Ink property sensing on a printhead is described. In an example, a substrate for a printhead includes a cap layer having bores. Chambers are formed beneath the cap layer in fluidic communication with the bores. Fluid ejectors are disposed in at least a portion of the chambers. At least one ion-sensitive field effect transistor (ISFET) is disposed in a respective at least one of the chambers. An electrode is disposed in each of the chambers having an ISFET and capacitively coupled to said ISFET through a dielectric.