Cells in suspension or biologically important macromolecules in solution can be labelled with crystallin magnetically lattices. This enables their processing, manipulation and detection by applying a magnetic field. However, the magnetic field must be dynamic and cannot be a traditional DC field. DC fields can only produce field gradients close to poles, where magnetic particles can be gathered passively. They cannot move actively and three-dimensionally, which is the prerequisite for the proper processing of marked objects.
Dynamic fields obey the first Maxwell equation:
First Maxwell-Equation (integral (remote) form)
The second part of the sum on the right side can be neglected, due to very small displacement currents. This makes the H field independent from material constants, which allow the system to be applied with only marginal losses in media such as blood, salty water etc.