BIOM 101 CH. 15 notes
BIOM 101 CH. 15 notes BIOM 101
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This 3 page Class Notes was uploaded by firstname.lastname@example.org Notetaker on Thursday October 1, 2015. The Class Notes belongs to BIOM 101 at Colorado State University taught by Dr. James, Dr. Popat in Fall 2015. Since its upload, it has received 13 views. For similar materials see Introduction to Biomedical Engineering in Engineering and Tech at Colorado State University.
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Date Created: 10/01/15
"biomaterial" : a nonviable material used in a medical device, intended to interact with biological systems o Not living materials o Should be biotolerable (non-harmful) o "any synthetic or natural material used in medicine in contact with living systems AND all natural materials (living or not) "biocompatible" : the ability of a material to perform with an appropriate host response in a specific application Artificial organ: replacing the function and sometimes structure of body tissues and organs o Membrane oxygenator o Hemodialysis (replace kidney function) o Total joint replacement o Skin grafting Biohybrid: synthetic components are used to support the activity of living components o Partially tissue engineered o Combinations of synthetic and natural materials o Bio-inspired or bio-mimetic Biomaterial properties o Biomaterials may be characterized by the following properties Surface Surface properties that impact cell- material interactions Non- specific interactions (electrostatic forces, van der walls, …) Specific interactions (cell surface receptor binding) Protein adsorption (cells attaching to proteins) Bulk Atomic/ molecular structure -> microstructure -> properties Mechanical Biological Thermal, electrical, magnetic, optical … o Length scales of material properties Subcellular (<10 um) Cellular (10-100 um) Subpracellular (>100 um) Classes of materials o Metals o Ceramics o Polymers o Composites Material microstructure o Amorphous Crystalline Metals "glassy metals" Structural metals Ceramics Glass Engineering ceramics Polymers Semi- crystalline; amorphous & domains molecules too big for crystalline 100% crystallinity Composites Characteristics based upon Materials constituent Mechanics and materials o Forces Displacement Translations and rotations Stresses Material properties Deformation (strain) Types of stresses o Tension o Compression o Shear o Torsion Mechanical properties (look on canvas for graphs) o Metal o Thermoplastic material above Tg o Elastomer o Ceramics, glasses, and concrete E= elastic modulus O= E Lay terminology and tradeoffs o Stiffness E*I, E=modulus, material property only o Strength As strength and modules goes up, ductility goes down o Brittle Low e i o Ductile High ei o Hardness As hardness goes up, toughness goes down Polymers o Majority of synthetic biomaterials are polymeric o MACROmolecule Hundreds of thousands of atoms per molecule o Viscoelastic= Elastic + Viscous Changes with temperature o Thermosets vs thermoplastics Presence/absence of crosslinks (covalent bonds between chains) o Phase transitions T m 1st order phase transition (liquid to solid) T g Not a 1st order phase transition; related to changes in intermolecular bonding o Synthetic vs Natural Polymers Synthetic Polyethylene (PE) Polyvinylchloride (PVC) PMMA (plexiglas), PC (Lexan), PS, PTFE (Teﬂon) . . . . Durable, consistent Simple microstructures NOT living Easy to mass produce Natural wood, rubber, silk, wool, cotton, wood still the most common construction material in the world! Proteins, polysaccharides, collagen, tendon/ligament, cartilage (really ECM), bone, toucan beaks, mother of pearl, insect cuticle Hierarchical, multi-functional Not easy to mass produce LIVING and SELF HEALING o Clotting o Intrinsic: activated by the presence of charged surfaces Requires factors VIII, IX, X, XI, XII o Extrinsic: the formation of a clot in response to tissue injury and vessel damage Initiated by tissue factor and activated factor VII Hemodialysis o The ideal dialysis membrane should provide: Selective separation Efficient removal of waste molecules Low resistance to blood flow Compatible materials that exhibit low toxicity and low susceptibility to clotting Ease of use Low cost and reproducible operation o The total surface area of the fibers available for exchange of molecules is given by: S= N(pi)dL N is the number of hollow fibers in the unit D is the diameter of each fiber L is the length of each fiber Dialysance (D) represents the overall performance of a dialysis unit in removing a particular solute from the blood under the units current state of operation o expressed in units of flow rate (mL/min) Clearance (CL) is an extension of a concept used frequently to describe behavior of the kidneys and is commonly used to describe the overall performance of artificial kidneys o Volume of blood per unit time in which all of a solute is removed The extraction ratio E is the solute concentration change in the blood compared to the theoretical solute concentration change that would occur if the blood and dialysate came to equilibrium
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