Lateral Force Microscopy (LFM) is a scanning probe microscopy (SPM) technique that identifies and maps relative differences in surface frictional characteristics. It is one of several techniques developed as extensions to the basic topographical mapping capabilities of SPM. LFM is particularly useful for differentiating among materials on surfaces. Applications include identifying transitions between different components in polymer blends, composites and other mixtures, identifying organic and other contaminants on surfaces, delineating coverage by coatings and other surface layers, and chemical force microscopy using functionalized tips. In standard contact mode atomic force microscopy (AFM), the probe is scanned over the surface (or the sample is scanned under the probe) in an x-y raster pattern. A laser focused on the cantilever (the substrate which supports the probe tip) is reflected onto a segmented photodiode detector to monitor the deflection of the cantilever due to surface topography. A feedback loop maintains a constant force on the sample by adjusting the height of the cantilever to compensate for topographical features. The result is a three-dimensional map of the sample surface.

With the lateral force technique, the probe is scanned perpendicular to its length; i.e. sideways on the fast axis and forward back on the slow axis. The torsion, or twisting, of the cantilever supporting the probe will increase or decrease depending on the frictional characteristics of the surface (greater torsion results from increased friction). Since the laser detector has four quadrants, it can simultaneously measure and record topographic data and lateral force data. Both of these data sets can be viewed as side-by-side images in real time, as well as stored and processed independently.