BIOMATERIALS LAB MATERIAL MECHANICAL PROPERTIES Monday January 23
BIOMATERIALS LAB MATERIAL MECHANICAL PROPERTIES Monday, January 23 rd & Tuesday, January 24 th BME 245/445 – Lab 1
PRE-LAB § Sign-in § Quiz (Engler. 2006)
WEIGHT PERCENT CALCULATIONS Wt% = (Mass Solute)/(Total Solution Mass) × 100% 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
THIOL-NORBORNENE PRECURSORS PEG-Norbornene: • 2 k. D-PEG Thiol: • 2 SH • 10 k. D-PEG • 3 SH • 20 k. D-PEG • 4 SH
10 k. D-PEG + 3 SH 10 k. D-PEG formation of a crosslinked 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 § PEG 10, 000 3 SH § 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. 2. 3. 4. 5. 10 wt% PEG in DMSO (20 wt% for 2 k. D-PEG) solution is thoroughly mixed (solublize PEG) 1: 1 mole ratio of thiol-linker 10% photo-initiator by volume 40μL placed in 1 m. L syringe (tip cut off) § to create cylindrical hydrogel sample geometry 6. exposed to UV-lamp for 10 min 7. hydrogel removed and placed in DMSO
MECHANICAL TESTING § MTS system in Materials Testing Lab – 5 N load cell “Benoit Lab Test” § cyclic compression at 5 -10% elongation of gel height § 0. 1 mm/sec compression rate § Modulus calculated using 1 -4% strain range (linear)
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?
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!!!
- Slides: 12