atomic force microscope (AFM), device that uses a spring-mounted probe to image individual atoms on the surface of a material. Unlike the scanning tunneling microscope, which is also a scanning probe microscope, the AFM can be used on materials that do not conduct electricity. In the original AFM, the probe traverses the surface, moving upward due to bumps and downward due to depressions; a laser beam reflected from the tip of the probe measures the up and down movements, and the pattern of reflected light creates an image of the surface. Another type of AFM measures the sideways deflection of the tip caused by friction as the probe moves across the surface; differences in friction can be used distinguish different atoms and molecules on the material. A third variation employs a magnetic probe; this probe does not touch the material but moves up and down in reaction to the magnetic forces between the tip and the surface. In a microchip-size AFM, the electronic circuitry and multiple probes are integrated on a sliver of silicon; although less sensitive than a full-size AFM, the device has applications in microelectronics where the multiple probes make it possible to record images very quickly.