W. Richard Bowen and Nidal Hilal 4

ABBREvIATIONs ANd syMBOLs 23
electron microscope (SEM) image shows a 5-μm diameter silica bead
attached with glue close to the apex of a standard AFM microcantilever.
The first reported use of an AFM with a colloidal probe was by Ducker
et al. [116, 117] who attached a 3.5-μm silica sphere to an AFM cantilever
and used it to measure forces between the sphere and a silica surface as
a function of electrolyte concentration and pH. Since then this technique
has been used to probe the interaction forces between various materials
and surfaces including silicates and other inorganic materials [80, 83, 117,
118], protein- and polymer-coated beads and surfaces [119–122], membrane-fouling
materials and membranes [123], biological cells and surfaces
[124, 125]; between drug particles which are important in powder
formulations [81, 84, 87]; and for probing the rheological properties of
liquids [110, 126]. See Chapter 2 for more detail on the preparation of colloid
probes.
abbrevIaTIons and symbols
AFM Atomic force microscopy/microscope
b Outer width of the base of V-shaped cantilever m
E Young’s modulus N m�2 F Force normal to sample surface N
Flat Lateral forces N
JKR Johnson, Kendall and Roberts theory
k Spring constant of cantilever N m�1 kB Boltzmann’s constant (1.38 � 10�23 ) J K�1 kc Corrected k N m�1 klat Lateral spring constant N m�1 km Uncorrected k N m�1 kref Reference cantilever spring constant N m�1 k � Torsional spring constant N m �1
l Cantilever length m
M Mass added to cantilever kg
P Positional noise power of fundamental resonant peak
PDMS Polydimethylsiloxane
Q Quality factor of cantilever –
SPM Scanning probe microscopy
STM Scanning tunnelling microscopy/microscope
t Cantilever thickness m