Fig. 1. Design and working principle of the tuning circuit–inspired wireless biochemical sensors.

(A) Schematic illustration of the stretchable, battery-free sensor and envisioned applications of the sensor system in detecting various biomarkers in bodily fluids. ISF, Interstitial fluid. (B) Photographs of a wireless sensor. (C) Equivalent circuit and flowchart for the signal conversion and transmission process of the sensor system. (D and E) Measured and simulated shift of resonance curves of a sensor with a DC reverse bias (from 200 to 400 mV; step: 50 mV). (F) Measured and simulated results of f_s as a function of the reverse bias (inset: zoom-in view).