Fluid Imaging

The ability to image samples in a liquid environment vastly increases the applications of SPM technology. Imaging samples under fluid minimizes surface forces on delicate samples, allows observation of biological specimens under native conditions, and allows real-time observations of samples undergoing In order to conduct ECAFM observations with electrical potentials, an external potentiostat unit is necessary. Contact Bruker for more information.electrochemical reactions (ECAFM).

This section details basic operation of the Dimension Icon SPM in fluid, using both Contact AFM and TappingMode AFM.

Basic Principles

Attractive forces on the probe tip caused by surface tension from the adsorbed fluid layer are eliminated when samples are scanned under fluid. The reduction in tip-sample attraction allows the sample surface to be imaged with minimal force—a decided advantage when imaging biological specimens and other delicate materials. The procedure for observing samples under fluid is similar to that for observation in air; however, special hardware is required. In addition, minor adjustments must be made to correct for refractive effects as the laser beam transits air-fluid boundaries.

This section assumes familiarity with standard operation of the Dimension Icon AFM in air. If you are not familiar with operation of the AFM in air please refer to Basic Contact Mode Operation and Basic TappingMode Operation before attempting the corresponding imaging operations in fluid.

Special Hardware Requirements

• Probe Holder:

A special probe holder is required when imaging in fluid. This holder is designed to allow the laser light to reflect of the cantilever in solution while keeping the scanner tube from coming into contact with the fluid environment (see High Efficiency Direct Drive TappingMode Fluid Probe Holder for more information).

Figure 1: High Efficiency Direct Drive Fluid Probe Holder (Version 1)

Figure 2: High Efficiency Direct Drive Fluid Probe Holder (Version 2)

• Probes:

Soft cantilevers, such as DNP-S, are necessary for imaging in fluid (see Probe Selection for Fluid Techniques for more information).

• Viton Splash Shield

A Viton splash shield is provided to ensure that liquid doesn't come into contact with the scanner. This should be used in conjunction with the High Efficiency Direct Drive TappingMode Fluid Probe Holder any time fluid applications are undertaken.

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