C OLLIGATIVE P ROPERTIES OF S OLUTIONS 14.4: Pgs. 498 - 504.
B IOMATERIALS L AB M ATERIAL M ECHANICAL P ROPERTIES
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Transcript of B IOMATERIALS L AB M ATERIAL M ECHANICAL P ROPERTIES
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BIOMATERIALS LAB MATERIAL MECHANICAL PROPERTIES
Monday, January 23rd & Tuesday, January 24th
BME 245/445 – Lab 1
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PRE-LAB
Sign-in Quiz (Engler. 2006)
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WEIGHT PERCENT CALCULATIONS
1. Determine total mass solute
2. Determine mass PEG
3. Determine mole ratio of PEG MOLECULE to Thiol MOLECULE, using number of reactive species each & molecular weight
4. Solve for mass/vol of each
Wt% = (Mass Solute)/(Total Solution Mass) × 100%
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THIOL-NORBORNENE PRECURSORS
Thiol:•2SH
•3SH
•4SH
PEG-Norbornene:•2kD-PEG
•10kD-PEG
•20kD-PEG
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10kD-PEG + 3SH
3SH
10kD-PEG
formation of a cross-linked mesh network
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THIOL-ENE POLYMERIZATION
1 Arm
PEG(n=56)
Norbornene
Fairbanks, B.D. Adv Mater. 2009
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SECTION 1
Influence of precursors on end-stage mechanics
Look at different PEG-thiol combinations, constant polymerization time
Measure young’s modulus of resulting network Make connections between precursors and mechanics
Number of “arms” Mesh size Steric hindrance ?
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SECTION 2
Determine network growth mechanism
PEG10,000 3SH Look at how network develops over time
Step-growth polymerization? Chain-growth polymerization?
Network “interaction” is related to observed mechanics
Step-Growth Polymerization. Wikipedia. 2011
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HYDROGEL SYNTHESIS
1. 10wt% PEG in DMSO (20wt% for 2kD-PEG)
2. solution is thoroughly mixed (solublize PEG)
3. 1:1 mole ratio of thiol-linker
4. 10% photo-initiator by volume
5. 40μL placed in 1mL syringe (tip cut off) to create cylindrical hydrogel sample geometry
6. exposed to UV-lamp for 10min
7. hydrogel removed and placed in DMSO
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MECHANICAL TESTING
MTS system in Materials Testing Lab – 5N load cell
“Benoit Lab Test” cyclic compression at 5-10% elongation of gel height 0.1mm/sec compression rate Modulus calculated using 1-4% strain range (linear)
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SECTION 3Investigate Tensile Properties & Fracture of Biomaterials
Load sample into PASCO stress/strain apparatus Begin data collection, steadily turn handle to apply tension Once bar breaks, stop data collection and remove sample Export data to Excel for post-lab calculations
Expected vs. observed behavior for each material
Take image of fracture site using stereo microscope Observed differences in fracture mechanics?
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Safety
General Lab glasses, gloves, closed toed shoes No food, no drinks, no applying makeup
Specific DMSO: Eye, skin irritant; ingestion leads to nausea,
vomiting, diarrhea, central nervous system damage Thiols: Eye, skin, respiratory irritant; cause nausea,
headache, vomiting; unpleasant smell Use in HOOD!!!