Sensing a property of a fluid

A printhead comprising:

• an orifice plate;
• a nozzle formed in the orifice plate;
• a fluid ejector;
• a fluid chamber formed between the fluid ejector and the orifice plate;
• a fluid property sensing device disposed to detect a property of fluid contained in the fluid chamber, wherein the fluid property sensing device includes:
• an ion-sensitive field effect transistor (ISFET) having a gate, a source, and a drain;
• a metal plate exposed to the fluid chamber;
• a switching layer in contact with the metal plate, wherein a resistance state of the switching layer is to be modified through application of an electrical field through the switching layer, and wherein the switching layer is to retain the resistance state following removal of the electrical field;
• and
• an electrode positioned in spaced, aligned relation to the metal plate, wherein the electrode is capacitively coupled to the gate of the ISFET.