A semi flexible integrated wireless humidity sensor

A semi flexible integrated LC sensor capable of sensing humidity wirelessly in ppm level has been fabricated. The sensor forms a resonant circuit consisting of a rectangular planar inductor connected in parallel to a moisture-dependent capacitor. The sensor is fabricated by Metal oxide (γ-Al₂O₃) thin film by sol-gel method. Rectangular planar inductor has been fabricated on copper cladded polyimide substrate for flexibility. An interrogator coil is inductively coupled to the sensor inductor and remotely tracks the shift in resonance frequency and quality factor of the sensor by impedance analyzer (4294A Agilent). The frequency sensitivity of the integrated sensor for a moisture range of 8 to 221 ppm is nearly 712.9 ppm/Hz.