Surface Characterization Techniques by malj


									 Surface Characterization

  –Contact Angle Analysis
  –Light Microscopy
  –X-ray Photoelectron Spectroscopy (XPS)
  –Fourier-Transform Infrared Spectroscopy (FTIR)
  –Electron Microscopy – TEM and SEM
  –Scanning Probe/Atomic Force Microscopy (SPM, AFM)
Overview of Characterization
          Penetration depths can go deeply below the
           Contact Angle Analysis
                                     Contact angle analysis provides
                                     information on the
                                     hydrophobiciyty of a material.

Contact angle is measured using
a variety of liquids on a specific
The point at which the curve
crosses 0 is the critical contact
angle, gc and used for the value
                  Light Microscopy

The Compound Microscope

                                             Above: Fluorescence can be
                                             used to make topographical
                                             features more pronounced,
                                             e.g., the ridges on the
A fibroblast. Light microscopy can be used   polymer surface.
to view surfaces as small as 0.2 um.
X-ray Techniques
Electron Spectroscopy for
Chemical Analysis (ESCA)

         Left: EXCA spectrum of
         polydimethyl siloxane (PDMS)

           Right: Spectrum for
           triflouroacetate. Binding energy
           varies with element and type of

          Left: Electrons emitted as a result of X-
          ray bombardment are separated by
          kinetic energy , and counted by the
   Attenuated Total Internal Reflectance
 Fourier Transform – Infrared Spectroscopy
FTIR passes IR radiation through a
sample, and measures the wavelengths
at which energy is absorbed. Because
molecules can vibrate by stretching,
bending and twisting and absorb
varying amounts of energy at each
frequency, FTIR provides structural and
chemical information.

                                          Above: spectrum of PDMS.
                                          Peaks include (A) C-H bond in
                                          Si-CH3 at 800 cm-1, (B) Si-O-Si
                                          bond at 1020 cm-1 and (C) C-H
                                          bond in Si-CH3 at 1260 cm-1.
Secondary Mass Ion Spectroscopy
                                     In SIMS, ion bombardment sputters off
                                     surface ions (secondary ions) that are
                                     then counted.
                                     Spectra are compared to a database to
                                     determine species, quantity, orientation

                                     SIMS components: sample and ion gun,
SIMS can damage surface, but         mass analyzer (filter), and
gives quantitative data on           processor/computer
composition as a function of depth
in a sample
Transmission Electron Microscoy –Scanning
     Electron Microscopy (TEM, SEM)

          TEM in comparison to light microscopy.
          Above right: sperm cells in light
          microscopy, below right: sperm cells in a
                                                    SEM has great depth
                                                    of focus. Left:
                                                    osteoblast cells
                                                    cultured on a
                                                    titanium mesh.

                           Right: schematic of an

Electrons can penetrate
deeply into a sample,
giving averaged chemical
information with depth .
       Scanning Probe Microscopy (SPM)
        Atomic Force Microscopy (AFM)
                                 AFM surface topography of poly (D,L-
                                 lactic acid)-poly(ethylene glycol)-
                                 monomethyl ether diblock copolymer

Right: AFM instrumentation. Stylus is
placed on sample surface. Laser
tracks movement of stylus, and
cantilever deflection is monitored.
Stage is moved up and down to
maintain contact between tip and

Above right: the greater the tip radius,
the lower the spatial resolution.

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