Single-shot wideband active microrheology using multiple-sinusoid modulated optical tweezers

Abstract

Optically trapped colloidal probes have been widely used for active microrheology of viscoelastic fluids over the last decade. A significant issue which arises is measurement of complex viscoelastic parameters over a wide frequency range and a short time. We use a combination of square and sinusoidal waves to spatially modulate the trapped probe over a frequency range spanning five decades, and use the phase response to calculate complex viscoelastic parameters with high signal to noise in a little over three minutes. We test our method over a wide variety of linear viscoelastic samples at different concentrations, and find good agreement of the measured parameters with known values.