THIS IS A MATCH constructed around information — the need for it andthe recent cost-efficient availability of it.

The AFM or MFM
In 1986, Gerd Binnig of IBM’s Zurich Research Laboratory invented the atomic force microscope (AFM), which measured the various forces between acantilever tip and features on non-conducting surfaces.

Only twenty years later, many firms that are serious about understanding and controlling surface phenomena either own an AFM (for sale on eBay for $75,000), or rent one (for $33/hr) at a university! Please see Figure 1.

Figure 1. AFM Instrument
(photo courtesy of Penn State University)

Except that they don’t use it to measure at the atomic scale. They use it to measure adhesive/repulsive forces and micron-sized topographic features.Perhaps it should be called the Molecular Force Microscope (MFM).

The MFM probe (tip) is set on a base that moves in three dimensions under vernier control of a computer (Figure 2). The tip is a thin ceramic that is mounted on the end of a cantilever beam. As the tip is either repelled by or attracted to the surface, the cantilever beam is deflected. The angle of that deflection is measured by a laser, and the force necessary to move the base is measured by a “strain cell.”

Figure 2. AFM Diagram
(courtesy of University of Toledo Department of Chemical Engineering)

The MFM produces three channels of information:

1. A plot of deflection angle vs. computer-controlled position that can be converted to a topographical map of the scanned surface.
2. The adhesive force required to separate the probe from the surface.
3. The repulsive force required to press the probe to contact the surface.

The values of both forces can be coordinated to the position informationto produce additional maps.

An MFM is a robust instrument that can be used under ambient conditions. But sample preparation is crucial and takes much more time than it does to use. Well-handled probes last at least a week. Sample time is around 2,000 seconds with around 1.5% noise:signal. Tip radius is typically 5–15 nm. The area scanned is around 100 square microns.