DPG Spring Meeting Poster: Video-based Axial Force Analysis for 3D Quantitative Optical Tweezers

Sebastian Knust¹, Andy Sischka¹, Andre Spiering¹, Christoph Pelargus¹, and Dario Anselmetti¹

¹: Experimental Biophysics & Applied Nanoscience, Faculty of Physics, Bielefeld University, 33615 Bielefeld, Germany


We developed and included video-based axial force analysis into our previously described optical tweezers setup [1]. By measuring the radius of a trapped microbead
we achieve an overall force resolution along the z-axis in the range of 0.2pN with a bandwidth of 120Hz, only limited by our CCD camera. With this video-based method
we overcome the remaining weak interference effects in backscattered light based force analysis when operating a microsphere in the vicinity of an interface.

We tested our setup by investigating the controlled threading and translocation of individual lambda-DNA molecules with and without attached DNA-binding ligands
through solid-state nanopores and comparing these results with previous measurements realized with photodiode intensity detection [2, 3].


[1] A. Sischka et. al., Rev. Sci. Instrum. 79, 063702 (2008)
[2] A. Sischka et. al., J. Phys.: Condens. Matter 22, 454121 (2010)
[3] A. Spiering et. al., Nano Lett. 11, 2978 (2011)


BP24.12 Poster


The setup, methods and results described in this poster are elaborated in the follow-up publication in Rev. Sci. Instrum. 83, 103704 (2012).