This is a conceptual design of MAP-nDEP tweezers. a) Schematic of chip layout: Circular magnetic nickel pads (blue) were flanked by interdigitated gold electrodes (red). b) Paramagnetic beads were introduced to chip surface by microfluidics and loaded onto the magnetic pads by magnetic manipulation, facilitating the formation of bead-surface tethers via antibody-antigen interactions. c) Interactions probed by application of sufficient nDEP force to displace non-specifically bound beads, but not specifi cally bound beads. d) Microfabrication process.