Instruction manual

Fluid Operation
Introduction
Rev. B MultiMode SPM Instruction Manual 123
8.1 Introduction
Imaging of samples in fluid is a growing application of AFM technology. This may be prompted by
a desire to minimize surface forces on delicate samples, the need to observe biological specimens in
their natural, fluid environments, and/or the necessity to make real time observations of samples
undergoing electrochemical reactions (ECAFM). In order to conduct ECAFM observations with
electrical potentials, it is necessary to connect an external potentiostat unit. Contact Veeco for more
information.
Imaging samples under fluid eliminates attractive forces due to surface tension. This enables the
sample surface to be imaged with a minimum of cantilever tip force—a decided advantage when
imaging biological specimens and delicate materials.
Essentially, the procedure for observing samples under fluid is the same as that for Contact Mode or
TappingMode™ AFM in air; however, special hardware is utilized to contain the fluid. In addition,
minor adjustments must be made to correct for refractive effects as the laser beam transits air-fluid
boundaries.
This chapter describes Contact Mode and TappingMode AFM operation of the MultiMode SPM in
fluid, including loading the probe into the probe holder, mounting the probe holder into the head
and aligning the laser on the cantilever portion of the probe and then engaging the probe tip with the
sample.
This chapter assumes familiarity with Contact Mode and TappingMode AFM operation of the
MultiMode in air. If you are not familiar with air operation of the MultiMode, refer to the
procedures outlined in Chapter 6 and Chapter 7 before attempting to operate the AFM with a fluid
cell.
8.2 General Fluid Operation
The fluid cell consists of a small glass assembly with a wire clip for holding an AFM probe (see
Figure 8.2a). The glass surfaces provide a flat, beveled interface so that the AFM laser beam may
pass into the fluid without being distorted by an unstable fluid surface. The probe is mounted in a
rectangular groove on the bottom of the fluid cell, and held in place by a gold-coated wire clip. A
circular groove surrounds the probe and is used to seat the (optional) O-ring. Additionally, there are
two fluid ports located on the front side of the fluid cell. These ports allow for the introduction and
removal of fluid.