W. Richard Bowen and Nidal Hilal 4

34 2. MEASUREMENT OF PARTICLE ANd SURFACE INTERACTIONS
micromanipulator set-up, although where materials allow, sintering may be
used, such as with polystyrene beads. Figure 2.2 shows a typical micromanipulator
set-up, utilised in the preparation of colloid probes. This consists
of a micromanipulator platform positioned underneath an optical microscope,
and connected to an electronic control unit. Colloidal particles are
placed upside down on a cleaned microscope slide, where they adhere via
capillary forces. At one end of the slide is placed a thin smear of an appropriate
adhesive. The AFM cantilever is allowed to come into contact with
the glue, with care being taken to minimise the amount of glue present. Too
much glue may cause problems with contamination. Any excess can be
wiped off by scraping the cantilever carefully on a clean area of the slide.
The stage is then moved until a suitable particle is located. The cantilever
plus glue is then allowed to come into contact with the particle, removing it
from the surface of the slide. The glue is allowed to set and the probe is then
ready for use. An alternative method also used is to place a drop of glue on
the end of the cantilever using a fine wire. Another wire is then used to pick
up a particle using capillary adhesion and then place it on the glued end of
the lever [4].
C
A
D
FIGuRE 2.2 Illustration of a typical micromanipulator set-up. It consists of a movable
stage (A) mounted below an optical microscope (B). Inset into the top-left corner is a closeup
of the stage. Movement of the stage can be controlled via an electronic control console
(C), shown here on the left. Cantilever, particle interaction can also be monitored via a digital
video camera (D) mounted on the microscope. The AFM cantilever is introduced to the
underneath of a microscope slide mounted on the stage from the left, where it is allowed to
come into contact with glue and particles attached to the slide. Fine control of the cantilever’s
movement is attained via the manipulator joystick and vertical drive (E). On the monitor,
a V-shaped AFM cantilever is visible. The picture was taken in the laboratory of the
Department of Chemical and Environmental Engineering, University of Nottingham.
A
B
E