In this work, we describe proximity sensors using functional coatings as sensing elements. The planar inductor-capacitor resonant circuit is fabricated by conventional PCB fabrication techniques and also by using low cost drop-on-demand inkjet printing technology. The permittivity and conductivity is changing in the system as a function of humidity, which simulates the presence of a body. This change in turn modifies the resonant frequency of the sensor. The performance of the fabricated proximity sensors are good, especially using the PCB resonant circuit and the gypsum/sodium-hydrogen titanate nanowire composites as sensitizing elements.
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