Methods and apparatus for high throughput microdroplet manipulation

The present invention provides methods and apparatus for manipulating and interrogating the contents of large numbers of microdroplets in parallel on a surface of a microfluidic chip. According to one aspect of the invention a method is provided for manipulating and inspecting microdroplets on a microfluidic chip by optically- mediated electrowetting (oEWOD), the method comprising forming, using a first optical assembly, a plurality of oEWOD traps on a surface of the chip and forming, using a second optical assembly, a second array of oEWOD traps on the surface of the chip, and making an adjustment to the first optical assembly whilst one or more of the microdroplets are held in place by second array of oEWOD traps. Apparatus comprising a microfluidic chip and first and second optical assemblies is also provided.