Physiological sensor patch for making complex measurements of bioimpedance

A system for characterizing a patient, comprising:

• a substrate configured to be worn on a region of tissue of the patient;
• a first electrode and a second electrode disposed along an annular ring, wherein the first electrode and the second electrode are connected to the substrate and configured to be attached to the patient above the region of tissue;
• a plurality of strain gauges, each strain gauge comprising a metal trace patterned across a width of the annular ring;
• and
• an electrical system connected to the substrate and configured to be worn entirely on the patient's body, the electrical system in electrical contact with both the first and second electrodes and configured to:
• (1) inject an alternating electrical current at a plurality of different frequencies through the first electrode and into the region of tissue, and
• (2) measure a set of electrical signals from the region of tissue through the second electrode, with each electrical signal in the set measured after injecting the alternating electrical current at a unique frequency into the region of tissue;
• and
• a processor in communication with the electrical system configured to receive the set of electrical signals, receive a signal from the strain gauge, process the set of electrical signals and the signal from the strain gauge, and determine swelling beneath a surface of the region of tissue.