Optical trapping, also known as optical tweezers, is mainly used in the biophysical field for performing very precise mechanical force measurements. Compared to Atomic Force Microscopy (AFM), a trapped microsphere is the equivalent of the cantilever tip as transducer for mechanical stressing and force measurement. Some strategic advantages for the manipulation of soft materials, living cells, and micro-organisms are the following:
In our group, we have a computer-controlled, 3D positioned twin optical tweezers, relying on a fs Ti:Sapphire laser as trapping source. The optical force on microspheres is calibrated using the biased power spectrum calibration technique, using a 3-axes piezoelectric stage for the precise determination of the optical forces. We have already trapped yeast cells, polystyrene beads, Nipam microgels, nanofibers, and liposomes. Current lines of research focus on the study of the mechanical properties of bilipidic membranes, the elasticity of single nanofibers, together with the improvement of the experimental trapping effectiveness on living objects.