Abstract: There is provided a magnetic digital microfluidic system for performing an assay, the system comprising, abase member comprising at least one magnet disposed thereon; the magnet being configured to immobilise a droplet of reaction mixture doped with magnetic particles; and a droplet manipulator configured to be moveably mountable on the base member, said droplet manipulator comprising at least one test unit, each test unit comprising at least one mixing element for mixing the droplet of reaction mixture; wherein the mixing element is arranged to induce mixing as the droplet manipulator is moved in relation to the base member along an alignment path. There is also provided a method of performing an assay with the magnetic digital microfluidic system as disclosed herein.