Manipulation of beads in droplets and methods for manipulating droplets

A method of circulating magnetically responsive beads within a droplet in a droplet actuator, the method comprising:

• (a) providing a droplet actuator, comprising:
• (i) a plurality of droplet operations electrodes configured to transport the droplet;
• and
• (ii) a magnetic field comprising a uniform region of the magnetic field provided by one or more magnets and present at a plurality of droplet operations electrodes;
• (b) providing a bead-containing droplet on the droplet actuator in the presence of the uniform region of the magnetic field;
• and
• (c) circulating beads in the droplet during incubation by conducting droplet transport operations on the droplet using the plurality of droplet operations electrodes within the uniform region of the magnetic field, wherein droplet operations do not allow magnetically responsive beads to be introduced into a region of the magnetic field which is sufficiently non-uniform to cause bead clumping, thereby resulting in a more homogenous distribution of the beads in the droplet, and wherein the droplet is maintained at a temperature suitable for incubation of the contents of the droplet.