| Date post: | 12-Jan-2016 |
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Creating Actuated Self-folding Tissue Scaffold Architectures Based
on Nanoporous Membranes
Megi Maci, YSP Student, Quincy High School
Camilo Gonzalez, YSP Student, Revere High School
Professor Carol Livermore, Mechanical and Industrial Engineering, Northeastern University
Goal
● Creating liver tissue to save lives○ Increase supply of organ
transplants○ A tool for screening new
medical therapies
ladiesgadgets.com
Liver | What Does It Do?
● Processes and stores body’s nutrients● Purifies and expels toxins from bloodstream (e.g. ammonia)● Urea carried to kidneys → ureters → bladder → body fluid
gi.jhsps.org
Why Origami?
● Replicate the repeating subunits of the liver (lobules)
embryology.med.unsw.edu illuminationstudios.com
Scaffold Design | Accordion Fold
Blue = Hepatic Cells | Red = Endothelial Cells
● Start from accordion folded channels (easier to fold)● PURPOSE: folded channel offers more functional area
Folded Structure Based on Nanoporous Membrane
PVA
PVA
PVA
Polyvinyl Alcohol (PVA)
● Biocompatible● Friendly with nanoporous
membrane● A hydrogel produced by
repeated freeze-and-melt cycles● Swells fast in water● Dissolves slowly in water● Dries fast in air
1. 15% PVA solution (90°C deionized water)
2. Mold or spin-coat PVA layers | silicon wafers and petri dishes
3. Freeze all samples at -20°C for 10 hours
4. Thaw all samples for 2 hours at room temperature
Making PVA
Making PVA | (Continued …)
6. Store polymerized PVA in vacuum-sealed Ziploc bag at 0°C5. Repeat steps 1 through 4 (3 cycles in total)
(3 cycles = optimum tensile strength after repeated freezing and thawing; after that = levels off)
Mechanical Properties | PVA● Young’s Modulus: measure materials’ ability to withstand changes
in length when undergoing uniform tension or compression
mbari.org
Mechanical Properties | PVA2.467 mm PVA Sample
Young’s Modulus: 0.0051 MPa
Young’s Modulus varies with and is dependent upon different PVA thicknesses and the amount of time spent in the freezer and thawing.
Young’s Modulus: 1.235 MPa
Mechanical Properties | PVA
Young’s Modulus: 0.83 MPaYoung’s Modulus: 1.647 MPa
0.521 mm PVA Sample
● Measuring stress (MPa) as a function of strain● Measure angle of bending - neutral plane● PVA expands in water, but nanoporous membrane does not
Why Can It Fold?
cdn.phys.orgcdn.iopscience.com
Abaqus | CAD & Simulation Software● Use Abaqus to simulate different PVA thicknesses and nanoporous
membrane dimensionso Hypothetically testing bending in 37°C DI water
Future Extensions
● Find the most effective and efficient tissue origami structure● Lodge hepatic and endothelial cells along the nanoporous
membrane● Synthetic liver
cdn.weedemandreap.com
Acknowledgments
● Claire Duggan● Carol Livermore● Sanwei Liu● Tian Liu● Majid Bigdeli● Xin Xie● Maureen Cabrera
WHAT ARE THOSE?!?
● Chenye Yang
● Josh Miranda
● Diana Cost
● James Carroll
● Gabriel Fernandez
● Madeline Leger
Works Cited
● Hassan, C. M. Peppas, N. A. (2000). Structure and applications of poly(vinyl alcohol) hydrogels produced by conventional crosslinking or by freezing/thawing methods. Advances in Polymer Science, 153, 38-62.
● Hassan, C. Peppas, Nikolaos. (2000, February 8). Structure and Morphology of Freeze/Thawed PVA Hydrogels. Macromolecules, 33, 2472-2479.
