An atomic force microscope (AFM) can be used to measure small height differences in indentations or surfaces. Through the use of various control schemes and electrical actuation, this microscope can automatically determine features of a surface, such as surface gradients. My role in this project was integrating and testing an atomic force microscope.

Central to the atomic force microscope was a cantilever beam/probe. When vibrated and touched to a surface, one can measure the resulting frequency differences to estimate height. For this experiment, we controlled the Y axis (left and right) of a moving platform using a stepper motor attached to a lead screw. For the X axis (forward and backwards), A voice coil actuator was used. All actuator inputs as well as delta frequencies were interpreted through the use of a myRIO from National Instruments. The tip of the AFM probe would be gently dragged across the entire area of a surface while vibrating in order to completely measure height over an area. A coin was utilized in order to have a very gentle topography to map. Vibration frequencies were tracked via the use of a Hall effect sensor.

The experimental AFM setup was successful. A bitmap recreation of topography values resulted in a near identical image to the original coin that was mapped. This was the case for a variety of other coins tested in this experimental setup. Some topography values varied depending on the approach of the probe on top of the coin from a certain direction. Dropping off a ridge would result in a temporary over estimation of depth.

The AFM probe setup could be improved in a variety of ways. Most importantly, an adjustable Z axis (up and down) could result in more objects of varying thickness being tested. The precision, resolution, and accuracy of the measurements were excellent for the amount of resources available for producing the setup. Time considerations caused the probe to move faster in the X and Y axis than what was desirable. Increasing the scan time could result in further more accurate representations of topography surfaces.