Micro manipulation of superparamagnetic particles using magneto-optic tweezers

We have developed a magneto-optic tweezers that offer new experimental possibilities when laser tweezers were traditionaly used. The magneto-optic tweezers combine a multi-trap optical tweezers based on acousto optic deflectors and homogeneous magnetic field which direction and magnitude can be time modulated in arbitrary fashion. Superparamagnetic beads that are readily available from several commercial sources are used as trap handles. They can be manipulated using optical tweezers in a well known way. By applying magnetic field additional repulsive or attractive interaction between the particles can be induced, giving rise to new micromanipulation possibilities. Several examples of how magneto-optic traps can be used in colloidal physics reasearch and potential applications in biophysics and microfluidic systems are presented.