1. Investigation of a novel optical means to measure
mechanical properties of polyethylene glycol acrylate
photopolymers
Marisa Rocha
Irvine Valley College
Advisor: Prof. Roy McCord
2. Diabetes mellitus
• 29.1 million people or 9.3% of the U.S. population have
diabetes (National Diabetes Statistics Report, 2014)
• Metabolism disorder that causes high blood sugar levels
Source: www.quora.com
4. Diabetes mellitus
• Type 1 – body does not produce insulin (10% of cases)
• Treatment: eat healthy, exercise and self-inject insulin
Source: www.diabeteseducator.org
5. Diabetes mellitus
• Type 2 – body does not produce enough insulin (90% of cases)
• Treatment: eat healthy, physically active, monitor blood
glucose and eventual medication
Source: www.kevinmd.com
6. One possible cure for Diabetes
• Implant encapsulated islet cells
• Induction of self-production and regulation of insulin
• Challenge: prevent rejection by immune system!
Source: www.dolomite-microfluidics.com
Bio-Compatible
membrane
Islet Cells
9. PEG hydrogels as bio-compatible
scaffolds
Physical and chemical
properties suitable for Tissue
Engineering:
PEG monomer content
controls:
– Diffusion coefficient
– Mechanical properties
Source: www.mckenzieillustrations.com
10. Investigation of PEGDA mechanical properties
• A convenient novel optical means
• Alternatives complicated, expensive
11. Preparation of Polymer plugs
• High and low concentrations of monomer
• Eosin Y as photoactivator
Eosin Y stained monomer disks before photopolymerization
1 inch
(25 mm)
12. Preparation of Polymer plugs
• 524nm illumination with +/- 30nm bandwidth
Photopolymerization platform with illumination + irradiance measuring photodiode
15. Optical technique to measure Elasticity
• Initial thickness
determined with
binocular
microscope
3 inches (75 mm)
One increment = 1.51 μm
16. Optical technique to measure Elasticity
• 28mm Nikon macro lens CCD camera, 800 x 600 pixels
uniform LED illumination
• Forces from 10mN to
128mN applied to plugs
between glass slides
17. Optical technique to measure Elasticity
• Area measurements
determined by
analysis of bright-
field microscope
digital images using
ImageJ software
Sample 8BE12 plug#4
18. Optical technique to measure Elasticity
Area increases as forces are applied
ImageJ software results
19. Calculating Elasticity
Applying Young’s Modulus formula
(stress / strain)
E (ε) = σ (ε) / ε
E = (F / A) / (ΔL / ΔL0)
E = F L0 / A0 ΔL
E = modulus of elasticity (N/m2 or Pa)
σ (ε) = stress = F / A (N/m2 or Pa)
ε = strain = ΔL / ΔL0 (m/m)
25. Comparison to Other Studies
• Compression Testing Devices:
Lujan. Mechanical Bioreactor.
Source: Tissue Engineering 17.3, 2011
Chan. Microplate Compression Method.
Source: Annals of Biomedical Engineering 36, 2008.
26. Works Cited
• Bahney, C. S. et al. “Visible Light Photoinitiation of Mesenchymal Stem Cell-Laden
Bioresponsive Hydrogels”. Eur Cell Mater 22 (2011): 43–55. Print.
• Chan B. P. et al. “A Microplate Compression Method for Elastic Modulus
Measurement of Soft and Viscoelastic Collagen Microspheres”. Annals of
Biomedical Engineering 36 (2008): 1254-1267. CrossRef. Web.
• Corbin, Elise A. et al. “Micromechanical Properties of Hydrogels Measured with
MEMS Resonant Sensors”. Biomedical Microdevices 15.2 (2013): 311-319. CrossRef.
Web.
• Drira, Zouheir, and Vamsi K. Yadavalli. “Nanomechanical Measurements of
Polyethylene Glycol Hydrogels Using Atomic Force Microscopy”. Journal of the
Mechanical Behavior of Biomedical Materials 18 (2013): 20-28. CrossRef. Web.
• Gabler, Stefan et al. “Determination of the Viscoelastic Properties of Hydrogels
Based on Polyethylene Glycol Diacrylate (PEG-DA) and Human Articular Cartilage”.
International Journal of Materials Engineering Innovation 1.1 (2009): 3-20. Print.
• Lujan, Trevor J. et al. “A Novel Bioreactor for the Dynamic Stimulation and
Mechanical Evaluation of Multiple Tissue-Engineered Constructs”. Tissue
Engineering 17.3 (2011). CrossRef. Web.
