Optically trapped probes with nanometer-scale tips for femto-Newton force measurement

M R Pollard, S W Botchway, B Chichkov, E Freeman, R N J Halsall, D W K Jenkins, I Loader, A Ovsianikov, A W Parker, R Stevens, R Turchetta, A D Ward and M Towrie

We describe the development of a novel force probe, controlled by multiple optical traps, with a nanometer-scale tip that protrudes outside the direct laser radiation field. We have measured forces to an accuracy of 240 fN, which enables future experiments that probe photo-sensitive components (such as biological cells) and non-transparent objects. The probes were produced using two methods, electron beam lithography and two-photon polymerization, with the latter providing approximately twice as much trapping stiffness.

DOI