Abstract: A power transfer-based flexible sensing platform that can be used in a fluid environment includes at least one metallic thin film structure, with a polymeric encapsulation that protects the metallic thin film structure from the fluid environment, a smart hydrogel sandwiched between layers of the metallic thin film structure, the smart hydrogel being configured to swell or shrink in response to stimulus, and an AC power source or signal generator electrically connected to the at least one metallic film structure. The metallic thin film can include first and second U-shaped metallic thin film structures, each encapsulated, where the smart hydrogel is sandwiched between them. An AC power or signal source is electrically connected to one of the U-shaped structures, causing power to be inductively transferred to the other. Measurement of the induced power or other signal can be used to determine a concentration of an analyte in the fluid environment.