Biomaterials Lecture - GV. Tạ Thị Phương Hoa

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Nội dung Text: Biomaterials Lecture - GV. Tạ Thị Phương Hoa

Biomaterials Lecture Lecturer: TA THI PHUONG HOA Teaching Assistant: DINH THI NHUNG 1 Advanced Program Biomedical Engineering – HUST, Vietnam About Materials “Understanding the history of materials means understanding the history of mankind and civilization” civilization” “Who can master the materials, can master the future” future” 2 Advanced Program Biomedical Engineering – HUST, Vietnam
Part 1: Material Science & Engineering Chap. 1. Properties of materials - The structure of solids - Mechanical properties of materials - Surface properties of materials - Role of water in biomaterials Chap. 2. Classes of materials used in medicine - Polymer - Silicone - Medical fibers & biotextiles - Hydrogels - Applications of “Smart Polymers” as biomaterials - Bioresorbable and bioerodible materials 3 Advanced Program Biomedical Engineering – HUST, Vietnam Part 1: Material Science & Engineering Chap. 2.(cont.) - Natural materials - Metals - Ceramics, glasses, and glass-ceramics - Composite - Nonfouling (Anti-fouling) surfaces - Surface modification of materials used in medicine - Textured and porous materials - Surface-immobilized Biomolecules 4 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.1. Properties of materials- The structure of solids The periodic table 5 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.1. Properties of materials- The structure of solids 1.1. Structure of solids Which states of materials do you know? The differences of them? What determine the properties of material? What are solids? - Their constituent atoms are held together by strong interatomic forces - Structure, physical properties: depend on the nature and strength of the interatomic bonds - Strong bonds: ionic, covalent and metallic Structure of solids: on many levels of scale - Atomic or molecular: 0.1- 1 nm - Nanoscale or ultrastructural: 1 nm- 1 µm - Microstructural: 1 µm- 1 mm - Macrostructural: > 1mm 6 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.1. Properties of materials- The structure of solids Atomic bonding: primary interatomic bonds and secondary bonds Primary interatomic bonds (strong bonds) Ionic bonding: * Formed by exchanging electrons between metallic and nonmetallic atoms - Electron donor atoms (metallic) transfer one or more electron to an electron acceptor (nonmetallic) to form cation and anion - Cations and anions strongly attract each other by Coulomb effect - The attraction of cations and anions constitutes IB (Hummel, 1997) • Ionic solid structures are limited in their atomic arrangement • Bonding energy: relative large, between 600- 1500 kJ/mol (3-8 eV/atom), leads to relative high melting temperature • Poor electrical conductor, relative low chemical reactivity • Examples: NaCl, MgO 7 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.1. Properties of materials- The structure of solids Loosely bound electrons are tightly held in the locality of the ionic bonding Fig. 1. Schematic representation of ionic bonding in sodium chloride (NaCl) 8 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.1. Properties of materials- The structure of solids Covalent bonding: - Elements between metals and nonmetals (equal tendency to donate and accept electrons), many nonmetals, molecule containing dissimilar atoms - Bonding by sharing valence electron to form stable electron structure (all valence electrons in pair localized at valence bonding) - Bonding is highly directional and strong, may be very strong (diamond), • Materials as poor electric conductors • Examples: H2, Cl2; Si, C; CH4, H2O 9 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.1. Properties of materials- The structure of solids Fig. 2: Schematic representation of covalent bonding in a molecule of methane (CH4) 10 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.1. Properties of materials- The structure of solids Metallic bonding: - Three-dimensional pattern with valence electrons migrating within atoms (Fig.3) - Bonding may be week or strong, energies range from 68kJ/mol (0.7 eV/atom) for mercury to 850 kJ/mol (8.8 eV/atom) for tungsten - Material may be very strong (cobalt) and have very high melting point - Good electrical and thermal conductor 11 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.1. Properties of materials- The structure of solids Valence electrons can move freely within atoms (sea of valence electrons) Fig. 3. Schematic illutration of metallic bonding 12 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.1. Properties of materials- The structure of solids Secondary bonds (week bonds) Van der Waals (physical bonds) Fig.4. Van der Waals bonding between two dipoles - Forces arise when electrons are not distributed equally among ions that can form dipoles - Much weaker than hydrogen bonds, effect is over a short distance 13 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.1. Properties of materials- The structure of solids Hydrogen bonds - Hydrogen bonds can arise when the hydrogen atom is covalently bonded to an electronegative atom so that it becomes a positive ion - The electrostatic force between them can be substancial - Bonding mechanisms are now discussed briefly Fig.5. Hydrogen bonding in hydrogen fluoride (HF) 14 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.1. Properties of materials- The structure of solids Atomic structure • Crystal - A solid whose atoms and ions are arranged in an orderly repeating pattern in three dimensions - Atoms can be very closely packed - Number of primary bond is maximized - Energy of aggregate is minimized • Crystal structure - Unit cell have all the geometric properties of whole crystal 15 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.1. Properties of materials- The structure of solids Materials, their chemical bonds and atom structure Table 1: Strength of different chemical bonds as reflected in their heat of vaporization 16 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.1. Properties of materials- The structure of solids Fig. 6. Some materials exhibit nearly ideal covalent, metallic or ionic bonding, but most materials exhibit a hybrid bond types 17 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.1. Properties of materials- The structure of solids * Metals A: Face-centered cubic (FCC) B: Full size atom C: Hexagonal close-packed (HCP) D: Body-centered cubic (BCC) Fig.7. Typical metal crystal structure (unit cells) 18 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.1. Properties of materials- The structure of solids * Crystal structure of carbon Tab. 2: Related physical properties of diamond and