Chemotactic Magnetic Bead Chain Chemical Probe

Systems and methods are provided for detecting or measuring binding affinity between different compositions. The methods include contacting one or more magnetic beads having a surface including a first composition with a substrate having a surface including a second composition; applying a rotating magnetic field to the one or more magnetic beads effective to cause the one or more magnetic beads to move across the surface of the substrate; measuring the movement of the one or more magnetic beads across the substrate surface to determine a translational velocity; and determining a binding affinity between the first and second compositions from the translational velocity.