Since its invention in 1986, the Atomic Force Microscope (AFM) has revolutionized the way scientists quantitatively observe and think about the chemical, biological and physical world.
In atomic force microscopy, very small cantilevers are placed in light contact with a sample and moved across its surface, detecting any change in surface topography at a size level of the sample’s individual atoms. Cantilever calibration is a fundamental issue in the use of the instrument. Shortly after the invention of the AFM, V-shaped cantilevers were introduced to minimise the effect of lateral forces on image quality to correct problems faced by the original rectangular design. Now, throwing 15 years of accepted scientific practice out the window, an Australian mathematician has discovered a design flaw in the key cantilever component of AFMs, forcing a rethink into the design and use of an instrument that has become a cornerstone of scientific measurement and analysis. Dr John Sader, at University of Melbourne’s Department of Mathematics and Statistics, and Particulate Fluids Processing Centre, used established mechanical principles to prove that the popular V-shaped cantilever inadvertently degrades the performance of the instrument and delivers none of its intended benefits. Sader’s research reveals that this attempt to rectify the lateral force problem was based on a false assumption. Instead of increasing the resistance to twisting, V-shaped microcantilevers actually maximise twist and degrade the performance of the instrument. “This finding is surprising and counterintuitive, contradicting accepted practice and manufacturing standards worldwide where the V-shaped cantilever is the standard due to its alleged advantages,” says Sader. Users of the atomic force microscope have long put up with the geometric complexity of the V-shaped microcantilever, with resulting difficulties in calibration and interpretation, to gain improved lateral performance. Sader’s calculations establish that the simple cantilever design of a straight beam proposed for the original atomic force microscope (Physical Review Letters, 1986) offers greatly improved performance over the V-shape while facilitating calibration and measurement interpretation. This finding has the potential to revolutionise the industry by setting a single universal standard and improving the performance of the instrument, while greatly simplifying its operation. “Although the V-shape certainly offers strength and stability in the construction industry, its misuse has had a detrimental effect in the field of nano-science,” says Sader. His research will be published in the April issue of Review of Scientific Instruments.
Think the field of atomic force microscopy and looking at individual atoms is really exotic and somehow beyond you, your means and your capabilities? Ha ha ha. Sure, they handed out a Nobel Prize for the first one built in 1986, but here’s instructions for building your own AFM today.