Biomedical Engineering Reference
In-Depth Information
measuring the stress-strain behavior of a bulk matrix comprised of
nanoscopic electrospun fibers, other methods must be employed.
The computational method known as finite element analysis (FEA)
is an attractive approach to developing a detailed understanding of
the nanolevel and microlevel strains generated by tissue-level phys-
iologic forces. Stylianopoulos and Barocas
68
developed a structural
model that uses volume-averaging theory to study the mechanical
behavior of fibrous collagen networks. The model represented the
network microstructure as a three-dimensional, fibrillar network
andaccountedforthethreedimensionalityandheterogeneityofthe
network, the interaction among the collagen fibers, and the realign-
mentofthefibersupontheapplicationofstress.Themodelsuccess-
fullypredictedmechanicalfeaturesoffibrouscollagennetworkslike
thePoissoneffect,theeffectofnetworkheterogeneityonthemacro-
scopic deformation field, and the realignment of the collagen fibers.
Their model did not account for the presence of cells or interstitial
fluid in a tissue equivalent, which largely contribute to tissue vis-
coelasticity.
Stella
et al
.
69
combined computation and experimentation to
study deformation mechanics of cell-seeded electrospun scaffolds.
They electrospun polymer fiber scaffolds while simultaneously
electrospraying viable vascular smooth muscle cells. The scaf-
folds were subjected to controlled biaxial stretch with three-
dimensionalcellulardeformationsandlocalfibermicroarchitecture
simultaneously quantified. They demonstrated that the local fiber
geometryfollowedana
nebehaviorsothatitcouldbepredictedby
macro-scaffolddeformations.However,theyfoundthatlocalcellular
deformations depended nonlinearly on changes in fiber microarchi-
tecture and ceased at large strains where the scaffold fibers com-
pletely straightened.
15.7 Conclusions
Rationally designed electrospun meshes are intrinsically complex
structures that exhibit controlled properties at the nanometer-,
micron-, and millimeter-length scales. In this chapter strategies
to control the meshes at these three length scales, including
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