graphite 19 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.1. Properties of materials- The structure of solids cubic hexagonal Fig.8: Crystal structure of carbon; A: diamond, B: graphite 20 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.1. Properties of materials- The structure of solids • Ceramics - Various combinations of ionic and covalent bonding - Tightly packed structure - Carbon: often included with ceramics • Polymer - Thermoplastics - Thermoset: three dimensions 21 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.1. Properties of materials- Mechanical properties Mechanical properties of materials Properties of solids? Important properties for biomaterials: mechanical and chemical Stress- Stress- Strain behavior For materials that undergo a mechanical deformation: - Normalized load: Stress = Force/cross-section area (N/m2) - Normalized deformation: Strain = Change in length/Original length - Tension & compression (load is perpendicular to loading direction) - Shear (load is parallel to the area supporting it & dimension change is perpendicular to the reference dimension 22 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.1. Properties of materials- Mechanical properties Tensile stress & tensile strain Shear stress and shear strain 23 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.1. Properties of materials- Mechanical properties Elastic behavior - In tensile test - Extension: proportional to the load (Hook law-1687) 24 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.1. Properties of materials- Mechanical properties Elastic constants  = E ε , tension and compression -E & G: proportionality constants =G, shear - Tensile constant E: tensile modulus (Young’s modulus) - G: shear modulus - E and G represent inherent properties of materials - Strong bonds: high moduli, small strain - Week bonds: low moduli 25 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.1. Properties of materials- Mechanical properties Stress versus strain for elastic solids 26 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.1. Properties of materials- Mechanical properties Tab.3. Mechanical properties of some important implant materials and tissues 27 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.1. Properties of materials- Mechanical properties Isotropy Isotropy: properties are same in all direction E & G: needed to fully characterize the stiffness of an isotropic material Single crystal: anisotropic Polycrystalline materials: on average isotropic 28 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.1. Properties of materials- Mechanical properties Mechanical testing 29 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.1. Properties of materials- The structure of solids Mechanical properties derivable from a tensile test 30 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.1. Properties of materials- Mechanical properties Plastic deformation -Only metals exhibit true plastic deformation -Ceramic and many polymer do not undergo -Important for shaping metals and alloys Stress versus strain for a ductile material 31 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.1. Properties of materials- Mechanical properties Creep and viscous flow A: Elongation vs time at constant load (creep) B: Load vs time at constant elongation A: Dash pot or cyclinder and piston model of viscous flow B: Dash pot and spring model 32 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.1. Properties of materials- Mechanical properties Toughness -The ability of a material to plastically deform under the influence of the complex stress field at the tip of a crack - Brittle fracture (glass, ceramics, graphite, very hard alloys, some polymer like PMMA-bone cement - Elastic fracture - Fracture toughness test: . Single Edge Notched Bend (SENB) Test, ISO 13586: 2000 (E), . GIC & KIC: Fracture toughness . KIC: Critical Stress Intensity Factor; I (mode I): loading is applied perdendicular to the crack path KIC= (EGIC)1/2 Sample: L = 78 mm, w = 16mm; B = 4mm, a = 8mm 33 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.1. Properties of materials- Mechanical properties Fatigue - Is process by which structure fail as a result of cyclic stresses (usually less than ultimate tensile stress) - Important for dynamic loaded structure - Fatigue strength is sensitive to environment, temperature, corrosion, deterioration and cyclic rate 34 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.1. Properties of materials- Mechanical properties A: Stress versus time in a fatigue test B: Fatigue stress versus cycles to failure 35 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.1. Properties of materials- Surface properties Surface properties of materials •Surface properties are very important for biomaterials •Surface: boundary between different phases 36 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.1. Properties of materials- Surface properties Surface tension * Surface energy dG = dw - dA w: work done on the surface area change dA : surface energy of the material • Contact angle • Surface structure (surface area and surface chemistry decide surface energy) • Surface energy: very important for wettability and adhesion (adsortion & chemisorbtion) Surface tension of some materials Substances Temperature, oC Surface tension, N/m Mercury 20 0.465 Lead 327 0.452 Zinc 419 0.758 Copper 1131 1.103 Gold 1120 1.128 37 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.1. Properties of materials- Surface properties Several methods to determine the contact angle of solid and liquid Sessile drop method with goniometer Wilhelmy plate method with Tensiometer Micro balance F (µN) Wilhelmy equation γsv F Drop on flat substrate vapour θ contact cos  angle p lv γlv γsl liquid Drop on fibre 38 Advanced Program Biomedical Engineering – HUST, Vietnam
Chap.1. Properties of materials- Surface properties - Roughness is a very important factor for surface energy (due to surface area) A: Rough, step, smooth; B: composed of different chemistries;C: inhomogeneous in plane D: inhomogeneous in with depth; E: highly crystalline or disordered; F:Crystalline surface with many organisations 39 Advanced Program Biomedical Engineering – HUST, Vietnam Chap.1. Properties of materials- Surface properties - Surface chemistry is also very important for surface tension (due to chemical composition, especially functional groups at the surface) - Hydrophilic groups - Hydrophobic groups Evaluation of a surface: -Measurement of contact angle (general surface energy) -Study morphology of the surface: SEM… -Study surface roughness: AFM, SEM -Study the surface chemistry: IR (FTIR), XPS, Raman Spectroscopy, SIMS 40 Advanced Program Biomedical Engineering – HUST, Vietnam