November 14, 2005EEBE 512/ENEL Dr. KE Jones Lecture 22: Chapter 4: Surface Characterization in Biomaterials and Tissue Engineering Really just a bunch of Microscopy.

EEBE 512/ENEL Dr. KE Jones November 14, 2005 It’s from the Greek, mikros (small) and skopeo (look at).

EEBE 512/ENEL Dr. KE Jones November 14, 2005 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 Dr. KE Jones November 14, 2005 Outline

EEBE 512/ENEL Dr. KE Jones November 14, 2005 Why EM? The topography of biomaterials we are interested in are very small. ceramics composites metals polymers

EEBE 512/ENEL Dr. KE Jones November 14, 2005

EEBE 512/ENEL Dr. KE Jones November 14, 2005 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.

EEBE 512/ENEL Dr. KE Jones November 14, 2005

EEBE 512/ENEL Dr. KE Jones November 14, 2005 de Broglie equation

EEBE 512/ENEL Dr. KE Jones November 14, 2005 TEM invented in 1931 Dr. Ernst Ruska at the University of Berlin. Physics, 1986

EEBE 512/ENEL Dr. KE Jones November 14, 2005 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

EEBE 512/ENEL Dr. KE Jones November 14, 2005 TEM cont’ 1.Chemical (fixation, washing, dehydration, infiltration with solvents & resins, embedding and curing) 2.Ultamicrotomy: nm 3.Stained with e- dense material

EEBE 512/ENEL Dr. KE Jones November 14, 2005 TEM (the end) Only unscattered e- are visualized. No 3D, can’t see surface (although shadowing) Can’t cut everything small enough.

Materials Sciences Division—Lawrence Berkeley National Laboratory 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. Carbon Nanotubes as Nanoscale Mass Conveyors Atom Transport at the Nanoscale A. Zettl, nm 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.

EEBE 512/ENEL Dr. KE Jones November 14, 2005 Scanning Electron Microscope First true SEM, 1942, resolution 50 nm, magnification 8000x. Now, 1 nm & x.

EEBE 512/ENEL Dr. KE Jones November 14, 2005 Fig. 4.4 (b) SEM interact uses e- that interact with sample detector production of 2ndary e- > detector > more 2ndary e- in dense areas 3D-image of surface features

EEBE 512/ENEL Dr. KE Jones November 14, 2005 SEM cont’ 1.Dry and stable in vacuum 2.Apply a thin metal coating to specimen to make it conductive 3.Bunch of other stuff not mentioned in text.

EEBE 512/ENEL Dr. KE Jones November 14, 2005 UofA Electron Microscope Facility ~mingchen/index.htm

EEBE 512/ENEL Dr. KE Jones November 14, 2005 Butterfly wing surface

EEBE 512/ENEL Dr. KE Jones November 14, 2005

EEBE 512/ENEL Dr. KE Jones November 14, 2005 Origami crane folded by Dr. Ming Chen

EEBE 512/ENEL Dr. KE Jones November 14, 2005 Where are we…

EEBE 512/ENEL Dr. KE Jones November 14, 2005 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

EEBE 512/ENEL Dr. KE Jones November 14, 2005 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 Dr. KE Jones November 14, 2005 Scanning Force Microscope also Atomic Force Microscope (AFM) measures atomic forces between probe and sample surface van der Waals (attactive, large dist) exclusion principle (repulsive, near dist) piezoelectric element controls movement

EEBE 512/ENEL Dr. KE Jones November 14, 2005 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 Dr. KE Jones November 14, 2005 STM cont’ Fig 4.9 Optical lever

EEBE 512/ENEL Dr. KE Jones November 14, 2005 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