We present an experimental demonstration of a method using optical tweezers proposed by Fischer and Berg-Sorensen
for measuring viscoelasticity using optical tweezers. It is based on a sinusoidal oscillation of the liquid in combination
with force measurements using optical tweezers. We verify the method by applying it to measurements in water, glycerol
and polyethylene oxide (PEO).
We are exploring a biological application of optical tweezers with fluorescence imaging for microrheometry.
Measurement of the power spectrum of Brownian motion of a trapped probe particle or vesicle provides information on
the viscoelastic properties of the surrounding medium which can change in response to cellular processes or the effect of