A surface acoustic wave humidity sensor based on electrosprayed silicon-containing polyelectrolyte

A silicon-containing polyelectrolyte with crosslinking structure was deposited on a surface acoustic wave (SAW) resonator operating at 433 MHz to construct a humidity sensor by the method of electrospray and heat treatment. Morphology observation by scanning electron microscopy and atomic force microscopy revealed that the polymer film so obtained was uniform and smooth. The frequency response to humidity of the SAW sensor over the range of 11–97%RH was investigated at room temperature. The effect of the electrospray parameters on humidity response of the sensor was examined including electrospray time, concentration of the electrospray solution. It was found that the sensor exhibited good sensitivity over a wide humidity range (∼−0.4 kHz/%RH), fast (∼10 s for adsorption and desorption) and reversible response. Moreover, it showed high stability under humid environment. The relationship between the polymer structure and its frequency sensing properties was also explored.