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Lecture 22: Chapter 4: Surface Characterization in Biomaterials and Tissue Engineering

Lecture 22: Chapter 4: Surface Characterization in Biomaterials and Tissue Engineering. Really just a bunch of Microscopy. It’s from the Greek, mikros (small) and skopeo (look at). Objectives.

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Lecture 22: Chapter 4: Surface Characterization in Biomaterials and Tissue Engineering

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  1. Lecture 22: Chapter 4: Surface Characterization in Biomaterials and Tissue Engineering Really just a bunch of Microscopy. EEBE 512/ENEL 619.15 Dr. KE Jones

  2. It’s from the Greek, mikros (small) and skopeo (look at). EEBE 512/ENEL 619.15 Dr. KE Jones

  3. Objectives • Starting from the de Broglie equation, demonstrate that TEM resolution depends on the voltage of the accelerating field • Describe the principle and sample preparation for: • TEM, SEM, 2 modes of STM & SFM, XPS, AES, SIMS, ISS, FT-IR, ATR, FTIR-ATR EEBE 512/ENEL 619.15 Dr. KE Jones

  4. Outline EEBE 512/ENEL 619.15 Dr. KE Jones

  5. Why EM? • The topography of biomaterials we are interested in are very small. • ceramics • composites • metals • polymers EEBE 512/ENEL 619.15 Dr. KE Jones

  6. EEBE 512/ENEL 619.15 Dr. KE Jones

  7. Why electrons? It all started with light, but even with better lenses, oil immersion and short wavelengths, resolution was only about 0.2 mm/1000x = 0.2 micrometers. 1920's EEBE 512/ENEL 619.15 Dr. KE Jones

  8. EEBE 512/ENEL 619.15 Dr. KE Jones

  9. de Broglie equation EEBE 512/ENEL 619.15 Dr. KE Jones

  10. TEM invented in 1931 Dr. Ernst Ruska at the University of Berlin. Physics, 1986 EEBE 512/ENEL 619.15 Dr. KE Jones

  11. Fig 4.4 (a) TEM • e- can “scatter” or pass thru sample (i.e. slide projector) • transmitted e- (no scat) produce image • The denser parts of the sample scatter more e- > less e- transmitted > appears darker Principles EEBE 512/ENEL 619.15 Dr. KE Jones

  12. TEM cont’ Chemical (fixation, washing, dehydration, infiltration with solvents & resins, embedding and curing) Ultamicrotomy: 30 - 60 nm Stained with e- dense material Sample Prep EEBE 512/ENEL 619.15 Dr. KE Jones

  13. TEM (the end) • Only unscattered e- are visualized. • No 3D, can’t see surface (although shadowing) • Can’t cut everything small enough. EEBE 512/ENEL 619.15 Dr. KE Jones

  14. Carbon Nanotubes as Nanoscale Mass ConveyorsAtom Transport at the Nanoscale Four images, each taken at 60 second intervals, portray the rightward march of indium atoms along a carbon nantoube under an applied bias of 2 volts. The ends of the nanotube, where the electrical contacts are made, are out of view to the left and right. Reversing the direction of the voltage reverses the direction of motion. Model depiction of the motion of atoms along a single-walled carbon nanotube. In principle, this phenomenon could be the basis for arrays of nano-sized conveyor belts delivering mass to specific locations atom-by-atom or picking up material at one site and delivering it to another. Image created by K. Jensen. 100 nm Materials Sciences Division—Lawrence Berkeley National Laboratory A. Zettl , 04-5

  15. Scanning Electron Microscope First true SEM, 1942, resolution 50 nm, magnification 8000x. Now, 1 nm & 400 000x. EEBE 512/ENEL 619.15 Dr. KE Jones

  16. Fig. 4.4 (b) SEM • uses e- that interact with sample • detector • production of 2ndary e- > detector > more 2ndary e- in dense areas • 3D-image of surface features Principles EEBE 512/ENEL 619.15 Dr. KE Jones

  17. SEM cont’ Dry and stable in vacuum Apply a thin metal coating to specimen to make it conductive Bunch of other stuff not mentioned in text. Sample Prep EEBE 512/ENEL 619.15 Dr. KE Jones

  18. UofA Electron Microscope Facility http://www.ualberta.ca/~mingchen/index.htm EEBE 512/ENEL 619.15 Dr. KE Jones

  19. Butterfly wing surface EEBE 512/ENEL 619.15 Dr. KE Jones

  20. EEBE 512/ENEL 619.15 Dr. KE Jones

  21. Origami crane folded by Dr. Ming Chen EEBE 512/ENEL 619.15 Dr. KE Jones

  22. Where are we… EEBE 512/ENEL 619.15 Dr. KE Jones

  23. Scanning Tunneling Microscope • uses e- tunneling effect • apply voltage between probe tip and sample surface • tunneling current develops • measures mech &/or elec properties at atomic level • images from voltage, current and/or probe position Principles EEBE 512/ENEL 619.15 Dr. KE Jones

  24. STM cont’ Two Modes • Constant current: • bumpy surface • feedback through high gain voltage amps, keeps tunneling current constant by moving probe • voltage & 3d position • Constant height: • flat surface • current & 2d position EEBE 512/ENEL 619.15 Dr. KE Jones

  25. Scanning Force Microscope • also Atomic Force Microscope (AFM) • measures atomic forces between probe and sample surface • van der Waals (attactive, dominate @ large dist) • exclusion principle (repulsive, dominate @ near dist) • piezoelectric element controls movement Principles EEBE 512/ENEL 619.15 Dr. KE Jones

  26. STM cont’ Two Modes • Constant force: • feedback of force controls piezoscanner that controls sample position • piezoscanner position • Constant height: • sample at constant height • measure deflection of cantilever (optical) • contact or not (shear force problem) EEBE 512/ENEL 619.15 Dr. KE Jones

  27. STM cont’ Fig 4.9 Optical lever EEBE 512/ENEL 619.15 Dr. KE Jones

  28. Objectives • Starting from the de Broglie equation, demonstrate that TEM resolution depends on the voltage of the accelerating field • Describe the principle and sample preparation for: • TEM, SEM, 2 modes of STM & SFM, XPS, AES, SIMS, ISS, FT-IR, ATR, FTIR-ATR EEBE 512/ENEL 619.15 Dr. KE Jones

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