US Patent 9476856 Droplet-based affinity assays

A method of detecting a target analyte in a sample, including executing electrowetting-mediated droplet operations and thereby: combining one or more immunoassay reagent droplets comprising magnetically-responsive beads having affinity for the target analyte with one or more sample droplets potentially comprising the target analyte to yield a first combined droplet; beginning with the combined droplet, effecting a droplet-based washing protocol to wash the magnetically-responsive beads to yield a first washed droplet comprising the washed magnetically responsive beads; and combining the droplet comprising the washed magnetically responsive beads with a droplet comprising a reporter molecule having affinity for target analyte captured on the magnetically-responsive beads to yield a second combined droplet; beginning with the second combined droplet, effecting a droplet-based washing protocol to wash the magnetically-responsive beads to yield a second washed droplet comprising the washed magnetically responsive beads; detecting a signal from the second washed droplet which corresponds to the presence, absence and/or quantity of the analyte in the sample.