Patent ID: 8858432

Claim:
A system comprising: an ingestible event marker (IEM) composition configured to emit a signal upon contact with a target physiological site and does not include an active agent; wherein the IEM comprises: a first battery structure comprising: a first cathode; a first anode, wherein the first cathode and the first anode are made at least in part from dissimilar materials selected to provide a voltage potential difference when the first cathode and the first anode contact an electrolyte made up at least in part by fluid present at the target physiological site; a first chamber containing the first cathode and the first anode, wherein the first chamber defines at least one opening providing for entry and exit from the first chamber of the fluid; and a second battery structure comprising: a second cathode; a second anode, wherein the second cathode and the second anode are made from dissimilar materials selected to provide a voltage potential difference when the second cathode and the second anode contact the electrolyte; and a second chamber containing the second cathode and the second anode, wherein the second chamber defines at least one opening providing for entry and exit from the second chamber of the fluid; and a signal receiver configured to receive a signal produced by the IEM, wherein the receiver is sized to be stably associated with a living subject in a manner that does not substantially impact movement of said living subject.