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EBME 306 MIDTERM 2 QUESTIONS AND ANSWERS
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EBME 306 MIDTERM 2 QUESTIONS AND ANSWERS
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Name: Score:143 Multiple choice questions
Term 1 of 143
Explain polymer fatigue.
- Giant interconnected polymer macromolecules.
- Cross-linking usually results from chemical reaction in presence of chemical or thermal
initiator.
- Once cross-linked, interchain mobility is severely restricted by covalent bonds,
resulting in thermosets.
- Deformation/failure behavior of polymer under cyclic stress-strain loading; can be
considered as material becoming "tired" at stress-srain values less than ultimate stress-
strain.
- Typically expressed in terms of the number of cycles to failure.
- Fatigue test, upper stress level is always set much lower than ultimate tensile value.
- Important for most polymeric biomaterials as they undergo cyclical loading.
- Alginate composition changes depending on its MW and ration between M and G
blocks. Different ratios lead to different properties when cross-linked with calcium ions.
- G blocks have more affinity to calcium ions than M blocks. This difference influences
the permeability of alginate capsules to low MW compounds.
- Alginate with high M:G leads to more permeable alginate matrices.
- Alginate with low M:G leads to stronger structures due to the larger affinity of G blocks
with calcium ions.
- Secondary ion mass spectrometry (SIMS) is more suitable for surface chemistry
analysis
- Gives convincing data for simple aqueous soluble or organic soluble homopolymers
but becomes difficult for complex co-polymer analysis.
,Term 2 of 143
What is special about the squidbeak in relation to bio-mimicry?
The beak of the giant squid is comprised of a seemingly single composite material, but
has graded changes in stiffness between soft tissue interface to the stiff beak so as to
avoid the harsh transition and reduce failure rates.
- Change in heat capacity with increasing temperature gives info about polymer's
thermal transition and percent crystallinity.
- Estimation of heat of crystallization and total heat of melting from plot gives a way to
find %.
Polymers, thin films, assembled monolayers, surface-adsorbed structures. Gets more
info than ESCA but is less surface sensitive.
Both brittle and ductile; depends on temperature.
Term 3 of 143
gel permeation chromatography (GPC)
- Eliminates need for follow-up surgery to remove material since it is degraded,
metabolized, and resorbed.
- Cannot get naturally replaced by regrown tissue.
- Can release therapeutics while degrading.
Measurements:
- Refractive index: most common; gives concentration-sensitive (Mn) comparative data.
- Viscocity: intrinsic viscocity, Mw-sensitive and branching info.
- Light scattering: Mw-sensitive and branching info.
- Giant interconnected polymer macromolecules.
- Cross-linking usually results from chemical reaction in presence of chemical or thermal
initiator.
- Once cross-linked, interchain mobility is severely restricted by covalent bonds,
resulting in thermosets.
The sea cucumber is able to rapidly and reversibly stiffen its dermis to expose a stiff
spiky surface by regulating the interactions among collagen fibrils. This principle is
being applied to brain device insertion.
,Term 4 of 143
Explain covalent cross-linking.
- Giant interconnected polymer macromolecules.
- Cross-linking usually results from chemical reaction in presence of chemical or thermal
initiator.
- Once cross-linked, interchain mobility is severely restricted by covalent bonds,
resulting in thermosets.
Measurements:
- Refractive index: most common; gives concentration-sensitive (Mn) comparative data.
- Viscocity: intrinsic viscocity, Mw-sensitive and branching info.
- Light scattering: Mw-sensitive and branching info.
- ECM-mimetic poly(ethylene glycol) hydrogels engineered to regulate smooth muscle
cell proliferation in 3D.
- Bio-mimetic engineering of non-adhesive glycocalyx like surfaces using
oligosaccharide surfactant polymers. Prevent biofouling by preventing adhesion to
biomedical device.
- Impingement of X-rays results in the release of core electrons as photo-electrons
whose kinetic/binding energy can be measured and mapped to the parent element.
- Very useful for elemental analysis of polymer surfaces and coatings.
Term 5 of 143
polydispersity index
Analyzing Samples (cell Material) At Micron Level.
Copolymerized Heteropolymer
Maximum Elongation That Polymer Can Undergo Without Plastic Deformation.
Mw/Mn
, Term 6 of 143
What is special about the woodpecker in relation to bio-mimicry?
Advantages: biofunctionality, biodegradable, less inflammatory
Disadvantages: mechanical properties, stability, processing, immunogenicity, endotoxins
The woodpecker slams its head against tree trunks without causing injury. They do so by
constricting the jugular vein with their tongue to modulate intracranial pressure, thereby
increasing the blood volume retained in the brain.
- Mechanical (bulk stiffness and flexibility; surface topography; size and form factor)
- Chemical (managing protein corona; bioactive surfaces; antioxidants and free-radical
scavengers)
- Electrical (ionic conductors; flexible conductors; electrically-responsive materials)
- Living/dynamic (cell-seeded scaffolding; tissue ingrowth; biodegradable systems)
- Degraded products released within body can induce toxic, immunogenic, and/or
inflammatory response.
- Rate needs to be controlled for control or desired biofunction.
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