We present a multiplex method, based on microscopic programmable magnetic traps in zigzag wires patterned on a platform, to simultaneously apply directed forces on multiple fluid-borne cells or biologically inert magnetic micro-/nano-particles. The gentle tunable forces do not produce damage and retain cell viability. The technique is demonstrated with T-lymphocyte cells remotely manipulated (a la joystick) along desired trajectories on a silicon surface with average speeds up to 20 μm/s.

A platform of discrete microscopic magnetic elements patterned on a surface offers dynamic control over the motion of fluid-borne cells by reprogramming the magnetization within the magnetic bits. T-lymphocyte cells tethered to magnetic microspheres and untethered leukemia cells are remotely manipulated and guided along desired trajectories on a silicon surface by directed forces with average speeds up to 20 microm/s. In addition to navigating cells, the microspheres can be operated from a distance to push biological and inert entities and act as local probes in fluidic environments.

Remote manipulation of fluid-borne magnetic particles on a surface is useful to probe, assemble, and sort microscale and nanoscale objects. In this paper, fields emanating from magnetic domain walls in zigzag wires as well as from magnetization distributions in notched Co 0.5 Fe 0.5 wires patterned on a silicon surface are shown to act as effective traps for such objects. Weak (∼100 Oe) in-and out-of-plane external magnetic fields modify the energy landscape, allowing for the entrapped objects to be remotely maneuvered along predetermined routes across the surface while the magnetization profiles at the wire vertices and notches remain stationary. In calculating the forces, the net magnetic field and its spatial distribution are determined by modeling the wire magnetization using micromagnetic simulation or by approximating the trap as a point source of fields. The applicability of these models to particle manipulation under the experimental conditions is discussed.

A major challenge to achieving positional control of fluid borne submicron sized objects is regulating their Brownian fluctuations. We present a magnetic-field-based trap that regulates the thermal fluctuations of superparamagnetic beads in suspension. Local domain-wall fields originating from patterned magnetic wires, whose strength and profile are tuned by weak external fields, enable the bead trajectories within the trap to be managed and easily varied between strong confinements and delocalized spatial excursions that are described remarkably well by simulations.

We present an all-magnetic scheme for the assembly and study of magnetic dipoles within designed confinement profiles that are activated on micro-patterned permalloy films through a precessing magnetic field. Independent control over the confinement and dipolar interactions is achieved by tuning the strength and orientation of the revolving field. The technique is demonstrated with superparamagnetic microspheres field-driven to assemble into closely packed lattice sheets, quasi-1D and other planar structures expandable into dipolar arrays that mirror the patterned surface motifs.