## 1 Introduction  
In meteorological monitoring, weather bureaus and marine monitoring applications rely on accurate humidity sensing. The accuracy of meteorological detection is directly related to the timeliness of disaster prevention. For this reason, humidity sensors that can be used in a wide humidity range and under conditions of sudden changes in temperature and humidity have received extensive attention [1; 2; 3; 4; 5]. Humidity sensors can be divided into resistive and capacitive [6]. Resistive humidity sensors tend to have lower manufacturing difficulty and are usually cheaper than capacitive humidity sensors. However, their shortcomings including poor sensing range, long response time, and low measurement accuracy widely limit their applications [7]. In contrast, the interdigitated electrode (IDE) capacitive humidity sensor has the characteristics of lower consumption, large output signal, and fast response time [8; 9]. Consequently, most current humidity sensors prefer to use the IDE structure. It can be seen from the principle of capacitive sensors that the output value, sensitivity, response time, and other properties of the sensor are related to the structural and material parameters [10; 11]. These parameters mainly affect the size and dielectric coefficient of the sensor. Generally speaking, the larger the dielectric coefficient, the better the capacitive response. The thinner the sensitive layer, the worse the sensitivity, but the shorter the response time. Recently, the effects of sensor structures on humidity-sensing characteristics have been reported from various perspectives [9; 12], but few works consider the effects of the film thickness. Since both capacitance and response time are related to thickness, thickness will inevitably affect the properties of the sensor [13; 14]. During the past decade, a novel type of 2D transition metal carbide and carbon-nitrogen-labeled MXene families have been widely researched for their potential applications in humidity sensing, food analysis, clinical detection, and many other fields [15; 16; 17; 18; 19; 20]. Similar to the common characteristic of 2D materials [21], many MXene-based humidity sensors have been demonstrated to have good conductivity [22], chemical stability [23], and fast-response properties [24]. From the mechanism analysis, the hydrophilic functional group on MXene adsorbs water molecules in the air, thus changing its physical characteristics, which means that it can be used as a humidity sensor [25]. Experimental results have also indicated that MXene is a good choice for humidity-sensitive materials [26; 27]. For example, it has been reported that the response/recovery rate of a Ti\({}_{3}\)C\({}_{2}\)/Ag-based humidity sensor can reach 80/120 ms [28]. Additionally, many studies have shown that MXene-based humidity sensors also have good sensitivity, even reaching 317% at 90% relative humidity (RH) [29; 30; 31]. However, most researchers only analyzed the humidity-sensing properties of MXene based on the experimental results. Few attempts have been made on the MXene humidity-sensing mechanism through theoretical analysis [32; 33; 34]. Note that the theoretical models for other humidity-sensitive materials have been established, which facilitates the optimization of the sensor parameters [14; 35]. In view of this, this paper aims to fill this gap through theoretical modeling and simulation. This paper investigates the static and dynamic properties of MXene-based IDE capacitive humidity sensors through theoretical modeling and simulation. Coupled with the thickness structure of the sensors and the humidity-sensing properties of MXene, the static and dynamic properties of the sensor are analyzed by [PERSON]'s law and other theories, and the effects of parameters on the humidity sensing properties are analyzed by simulation. The accuracy of the model is further demonstrated by the explanation of the humidity sensing mechanism.