Correlation function analysis combined with optical tweezers technique is proposed for studying of magnetic
interaction influence on statistical properties of microparticles Brownian motion in liquid. It is shown that
autocorrelation function of Brownian particle displacements from optical trap center contains information about
particles rotation frequency in rotating magnetic field. Powerful method based on correlation analysis to detect
the interaction between paramagnetic microparticles in a constant magnetic field is suggested. Experimental
results show that magnetic interaction changes cross-correlation function of nanometer displacements of two
optically trapped particles in a constant external magnetic field.
Double optical tweezers combined with active rheology approach are suggested for dynamic monitoring of the
red blood cell elastic properties. Frequency dependence of the phase difference in the forced movement of the
erythrocyte opposite edges appeared to be highly dependent on the rigidity of the cellular membrane. Cell
relaxation time value is suggested as an effective parameter determining the state of the cell. Photo-induced
effects caused by optical trapping are analyzed.
A novel approach to probe viscoelastic properties of cells based on double trap optical tweezers is reported. Frequency dependence of the tangent of phase difference in the movement of the opposite erythrocyte edges while one of the edges is forced to oscillate by optical tweezers appeared to be highly dependent on the rigidity of the cellular membrane. Effective viscoelastic parameters characterizing red blood cells with different stiffnesses (normal and glutaraldehyde-fixed) are determined. It is shown that the photo-induced effects caused by laser trapping at the power level used in the experiments are negligible giving the possibility to use the offered technique for dynamic monitoring of soft materials viscoelastic properties.