A method of assembling a droplet actuator assembly (1400, 1500), the method comprising: providing: a mount structure (1410, 1510); a magnet assembly, comprising a first substrate configured to accommodate one or more magnets adapted, in use of the droplet actuator assembly (1400, 1500), for emitting a magnetic field affecting a magnetically responsive bead present in the droplet actuator assembly (1400, 1500); and a droplet actuator, comprising a second substrate upon which is an arrangement of electrodes adapted, in use of the droplet actuator assembly (1400, 1500), for emitting an electric field affecting a droplet present in the droplet actuator assembly (1400, 1500); and attaching to the mount structure (1410, 1510) the droplet actuator and the magnet assembly, wherein at least one of the droplet actuator and the magnet assembly is removably attached to the mount structure (1410, 1510); wherein attaching at least one of the droplet actuator and the magnet assembly to the mount structure (1410, 1510) further comprises using at least one fastener mechanism selected from a list consisting of: a fastener; a slot; a recessed tray; a spring loaded mechanism; a post; and a fitting; and wherein the at least one fastener mechanism serves to orient the first substrate and the droplet actuator so as to align magnets on the magnet assembly with appropriate electrodes or electrode paths on the droplet actuator. providing: a mount structure (1410, 1510); a magnet assembly, comprising a first substrate configured to accommodate one or more magnets adapted, in use of the droplet actuator assembly (1400, 1500), for emitting a magnetic field affecting a magnetically responsive bead present in the droplet actuator assembly (1400, 1500); and a droplet actuator, comprising a second substrate upon which is an arrangement of electrodes adapted, in use of the droplet actuator assembly (1400, 1500), for emitting an electric field affecting a droplet present in the droplet actuator assembly (1400, 1500); and a mount structure (1410, 1510); a magnet assembly, comprising a first substrate configured to accommodate one or more magnets adapted, in use of the droplet actuator assembly (1400, 1500), for emitting a magnetic field affecting a magnetically responsive bead present in the droplet actuator assembly (1400, 1500); and a droplet actuator, comprising a second substrate upon which is an arrangement of electrodes adapted, in use of the droplet actuator assembly (1400, 1500), for emitting an electric field affecting a droplet present in the droplet actuator assembly (1400, 1500); and attaching to the mount structure (1410, 1510) the droplet actuator and the magnet assembly, wherein at least one of the droplet actuator and the magnet assembly is removably attached to the mount structure (1410, 1510); wherein attaching at least one of the droplet actuator and the magnet assembly to the mount structure (1410, 1510) further comprises using at least one fastener mechanism selected from a list consisting of: a fastener; a slot; a recessed tray; a spring loaded mechanism; a post; and a fitting; and wherein the at least one fastener mechanism serves to orient the first substrate and the droplet actuator so as to align magnets on the magnet assembly with appropriate electrodes or electrode paths on the droplet actuator.