AFM stability of 5 pm/min at room temp

Atomic force microscopy (AFM) is finding more use in biological applications, and this usually means making measurements in liquids. However, the very reason AFM is useful -- its nanometer-scale sensitivity -- also makes the AFM probe very sensitive to environmental factors such as acoustic noise, temperature shifts and vibration. Thus, it becomes a challenge to keep the AFM probe exactly in one place (to measure protein interactions, for example) or to repeatedly return to a precise position.  

Extremely cold temperatures and a ultra-high vacuum can help overcome stability challenges, but aren't friendly to biological samples nor are they easy to set up. 

Researchers from the National Institute of Standards and Technology (NIST) and the University of Colorado have turned to using two additional laser beams (shown as red and green in the image) to sense the 3-D motion of the specimen and AFM probe. One beam lets them sense lateral and vertical drift in the sample using a reference point while the second beam lets them detect unwanted movement of the probe tip. The AFM measurements can be corrected using this information.

The researchers have previously reported on this technique, but in a new Nano Letters paper they used it to achieve a 100-fold improvement in AFM stability at room temperature. They controlled an AFM probe’s 3-D position to better than 40 pm over 100 s, and reported a long-term drift of only 5 pm/min. when imaging at room temperature.

In addition to biological applications, the technique would be useful for nanoscale manufacturing, which requires precise repeated AFM movements and measurements. 

What challenges have you faced with AFM stability?

Image: Copyright G.Kuebler/JILA/CU.

Sources: G.M. King, A.R. Carter, A.B. Churnside, L.S. Eberle and T.T. Perkins. Ultrastable atomic force microscopy: Atomic-scale stability and registration in ambient conditions. Nano Letters, Article ASAP, March 12, 2009 (DOI: 10.1021/nl803298q).

NIST Press release