Image courtesy of Lizhi Cao
Schematic A shows the chip layout, with circular nickel pads (blue), which can be magnetized by an external magnet flanked by interdigitated gold electrodes (red). Schematic B shows paramagnetic beads introduced to the chip surface by microfluidics and loaded onto the magnetic pads by magnetic manipulation, facilitating the formation of bead surface tethers via antibody-antigen interactions. Schematic C shows interactions probed by application of sufficient nDEP force to displace non-specifically bound beads, but not specifically bound beads. Schematic D shows how the devices are fabricated.