Automatic Noncontact Extraction and Independent Manipulation of Magnetic Particles Using Electromagnetic Needle

Selective and independent manipulation of microparticles is important for a wide range of applications. Compared to other physical principles, magnetic field is promising due to its ability to penetrate most materials and affect only magnetic objects. However, in most noncontact magnetic manipulation systems, all particles in the workspace are moved simultaneously. This article reports an automatic single-source noncontact magnetic manipulation technique that can selectively extract individual magnetic particles from a population of similar particles and then independently manipulate the extracted particles. We use an electromagnetic needle to create a highly localized magnetic field to achieve the local addressability. The motion of single particles is controlled by adjusting the position of the electromagnetic needle using visual servoing, where two control laws, velocity and position control, have been developed. Experimental results show that a predefined velocity vector can be followed accurately with a directional error of 8.5
$^{\circ }$
and a norm error of 5
$\mu \text{m/s}$
. Similarly, a predefined path can be followed with a position error of 0.5
$\mu \text{m}$
. The capabilities of the proposed method has been demonstrated in four cases: selective extraction of a single particle from a population, separation of two magnetic particles with 10.6
$\mu \text{m}$
initial gap, independent manipulation of four particles, and targeted delivery of two particles onto two separate cells.