Various embodiments disclosed relate to a resonator system that can be used to monitor status of tissue. A passive resonant sensor having an inductive element and a capacitive element can be implemented in a patch format and attached to tissue. The patch and resonant sensor can be structured such that, when contacting the tissue, dielectric of the contacted tissue contributes to capacitance of the resonant sensor to affect a resonant frequency of the resonant sensor. Additional apparatus, systems, and methods can be implemented with variations in a patch-resonant sensor structure.
