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B IOMATERIALS L AB M ATERIAL M ECHANICAL P ROPERTIES

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

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B IOMATERIALS L AB M ATERIAL M ECHANICAL P ROPERTIES

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  1. BIOMATERIALS LABMATERIALMECHANICAL PROPERTIES Monday, January 23rd & Tuesday, January 24th BME 245/445 – Lab 1

  2. PRE-LAB • Sign-in • Quiz (Engler. 2006)

  3. WEIGHT PERCENT CALCULATIONS Wt% = (Mass Solute)/(Total Solution Mass) × 100% • Determine total mass solute • Determine mass PEG • Determine mole ratio of PEG MOLECULE to Thiol MOLECULE, using number of reactive species each & molecular weight • Solve for mass/vol of each

  4. THIOL-NORBORNENE PRECURSORS • PEG-Norbornene: • 2kD-PEG • 10kD-PEG • 20kD-PEG • Thiol: • 2SH • 3SH • 4SH

  5. 10kD-PEG + 3SH 3SH 10kD-PEG formation of a cross-linked mesh network

  6. THIOL-ENE POLYMERIZATION 1 Arm PEG (n=56) Norbornene Fairbanks, B.D. Adv Mater. 2009

  7. 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 ?

  8. 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

  9. HYDROGEL SYNTHESIS • 10wt% PEG in DMSO (20wt% for 2kD-PEG) • solution is thoroughly mixed (solublize PEG) • 1:1 mole ratio of thiol-linker • 10% photo-initiator by volume • 40μL placed in 1mL syringe (tip cut off) • to create cylindrical hydrogel sample geometry • exposed to UV-lamp for 10min • hydrogel removed and placed in DMSO

  10. 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)

  11. SECTION 3 Investigate 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?

  12. 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!!!

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