2006 AAPT Summer Meeting
Atomic Force Microscope
Massachusetts Institute of Technology
Biological Engineering Division
32 Vassar Street, 16-352
Bldg. 16, Room 352
Cambridge, MA 02139
shusteff ‘at’ mit ‘dot’ edu
The apparatus is a low-cost atomic force microscope (AFM) designed for use in an undergraduate teaching laboratory. An AFM measures the bending of a microfabricated cantilever beam as it interacts with sample surfaces, obtaining position and force information. The mechanical properties of our particular position sensor enable a robust and open design that makes it particularly useful in an educational context.
Construction of Apparatus:
This AFM is constructed primarily from off-the-shelf parts available from ThorLabs, Inc., Newport, New Focus, and DigiKey, with a few custom-designed machined parts. We use an interferometric position sensing scheme known as the interdigitated (ID) cantilever to obtain high resolution. These sensor probes are custom-fabricated, and can be produced using a standard process. The AFM uses a National Instruments NI-DAQ data acquisition system to interface with a PC, and is driven by software written in Matlab.
Complete design details, parts lists, and software are available online: http://web.mit.edu/be/teachAFM/
Use of Apparatus:
This AFM gives students hands-on access to nano-Newton force measurements and sub-angstrom position measurements. Its pedagogical advantage is that students interact with a complete instrument system and learn measurement principles in context. In addition to gaining an appreciation of the lower limits of position and force measurements, students learn to apply numerous concepts such as digital sampling, Fourier-domain analysis, noise sources, and error propagation. Students are able to perform a number of experiments with this AFM system, including a measurement of Boltzmann's constant, done by recording the thermal noise of the microfabricated cantilever beam, as well as measuring elastic moduli of surfaces, and imaging.