A device comprising: a first zone comprising an attachment site; a first pathway; a second pathway and a means for creating a second medium comprised of aqueous microdroplets in a carrier; a microdroplet manipulation zone comprising: a first composite wall comprised of a first transparent substrate; a first transparent conductor layer on the substrate; a photoactive layer activated by electromagnetic radiation; and a first dielectric layer on the photoactive layer; a second composite wall comprised of a second substrate; a second conductor layer on the substrate; and optionally a second dielectric layer on the conductor layer; an A/C source; a source of first electromagnetic radiation; means for manipulating the points of impingement of the electromagnetic radiation on the photoactive layer; an detection zone disposed downstream of the microdroplet manipulation zone or integral therewith; and a fluorescence or Raman-scattering detection system.