenan as 2% gels. Thedifferences in extensibility are due tothe degree of binding of the water.
Vincent 3rd ed.
3.1 Biological materials
3. Biological materials, concepts, principles
3.1 Biological materials
Sugars and polysaccharides
Fig 3.16in animals
Hyaluronic acid family of animal polysaccharides
polyuronides orglycosaminoglycansassociated with proteins
3.1 Biological materials
3. Biological materials, concepts, principles
3.1 Biological materials
Sugars and polysaccharides
Fig 3.16in animals
Hyaluronic acid family of animal polysaccharidesMolecular weight: 106 – 107 or even moreMolecule length: 2.4 m, occupies in liquid
a sphere with 1 m diameter!
Consequence: 1 g hyaluronic acid occupies 5 l.High binding capacity of water, extensive spanof mechanical properties from large stiffness(dry state), over decades of viscosity to highplasticity and liquid viscosity
3.1 Biological materials
3. Biological materials, concepts, principles
3.1 Biological materials
Sugars and polysaccharides
Fig 3.18
Real (G') (shear) modulus and imaginary (G'') (loss) modulusas a function of frequency.Hyaluronic acid. ω: oscillation frequencyThe elastic field (G') takes over at/towards larger frequencies,here around 1 kHz, i.e. essentially elastic instead of viscous behavior
Viscocity decreases withshear rate drastically
This property is relevant to lubrication,e.g in knee joints. Slow motion: elastic,fast motion: material is almostliquid and serves as lubricant.Reversible.
Hyaluronic acid family of animal polysaccharides, mucus with similar, yet much enhanced properties
3.1 Biological materials
Pedal mucus from slug Ariolimax columbianus= 'banana slug'
3.1 Biological materials
Denny 1981
3. Biological materials, concepts, principles
Sugars and polysaccharides,
Hyaluronic acid family of animal polysaccharides, mucus with similar, yet much enhanced properties
3.1 Biological materials
Pedal mucus from slug Ariolimax columbianus= 'banana slug' : saccharide plus certain amount of
protein, 'strange material' (Vincent)
3.1 Biological materials
viscoelastic properties ofmucus pomatia
low rates of deformation and strain < 0.1:viscoelastic solid, a little flow only
at high shear rate: behaves like rubbery stuff,BUT: this gel strained to ∼5, ist network breaks down
fluidic behavior! once shear stops, solid rubbery again
fast con‐traction
wave, speed say 2v
F
fluidsolidsolid solidfluid
substrate no shear force
mucus
foot ofslug
fast con‐traction
3. Biological materials, concepts, principles
Sugars and polysaccharides,
Hyaluronic acid family of animal polysaccharides, mucus with similar, yet much enhanced properties
3.1 Biological materials
Pedal mucus from slug Ariolimax columbianus= 'banana slug' : saccharide plus certain amount of
protein, 'strange material' (Vincent)
3.1 Biological materials
low deformation rates at strain < 0.1:viscoelastic solid, a little flow only
at high shear rate: strain ∼5, fluidic behavior
! shear stops, solid rubbery again
v velocity of slug
fixed
principle of slug's crawling
Note: crawling is of all existingmotional principles(swimming, flying, running)the most inefficient one
We keep in mind:
∼10 µm
3.1 Biological materials
3. Biological materials, concepts, principles
3.1 Biological materials
Combination of protein and polysaccharide fibres (soggy materials)
Model of soft tissue ('bottle brush model')
(Collagen‐proteoglycan‐hyaluronic acid model, proteoglycan in bottlebrush conformation, binds large amounts of water!)
Cartilage consists of a gel as matrixand a distribution of protein fibres, that form a dense network at the surface.Stability and rigidity due to osmotic swellingby incoming waterthat puts proteins in tensional pre‐stress.
One example only for stabilization: cartilage (rigidity from water)
observed proteinorientations
model
3.1 Biological materials
3. Biological materials, concepts, principles
3.1 Biological materials
stiff materials, fibrous composites
Remind: biological elements treated so far:
1. proteinsform fibers, layers and volume materialmechanically anisotropic behaviour, strongly governed by side chainselastic and viscoelastic properties in a wide range: frompurely elastic with high elastic modulus to highly damping
2. polysaccharidesform fibres, due to very many interactions very large spectrumof mechanical properties
esp. gel forming by water incorporation to very large percentages, and spectrum from elastic to stiff, velocity dependent
sensitive to pH and metal ions
3. Combinations: hard, elastic, viscous materials, easy‐to‐change between
3.1 Biological materials
3. Biological materials, concepts, principles
3.1 Biological materials
stiff materials, fibrous composites
voigt-reuss Fig 5.5 Fig 5.1 Teil 4,5
Remind: important biological elements treated so far:
1. strong fibre structures: proteins2. variably strong matrix/volume structure: polysaccharides with water
Treatment of their composites with classical fibre strengthened materials