Sensitivity evolution and enhancement mechanism of porous anodic aluminum oxide humidity sensor using magnetic field

Massive, eco-friendly, and facile fabrication of multi-functional anodic aluminum oxides: application to nanoporous templates and sensing platforms

“…It is expected that the performances of our humidity sensors would be further improved by optimizing dimensional properties of the AAO and electrodes. 28,70,72 These results represent a superior applicability of our devices such that one can choose the structure of the humidity sensors with respect to the interesting region of the RH. Moreover, our strategy, excluding the procedure for removing the barrier oxide layer, also exhibits another advantage in terms of the simplicity about device fabrication.…”

“…Sensor-A showed quite linear responsive variations of capacitance in the intermediate RH regions (40-70% under 100 kHz and 60-90% under 1 MHz), whereas the capacitance were varied only in the high RH region ($75%) in Sensor-B, which was comparable to the previous reports at relatively high frequencies. [22][23][24][25][26][27] The barrier oxide layer in Sensor-A might play an important role for storing the humidity inside the nanopores more effectively resulting in the linear variation of the capacitance even in the relatively low RH region without applying sophisticated add-ons, 70 for examples magnetic eld 28 or water-sensitive sol-gel materials (e.g., polyethylene glycol).…”

“…[1][2][3][4] Aer the report on the two-step anodization resulting in a distinct improvement of the structural periodicities over the extended spatial regime, 5,6 anodic aluminum oxides (AAOs) have been widely adopted in diverse research elds, such as representative nanoporous templates for one-dimensional (1-dim.) nanostructures, [7][8][9][10][11][12][13] membrane lters, [14][15][16][17] evaporation/etching masks, 18-21 humidity sensors, [22][23][24][25][26][27][28] energy storage devices, [29][30][31][32] and bio-applications, [33][34][35][36] etc. These applications excluding surface treatments require AAOs with freestanding forms, i.e., separation from aluminum (Al) substrate, thus various strategies have been developed in the viewpoints of not only AAO fabricating (anodizing) but also AAO separating procedure.…”

Effect of oxalic acid concentration on the magnetically enhanced capacitance and resistance of AAO humidity sensor

“…Chen el al. [16] also showed that the magnetic field could promote the bonding of first physisorbed water molecules with chemisorbed molecules to increase their contribution to the dielectric constant and capacitance. The sensitivity of capacitance not only increased at low RH but also at high RH due to the water molecules with more orderly arrangement on the surface of AAO.…”

“…The system was combined by two chamber, a computer, LCR meter and commercial humidity sensor and it was reported in our previous work [16]. The first chamber was accessed the flows of dry air and wet air to adjust the relative humidity, then the controllable and stable humidity level (15%~80%) was achieved in second chamber and measured with a commercial sensor (Lascar, EL-USB-@-LCD, UK).…”