Scanning Probe Microscopy (SPM) comprises many techniques reflecting interaction of a tip with investigated surface and providing information about the surface’s topography, magnetic, electric and elastic properties The Scanning Tunneling Microscopy (STM) and Atomic Force Microscopy (AFM) were the first invented scanning microscopes.
    The basic principle of STM is that the tunneling current between a conductive tip and a sample is exponentially dependent on their distance. As the tip scans the sample’s surface, it encounters sample features of different heights, resulting in an exponential change in the tunneling current. A feedback loop is used to maintain a constant tunneling current during scanning by vertically moving the scanner at each (x,y) data point until a “setpoint” current is reached. This technique is typically limited to conductive and semiconducting surfaces.
   In case of soft biological materials and polymers Atomic Force Microscopy (AFM) turned out to be more appropriate. During scanning the tip experiences interactions originating from ionic repulsion, van der Waals, capillary, electrostatic and magnetic forces, or elastic and plastic deformations.
There are 3 primary modes of AFM:

• Contact Mode (The main interacting forces between the tip and the surface are very short range repulsive forces)
• Tapping Mode (Cantilever oscillates over the sample’s surface at a frequency close to its resonance frequency)
• Non-Contact Mode (For nondestructive analysis, but with worse resolution)

     AFM can provide information about following surface properties: friction and adhesion forces, viscoelastic properties, Young modulus (Lateral Force Microscopy , Force Modulation Microscopy, Phase Detection Microscopy), magnetic structure (MFM), electrostatic properties (EFM), electric properties: current distribution (Conductive AFM),  carrier density or dopant concentration (ang. SCM).
Any kind of samples can be analyzed: polymers, adsorbed molecules, films, fibres, powders, in air, in controlled atmosphere or in liquid medium.
Application:

1. metals: tooling studies, roughness measurements, corrosion studies...
2. solid powder catalysts: aggregate structural determination,
3. polymers: determination of morphology and surface properties, kinetic studies, aging phenomena, surface treatment modifications, adhesion force measurement and indentation,
4. biological samples, biomaterials: macromolecules association and conformation studies, adsorption, kinetic of molecules on polymer surfaces, nano- and microparticle structures, Langmuir-Blodgett, film studies.

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