An ingestible event marker comprises a support； a control circuit physically associated with the support to control the ingestible event marker； a first electrochemical material physically associated with the support and electrically coupled to the control circuit； a second electrochemical material electrically coupled to the control circuit and physically associated with the support at a location different from the location of the first material such that the first and second electrochemical materials are electrically isolated from each other and a membrane. The first electrochemical material is dissimilar from the second electrochemical material, and the first and second electrochemical materials are configured to produce an actual dipole having a predefined dipole length. The membrane is physically associated with the support and positioned relative to the first electrochemical material and the second electrochemical material to produce a virtual dipole having a length defined by the membrane. The virtual dipole length is larger than the actual dipole length and he first and the second electrochemical materials are configured to generate a voltage potential to power the control circuit when the first and the second electrochemical materials come into contact with an electrically conductive liquid at a target physiological site. A system comprising: an active agent； and the above described ingestible event marker is further disclosed.
