Scaffold Fabrication Flashcards
What is the advantage and disadvantage of fiber mesh technique
advantage= provide a large surface area for cell attachment and rapid diffusion nutrient that is favorable for cell survival and growth
disadvantage= lack of structural stability
describe the process of selective laser stintering
- Uses focused laser beam to fuse loosely compacted powder.
- Layer of powder is spread over flat surface
- Powder that is struck by laser material is fused while other areas of material remain dissociated
- Successive layers of powders are deposited and fused on top of one another until the entire part is complete
define open cell metal foams
pores form inter-connected network, typically used in aerospace
closed cell metal foams
used as impact absorbing material
Describe two methods for producing metallic foams
-foaming melts by gas injection
• Silicon-carbide, aluminum-oxide, or magnesium-oxide particles are used to enhance the viscosity of the melt.
• First step is preparation of an aluminum melt containing one of these substances and it is foamed by injecting gases
• Resultant viscous mixture floats up to the surface of the liquid and is allowed to solidify
• Average pore size: 5 mm to 20mm
-foaming of melts with blowing agents
• Melt is stirred to increase viscosity by the formation of calcium oxide (CaO), calcium-aluminum oxide (CaAl2O4) – Calcium metal is added to an aluminum melt at 680°C
• Titanium hydride (TiH2) is added serving as a blowing agent
• After cooling the vessel below the melting point of the alloy, the liquid foam turns into solid aluminum foam
• The foams produced in this way seem to be the most homogeneous – aluminum foams
• Average pore size ranges between 2mm and 10mm
State and describe four methods to fabricate polymeric scaffolds for tissue engineering
solvent casting-polymeric solution is added into mold for desired shape, solution is then dried off and polymeric membrane is than created which adheres to the mold
particulate leaching-salt, wax, or sugars (such porogens) are used to create the pores or channels. These poregens are pored into the mold and a polymer solution is then casts into the salt filled mold. after the evaporation of the solvent, the salt crystals are leached away using water to form the pores of the scafold.
-gas foaming- uses high pressure carbon dioxide gas for fabrication of highly porous scafolds, steps, the polymer is saturated with gas, pore nucleation is created by phase separation, afterwards porous structure is created
gas foaming+particle leaching
melt molding- PLGA powder and gleatin microspheres fill a teflon mold. there are heated above glass transition temerpature so particles attach to each other, then the gelatin microspheres are disolved by imersing the mixture into water and scaffold are then dried.
3D printing
knitting and braiding- individual fibersor yearns may be woven knitted or braided into patterns iwth variable pore sizes
freeze drying- polymer is dissolved ina solvent to form a solution of desired concentration, solution is frozen and solvent is removed by rducing the surround pressure to allow the frozen water in the material to sublimate directly from the solid phases to the gas phase
the amount of void space within a scaffol’s strucutre refers to the materials poresity/pearmeability
porosity
porosity/permeability is a measure of the ease with which a fluid can flow into and through a structure
permeability
what is melt molding
PLGA powder and gelatin microspheres are filled into a teflon mold. it is then heated with pressure, above glass transition temperature, so that the particles attach to each other. . the gelatin microspheres are than removed through immersion in water and pores are than created through this.
describe process for electrospinning
Electrospinning is a fiber production method which uses electric force to draw charged threads of polymer solutions or polymer melts up to fiber diameters in the order of some ten nanometers.
describe a process to make cermaic scaffolds
selective laser sintering- uses focused laser beam to fuse loosely compacted powder. powder that is strucut by laswer material is fused while other ares of material remain dissociated. successive layers of powders are deposited and fued on top of one another until the entire part is complete
