Impedance Analysis of Chitin Nanofibers Integrated Bulk Acoustic Wave Humidity Sensor with Asymmetric Electrode Configuration

Abstract

This paper fabricated a high-performance chitin nanofibers (ChNFs)-integrated bulk acoustic wave (BAW) humidity sensor with an asymmetric electrode configuration. The ChNFs were successfully prepared from crab shells and used as moisture-sensitive materials to compare the performance of quartz crystal microbalance (QCM) humidity sensors with symmetric and asymmetric electrode structures. The QCM humidity sensor with a smaller electrode area exhibited high sensitivity of 58.84 Hz/%RH, competitive response/recovery time of 30/3.5 s, and low humidity hysteresis of 2.5% RH. However, it is necessary to choose a suitable electrode diameter to balance the stability and sensitivity because the impedance analysis result showed that the reduction of the electrode diameter leads to a sharp decrease in the Q value (stability). Next, the possible humidity-sensitive mechanism of the ChNFs-integrated asymmetric n-m electrode QCM humidity sensor was discussed in detail. Finally, the reasons for the highest sensitivity of the asymmetric n-m electrode QCM humidity sensors having a smaller electrode diameter were analyzed in detail in terms of both mass sensitivity and fringing field effect. This work not only demonstrates that the chitin nanofiber is an excellent potential material for moisture detection, but also provides a new perspective for designing high-performance QCM humidity sensors.

Nanochitin/MXene Composite Coated on Quartz Crystal Microbalance for Humidity Sensing

“…which increases the repulsive force between the layers of MXene to prevent self-stacki Additionally, the hydrophilic nature of nanochitin provides more active sites for the midity-sensitive film [38]. The nanochitin/Ti3C2Tx MXene composite material was first p pared, and then, the deposition of the humidity-sensitive material onto the central reg of the QCM electrode was achieved through the drop-casting method.…”

“…The excellent hydrophilicity and dispersibility of nanochitin can help MXene to be better dispersed in an aqueous solution; it can be embedded in the layers of MXene, and nanochitin is usually positively charged, which increases the repulsive force between the layers of MXene to prevent selfstacking. Additionally, the hydrophilic nature of nanochitin provides more active sites for the humidity-sensitive film [38]. The nanochitin/Ti 3 C 2 T x MXene composite material was first prepared, and then, the deposition of the humidity-sensitive material onto the central region of the QCM electrode was achieved through the drop-casting method.…”

Influence of Front-End Electronics on Metrological Performance of QCM Systems

“…In this context, it is evident how monitoring other quantities related to the resonant behavior of the quartz can be beneficial, as it provides additional information about the interaction with the target substance. This is usually attained by exploiting different measurement techniques, ranging from impedance analysis [6][7][8][9][10] to simpler and lower-cost ones such as those based on frequency measurement associated with dissipation monitoring [11][12][13][14][15][16], or on a variant of oscillator-based systems, called QCM-R, recently proposed to simultaneously obtain a measurement of the dissipative behavior of the quartz [17][18][19][20][21].…”

“…This is usually attained by exploiting different measurement techniques, ranging from impedance analysis [ 6 , 7 , 8 , 9 , 10 ] to simpler and lower-cost ones such as those based on frequency measurement associated with dissipation monitoring [ 11 , 12 , 13 , 14 , 15 , 16 ], or on a variant of oscillator-based systems, called QCM-R, recently proposed to simultaneously obtain a measurement of the dissipative behavior of the quartz [ 17 , 18 , 19 , 20 , 21 ].…”