## 2 Materials and Methods
### Data Acquisition  
To achieve effective signal acquisition in flexible tactile systems, [PERSON] et al. [55] developed an integrated intelligent tactile system for a humanoid robot, emphasizing the importance of real-time data collection with minimal system interference. Building on this concept, we designed a signal acquisition circuit based on a flexible sensor array, as depicted in Figure 3. This design aims to achieve real-time multi-channel data collection while preserving the flexibility of the hand. The circuit consists of five main components, as illustrated in Figure 3a: a sensor array module, data acquisition module, microcontroller (MCU) module, data transmission module, and PC data receiving module. We use nine flexible pressure sensors to form a flexible pressure sensor array, with the sensors distributed across the five fingers of a hand, as shown in Figure 3f. Figure 3g presents a photograph of the sensor array. The nine pressure sensors are evenly distributed across the five fingers of the right hand. Compared to having just one or two sensors on a single finger, this arrangement significantly improves the accuracy and flexibility of tactile perception. The multi-point sensor design allows for finer detection of pressure differences between the fingers, providing more accurate tactile feedback, which is especially crucial for robotic grasping and object manipulation tasks. Sensors distributed across multiple fingers better simulate the tactile perception of the human hand, enhancing the system's precision in spatial awareness, object recognition, and classification. Additionally, the distributed design of the sensors increases the system's fault tolerance, ensuring stable tactile feedback even if one sensor fails [56; 57; 58]. The sensor array is responsible for converting pressure signals into electrical signals. These signals are collected by the data acquisition circuit (Figure 3c) and transmitted to the MCU module (Figure 3d). We selected the STM32F104C876 microcontroller (STMicroelectronics, Geneva, Switzerland) from STMicroelectronics, which utilizes its built-in analog-to-digital converter (ADC) module to convert analog signals into digital signals through programming. Figure 2: Analysis and performance characterization of the flexible sensor. (**a**) A schematic diagram of the flexible sensor. (**b**) Response characteristics of the sensor under different pressures. (**c**) The performance of the sensor under varying frequency pressures. (**d**) The current–voltage curve of the sensor. (**e**) Response and recovery time curves of the sensor. (**f**) The cycling stability test of the sensor. Data transmission employs the asynchronous serial communication protocol (UART), facilitating the transfer of data from the microcontroller (MCU) to the PC data receiving end. UART communication utilizes two data lines, with each line connecting devices via RX (receive) and TX (transmit) pins, where the RX and TX pins are cross-connected between the two devices. Figure 3b presents a photograph of the serial-to-USB adapter based on the CH340 chip used, which is part of the STM32 development kit. Figure 3e displays a schematic diagram of the data acquisition circuit, which uses two operational amplifiers to extract the signals. The first operational amplifier converts the current signal into a voltage signal. When current flows through \(R_{1}\), a voltage difference is generated across \(R_{1}\). Based on the virtual short principle, there is no current flowing into the input of the operational amplifier, so  
\[(V_{5}-V_{2})/R_{3}=V_{2}/R_{5} \tag{1}\]  
\[(V_{4}-V_{1})/R_{2}=(V_{1}-V_{3})/R_{4} \tag{2}\]  
From the virtual short principle, we can conclude that  
\[V_{1}=V_{2} \tag{3}\]  
Assuming \(R_{2}=R_{3}\) and \(R_{4}=R_{5}\), we can derive the following from the above three equations:  
\[V_{3}=R_{4}(V_{5}-V_{4})/R_{2} \tag{4}\]  
Figure 3: Design and components of the data acquisition circuit.