Repulsive Casimir forces
DOI: 10.1063/PT.3.4711
The article “Science and technology of the Casimir effect ” by Alex Stange, David Campbell, and David Bishop (Physics Today, January 2021, page 42) presents data from a 2009 experiment by Jeremy Munday and coworkers 1 that shows that Casimir forces can be repulsive. Sixteen years earlier we published similar results. 2
As Stange and coauthors point out, the Casimir force is emerging as a technological tool to manipulate matter at small scales. Our earlier effort to create repulsive and nearly neutral Casimir and van der Waals interactions was motivated by an attempt to improve the imaging resolution of contact-mode atomic force microscopy (AFM). The idea was to eliminate the jump-to-contact instability associated with attractive Casimir interactions, which elastically deforms the AFM tip, sets a lower limit on its effective size, and reduces imaging resolution. Imaging with special fluids works to eliminate that instability, but the fluids we had to use, bromo- and methylnaphthalene, were not compatible with biological materials. Since our hope was to image molecules such as DNA, we did not pursue further the manipulation of Casimir forces.
References
1. J. N. Munday, F. Capasso, V. A. Parsegian, Nature 457, 170 (2009). https://doi.org/10.1038/nature07610
2. J. L. Hutter, J. Bechhoefer, J. Appl. Phys. 73, 4123 (1993). https://doi.org/10.1063/1.352845
More about the authors
John Bechhoefer, (johnb@sfu.ca) Simon Fraser University, Burnaby, British Columbia, Canada.
Jeffrey L. Hutter, (jhutter@uwo.ca) University of Western Ontario, London, Ontario, Canada.
