BIOE 2010 Week 2 Notes
BIOE 2010 Week 2 Notes BIOE 2010
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This 4 page Class Notes was uploaded by Sara Littlejohn on Thursday September 1, 2016. The Class Notes belongs to BIOE 2010 at Clemson University taught by Dr. Alexis and Dr. Webb in Fall 2016. Since its upload, it has received 12 views. For similar materials see Intro to Biomedical Engineering in Bioengineering at Clemson University.
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Date Created: 09/01/16
Biomaterials Continued Biodegradation: chemical degradation of a material resulting for the activity of a biological agent Bioerodible: a water-insoluble material that is converted under physiological condition into water soluble material without regard to a specific mechanism The most common polymers are called polyesters. - The ester bond can be broken down by water or enzymes Factors Governing Degradation - Chemical composition o Molecular weight High molecular weight polymer degrades slower because there is more to be degraded o Crystallinity Sections of the polymer are called oligomers. An oligomer is water soluble so now they can diffuse out and into the water, causing a loss in mass. A crystalline polymer degrades slower because it is very difficult for water to enter the structure and react with the polymer due to its unorganized structure. o Hydrophilicity/Hydrophobicity Hydrophobic polymer degrades slower because it repels water (the water can’t get to the polymer to start the reaction) - Geometry Natural Polymers as Biomaterials - Typically degrade quickly - To change the degradation properties, it requires some kind of chemical reaction o To do this people usually use cross-linking - Examples: o Collagen o Hyaluronic Acid Lubrication Wound healing o Chitosan Wound healing o Cellulose Plant polysaccharide Filtration membranes Polymer Synthesis - Addition Polymerization o Chain reaction o Initiation involves a chemical o Double bonds are usually involved in this reaction - Condensation Polymerization o Formation of a covalent bond o Release of a small molecule o Some chemical can be used to stop the reaction Mechanical Forces/Loading - Tension: force from different directions - Compression: force in the same directions - Shear: opposing directions - Bending: combination of tension and compression - Torque: twisting in opposite directions Stress-Strain Curve - As stress is applied width decreases and length increases - If you increase force, you increase the length - Modulus of elasticity (Slope of the Stress-Strain curve) - Stresses and Strains can be: o Elastic: recoverable deformation o Plastic: permanent deformation o Viscoelastic: time-dependent deformation Polymer Processing - Molding o Compression Molding Can cause defects Can’t make fibers o Injection Molding: More precise and clean than compression molding No defects Can’t make fibers o Blow Molding Allows you to have a hollow sample unlike the previous two methods - Extrusion o Can make fibers o Types: Melt Spinning Fibers Starts with polymer chips Dry Spinning Fibers Starts with a polymer solution - Machining o Micromachining Must be done in a controlled environment because the material produced is so small even dust can ruin the process Micromolding is typically used for soft materials. It is important to control the channel length in drug delivery materials because that controls the amount of drug the patent gets. Example: Microneedle: used to make small holes in the skin to administer medication (causes no pain) Microstructures are used on implants to give structure and organization. o Photolithography Disadvantage: the material has to be a photoactive polymer - Printing o Nanoprinting: Goal is to precisely control the shape of the particle This allows you to make the material into a shape that matches other nanoparticles like viruses The shape of the particle determines where they go in the body
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