b iomaterials l ab m aterial m echanical p roperties
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B IOMATERIALS L AB M ATERIAL M ECHANICAL P ROPERTIES. Monday, January 23 rd & Tuesday, January 24 th. BME 245/445 – Lab 1. P RE-LAB. Sign-in Quiz (Engler. 2006). W EIGHT P ERCENT C ALCULATIONS. Wt % = (Mass Solute)/(Total Solution Mass) × 100%. Determine total mass solute - PowerPoint PPT PresentationTRANSCRIPT
BIOMATERIALS LAB MATERIAL MECHANICAL PROPERTIES
Monday, January 23rd & Tuesday, January 24th
BME 245/445 – Lab 1
PRE-LAB
Sign-in Quiz (Engler. 2006)
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%
THIOL-NORBORNENE PRECURSORS
Thiol:•2SH
•3SH
•4SH
PEG-Norbornene:•2kD-PEG
•10kD-PEG
•20kD-PEG
10kD-PEG + 3SH
3SH
10kD-PEG
formation of a cross-linked mesh network
THIOL-ENE POLYMERIZATION
1 Arm
PEG(n=56)
Norbornene
Fairbanks, B.D. Adv Mater. 2009
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 ?
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
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
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)
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?
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!!!