FPGA-based real-time position-clamp control in optical tweezers, The Sequel: doi:10.1063/1.3257693 (first part here)

Optical tweezers use light to trap dielectric particles in an approximately harmonic potential. If the position of the bead is X, the position of the trap Xtrap, and the stiffness of the trap k then the equation of motion looks like this: where Beta is the drag coefficient and Ft is a random white-noise thermal [...]

Wallin, A.E., Salmi, A., Tuma, R. (2007). Step Length Measurement–Theory and Simulation for Tethered Bead Constant-Force Single Molecule Assay. Biophysical Journal, 93(3), 795-805. DOI: 10.1529/biophysj.106.097915 A lot of single molecule experiments are carried out in the configuration shown above. The idea is to mechanically probe a bio-molecule (such as DNA or RNA) or find out [...]