Patent ID: 7305319

Claim:
A system for applying a force to and sensing a position of a mechanically unattached probe to provide three-dimensional control of position and velocity of the probe and an estimate of three-dimensional forces acting on the probe in its physical environment, the system comprising: (a) a mechanically unattached probe comprising a paramagnetic bead for applying force to a specimen; (b) n magnetic poles, n being an integer of at least four, the poles being geometrically arranged with respect to each other for applying force in three dimensions to the probe and thereby for effecting movement of the probe in three dimensions; (c) at least one magnetizing coil being coupled to the poles for magnetizing the poles to apply magnetic force to the probe wherein, when magnetized, each magnetic pole applies force to the probe in a direction towards the magnetized pole; (d) an optical tracker for tracking the position of the probe in three dimensions and producing measured position feedback; (e) a three-dimensional motion controller receiving as input a probe position set point and being coupled to the optical tracker and the at least one magnetizing coil, the three-dimensional motion controller being adapted to minimize an error between the set point and the measured position feedback by driving the at least one magnetizing coil to produce a magnetic force on the probe to move the probe in three dimensions to reduce the error, thereby forming a closed feedback loop to control the position of the probe; and (f) means for determining a viscoelastic property of the system under test using the tracked probe position and applied force measurements.