Magnetic bead receives viscosity resistance of fluid in the opposite direction of the potential well around a micromagnet, resulting in a position difference between the beads and potential well. When the position difference increases more than critical value, magnetic bead shows jumping motion by receiving repulsive force from micromagnet. In case of ellipse shaped micromagnet, the spatial magnetic force can be precisely controlled through the aspect ratio (AR) of the ellipse shaped micromagnet to control the position and height of the jump. Also, the position difference is determined by the size of micro-object which is conjugated to the magnetic bead because the viscous resistance increases according to the size. Thus, automatic size-based separation was performed using ellipse shaped micromagnet with various AR. Furthermore, a magnetophoretic device consisting of ellipse shaped micromagnet and active elements that enable the control of individual selective jumping motion and positioning of a micro-object is proposed. Based on a numerical simulation under various conditions, automatic separation or selective clustering of micro-objects according to their sizes is performed by parallel control and programmable manipulation. Programmable manipulation process composed of rotating magnetic field and local current using gating element. As marked with numbers in a certain position in the image (b), each part of the proposed circuit is operated in order of under a clockwise and counter-clockwise magnetic field. This method provides efficient control of the physical variables of micro-objects or cells and grouping with the desired size and number, which can be a milestone for a better understanding of the intercellular dynamics between clustered cells at the single-cell level for future cell-on-chip applications.
A unique magnetic potential energy distribution in the form of an asymmetric magnetic thin film around the gap is created and tuned in a controlled manner, regulated by the size ratio of the bead with a magnetic pattern. Hence, the aggregated beads are detached into single beads and transported in one direction in an array pattern. Furthermore, the simultaneous and accurate spacing control of multiple magnetic bead pairs is performed by adjusting the angle of the rotating magnetic field, which continuously changes the energy well associated with a specific shape of the magnetic patterns.
We develop a pseudo-diamagnetophoresis (PsD) mattertronic approach in the presence of biocompatible ferrofluids for programmable manipulation and local storage of single PsD holes and label-free cells. The PsD holes conduct along linear negative micro-magnetic patterns. Further, eclipse diode patterns similar to the electrical diode can implement directional and selective switching of different PsD holes and label-free cells based on the diode geometry. Different eclipse heights and junction gaps influence the switching efficiency of PsD holes for mattertronic circuitry manipulation and separation. Moreover, single PsD holes are stored at each potential well as in an electrical storage capacitor, preventing multiple occupancies of PsD holes in the array of individual compartments due to magnetic Coulomb-like interaction.