1. A device for detecting phosphorylation of an array of proteins, comprising: an array of sensors, each sensor comprising one ion-sensitive field effect transistor (ISFET); a layer of first material disposed over the array of sensors and having formed therein a plurality of microwells, each microwell disposed over at least one of the ISFETs; and wherein each microwell comprises a polypeptide comprising a test amino acid sequence and an affinity tag, and a binding agent that recognizes the affinity tag attached to a surface of the microwell.