Design and realization of a high-stability optical tweezer

We present a method in which we stabilize mechanically an optical tweezer setup over a period ranging up to 30 min. A feedback loop is used to correct the mechanical and thermal drifts. The position of a fixed object on the sample surface is measured with a CCD device and its fluctuations analyzed and used to maintain its position fixed with three piezoelectric devices. With this setup, we obtain a spatial stability of 1.5 nm in the radial direction and 5 nm in the axial direction. This method opens the route for real-time measurements of kinetics of macromolecules association, at a single molecule level, on very long time scales. (C) 2009 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3257269]