On-chip control of magnetic particles

We describe an on-chip system to control the actuation of micrometer- and nanometer-sized magnetic particles. Orthogonal conducting microwire arrays are used to induce magnetic fields with highly localized peaks and strong local gradients. These fields are then applied in actuation experiments to generate defined particle movement with micrometer precision. We examine different types of current sequences to efficiently move and separate the particle cloud on the chip without the use of external magnets. The final protocol allows efficient and reliable control over the particle cloud's position minimizing the loss of particles during the individual switching steps. Schematic of a microwire chip controlling a cloud of particles (black). The chips are processed on silicon (blue). The microwires consist of Au (yellow) and are insulated with an oxide nitride passivation layer (green transparent).