His finding will force 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 will be published in the April issue of Review of Scientific Instruments.
In atomic force microscopy, small cantilevers are used to profile surface topography and structure. Shortly after the invention of the Atomic Force Microscope (AFM), almost two decades ago, V-shaped cantilevers were introduced to minimise the effect of lateral forces on image quality, a problem faced by the original rectangular design. 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 im
Contact: Jason Major
University of Melbourne