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

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 | PVA mm PVA Sample Young’s Modulus: 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: MPa

Mechanical Properties | PVA Young’s Modulus: 0.83 MPa Young’s Modulus: MPa 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.org cdn.iopscience.com

Abaqus | CAD & Simulation Software ●Use Abaqus to simulate different PVA thicknesses and nanoporous membrane dimensions o Hypothetically testing bending in 37°C DI water

Actual Testing U shape X200

M-Shaped Structure Abaqus SimulationTesting (3 cm x 6 cm)

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, ●Hassan, C. Peppas, Nikolaos. (2000, February 8). Structure and Morphology of Freeze/Thawed PVA Hydrogels. Macromolecules, 33,