Droplet microactuator system

A droplet microactuator system comprising:

• (a) a cartridge comprising:
• (i) a droplet microactuator comprising a substrate comprising electrodes configured to conduct droplet operations in a gap formed by the substrate of the droplet microactuator and a second substrate;
• (ii) a cartridge reservoir and a fluid path from the cartridge reservoir into the gap;
• (iii) a mechanical mechanism, electrical mechanism, pressure source and/or vacuum source for forcing fluid through the fluid path;
• and
• (iv) a droplet in the gap comprising magnetically responsive beads;
• (b) a magnetic field source arranged to immobilize the magnetically responsive beads in the droplet in the gap during a droplet operation mediated by the electrodes;
• (c) an optical sensor configured in a sensing relationship with the droplet microactuator, such that the sensor is capable of sensing an optical signal from and/or an optical property of one or more droplets on the droplet microactuator;
• and
• (d) one or more processors electronically coupled to the droplet microactuator and programmed to:
• (i) control the droplet operations on the droplet microactuator, wherein the droplet operations conduct one or more droplet-based assay protocols using droplet operations comprising one or more electrowetting-mediated droplet operations and the droplet-based assay protocols comprise one or more electrowetting-mediated bead-washing protocols;
• and
• (ii) process electronic signals from the optical sensor.