A device for manipulating a magnetic coupling force across tissue in response to a monitored coupling force is described. The device includes a magnetic field source assembly that includes at least one fixed magnet and a rotatable magnet positioned within a cavity defined by the fixed magnet that provide an external magnetic field source for providing a magnetic field across tissue. An actuation assembly is operatively connected to the magnetic field force assembly. A sensor is provided that senses a magnetic coupling force and communicates changes therein to a controller which directs the accuation assembly to adjust the speed of rotation of the rotatable magnet in response to the sensed changes in magnetic coupling force to effect a change of magnetic flux generated by the rotatable magnet.
