Biomedical Engineering Reference
In-Depth Information
Table 3.1.4-6 Scanning probe microscopy (SPM) modes
Name
Acronym
Use
Contact mode
CM-AFM
Topographic imaging of harder specimens
Tapping (intermittent force) mode
IF-AFM
Imaging softer specimens
Noncontact mode
NCM-AFM
Imaging soft structures
Force modulation (allows slope of
force-distance curve to be measured)
FM-AFM
Enhances image contrast based on surface
mechanics
Scanning surface potential microscopy
(Kelvin probe microscopy)
SSPM, KPM
Measures the spatial distribution of surface
potential
Magnetic force microscopy
MFM
Maps the surface magnetic forces
Scanning thermal microscopy
SThM
Maps the thermal conductivity
characteristics of a surface
Recognition force microscopy
RFM
Uses a biomolecule on a tip to probe for
regions of specific biorecognition on
a surface
Chemical force microscopy
CFM
A tip derivatized with a given chemistry is
scanned on a surface to spatially measure
differences of interaction strength
Lateral force microscopy
LFM
Maps frictional force on a surface
Electrochemical force microscopy
EFM
The tip is scanned under water and the
electrochemical potential between tip and
surface is spatially measured
Nearfield scanning optical microscopy
NSOM
A sharp optical fiber is scanned over
a surface allowing optical microscopy or
spectroscopy at 100-nm resolution
Electrostatic force microscopy
EFM
Surface electrostatic potentials are mapped
Scanning capacitance microscopy
SCM
Surface capacitance is mapped
Conductive atomic force microscopy
CAFM
Surface conductivity is mapped with an
AFM instrument
Nanolithographic AFM
An AFM tip etches, oxidizes, or reacts
a space permitting pattern fabrication at
10 nm or better resolution
Dip-pen nanolithography
DPN
An AFM tip, inked with a thiol or other
molecule, writes on a surface at the
nanometer scale
a material has inversion symmetry, i.e., in the bulk of the
material. At an interface, the inversion symmetry is broken
and an SFG signal is generated. Thus, SFG is exquisitely
sensitive to the plane of the interface. In practice, u
ir
is
scanned over a vibrational frequency range d where vi-
brational interactions occur with interface molecules, then
the SFG signal is resonantly enhanced and we see a vibra-
tional spectrum. The advantages are the superb surface
sensitivity, the cancellation of bulk spectral intensity (for
example, this allows measurements at a water/solid in-
terface), the richness of information from vibrational
spectra, and the ability to study molecular orientation due
to the polarization of the light. SFG is not yet a routine
method. The lasers and optical components are expensive
and require precision alignment. Also, the range in the in-
frared over which lasers can scan is limited (though it has
slowly expanded with improved equipment). However,
the power of SFG for biomaterials studies has already been
