Working model of an atomic force microscope

To explain the principles of an atomic force microscope (AFM) at the level of introductory physics, we have created an inexpensive model of an AFM using a modified phonograph stylus in place of the AFM cantilever and tip. The sample is positioned under the stylus using a micrometer stage. A 10 mW laser diode is used to produce a beam, which reflects off a very small mirror glued to the end of the stylus. No electronic detection is used, and students measure the deflection of the tip directly from the movement of the laser beam on graph paper. The laser beam is deflected roughly 1 cm for each 10 μm of stylus deflection, making it easy to collect data.