## 1 Introduction
In 2018, [PERSON] realized a capacitive humidity sensor with a moisture-sensitive film thickness of 1.5 um and 3.0 um. The experimental comparison found that the sensor's response time with a thickness of 1.5 um was shorter than 3.0 um, shortened from 35 s to 5 s. Still, the sensitivity was reduced from 299.9 pF/% RH to 178.6 pF/%RH [33]. In 2019, [PERSON] proposed a two-step method to optimize the layout of traditional serpentine film heaters. The substrate area within 96.4% temperature uniformity increases by more than five times compared to the conventional serpentine heater. The optimized serpentine heater realizes a coverage ratio as high as 86.64% on a rectangular membrane [34]. It can be seen from the above studies that most of the current work starts with heating the sensor and changing the structure of the sensor unit to improve the performance of the sensor in complex environments. However, for capacitive humidity sensors, it is contradictory to improve sensor sensitivity and dynamic response time simultaneously. According to the sensor's moisture-sensing principle, increasing the sensor's moisture-sensing area by changing the structure of the sensor unit and the moisture-sensing layer will significantly increase the fundamental capacitance value of the sensor and amplify the sensor's signal to be measured. Nevertheless, the time for water molecules to travel in the moisture-sensitive material is correspondingly increased. Although the sensor's sensitivity is improved, its dynamic response time is reduced. Likewise, by lowering the moisture-sensitive area of the sensor, the opposite effect occurs. This motivates research on optimizing the sensor structure design while considering the sensitivity and dynamic response performance. In addition, in the research work on heating the humidity-sensitive structure, although the temperature rise significantly improves the sensor performance, the heating area is small, and the heat transfer is not uniform, which affects the high-performance humidity measurement. Given the above problems, this paper takes the interdigital capacitive humidity sensor with better dynamic performance as the research object. On the one hand, based on the conformal mapping method [35] and [PERSON]'s second diffusion law [36], the sensitivity and dynamic response theoretical model of the humidity sensor is established. The key structural parameters that affect the performance of the sensor are identified, and the accuracy of the theoretical model is verified through simulation modeling. On the other hand, an objective function that takes into account the sensitivity and dynamic response performance of the sensor is constructed, and the optimized design of the sensor structure is realized by using a PSO (Particle Swarm Optimization) algorithm [37]. At the same time, a new sensor heating-electrode structure is designed, which significantly increases the electrode heating area and heat transfer uniformity, and further improves the sensor sensitivity and dynamic response performance. The main contributions of this paper are as follows:  
* Construct a sensitivity and dynamic response theoretical mathematical model of the interdigital capacitive humidity sensor, which obtains the interaction relationship between the sensor performance and various structural parameters;
* Optimize the key structural parameters of the sensor while taking into account the sensitivity and dynamic response performance;
* Design the sensor heating electrode structure and heating strategy to significantly increase the heating area and uniformity while effectively reducing system power consumption. The rest of this paper is organized as follows. Mathematical Modeling is presented in Section 2. Section 3 describes the Optimizing Analysis Methods proposed in this paper. The last two parts, Section 4 and Section 5, are evaluation and conclusions, respectively.