Electrochromic Intelligent Visual Humidity Indication System

doi:10.15541/jim20230440

Abstract

Abstract:

In recent years, humidity sensors have attracted widespread attention from researchers in fields such as food safety and soil monitoring. Traditional humidity sensors exhibit the advantages of good stability and high sensitivity. However, most humidity sensing systems convert humidity signals into recognizable waveforms through wired connections and large external devices, making it impossible to achieve real-time visual monitoring of changes in humidity information. Currently, direct conversion of humidity information into visible color signals by eyes provides an ideal solution to the aforementioned problems but still lacks intelligent monitor capacity. This study integrated humidity sensors and electrochromic devices (ECDs) to prepare an intelligent visual humidity monitoring system. By converting humidity signals into voltage signals to drive ECDs, stable and reversible color change in the system could be achieved. The ECDs were prepared using tungsten trioxide (WO₃) as the negative electrode and zinc foil (Zn) as the positive electrode. Based on the output voltage of the humidity sensor, it achieves transitions between different working states, thereby generating color signals that can be observed by the naked eyes. Electrochemical performance and electrochromic performance of ECDs were tested and characterized by using a UV-visible spectrophotometer and an electrochemical workstation. Subsequently, the performance of the conditioning circuit was analyzed using an oscilloscope and a humidity generation platform. The results show that the intelligent electrochromic humidity indicator has good stability and rapid response performance, where the coloring time and fading time are only 7.5 s and 4.5 s, respectively. After 300 cycles, the optical modulation (ΔT) is basically maintained the same as the initial value, and the retention rate can reach more than 95%. Therefore, this visual humidity indication system which possesses novel design and simple structure has promising broad application in fields such as artificial intelligence and intelligent agriculture.

Key words: electrochromic device, humidity sensor, visual monitoring, artificial intelligence

CLC Number:

TQ174

ZHEN Mingshuo, LIU Xiaoran, FAN Xiangqian, ZHANG Wenping, YAN Dongdong, LIU Lei, LI Chen. Electrochromic Intelligent Visual Humidity Indication System[J]. Journal of Inorganic Materials, 2024, 39(4): 432-440.

Figures/Tables 10

Fig. 1 Characterization and performance of WO3 (a) SEM image of WO3; (b) XRD pattern of WO3; (c) XPS spectrum of WO3 thin film in the binding energy range of 0-1200 eV; (d) CV curves at different scanning speeds; (e) Transmission spectra of WO3 in bleached and colored states (photos of WO3 in different states in the illustration); (f) 2000 cycles performance of WO3

Fig. 2 Electrochromic performance of ECDs (a) Changes in transmittance at different voltages of 300-900 nm wavelengths; (b) Changes in corresponding transmittance at different voltages; (c) Response time of ECDs; (d) Stability of electrochromic performance of ECDs; (e) Optical images of ECDs at different voltages

Fig. 3 Relationship between humidity and output voltage of SHT30 humidity sensor

Fig. 4 Simulation results of Multisim (a) Voltage output at 100% RH; (b) Voltage output at 0 RH

Fig. 5 Performance of conditioning circuits (a) Circuit diagram of the conditioning circuits; (b) Circuit performance testing platform; (c) Voltage changes at different humidities; (d) Voltage stability at different humidities

Fig. 6 Performance testing of an electrochromic intelligent visual humidity indicator system (a) Structure of testing platform; (b) Color change of ECDs at different humidity conditions; (c) Transmittance under different humidity environments; (d) Stability performance of transmittance at different humidity conditions Colorful figures are available on website

Fig. S1 (a) CV curves of ECDs at different scanning speeds and (b) charge-discharge curves under different current densities

Video S1 Color changes of ECDs

Fig. S2 Output voltage at humidity of 10% RH, 40% RH, 70% RH, and 90% RH, respectively

Fig. S3 Circuit diagram for conditioning circuits

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