# Rapid and Cost-Effective Fabrication and Performance Evaluation of Force-Sensing Resistor Sensors
## 1 Introduction  
Force measurement is essential for numerous applications, including industrial automation, robotics, consumer electronics, and medical devices [1, 2, 3, 4]. Accurate and reliable force sensors are vital for tasks such as load monitoring, robotic gripping, tactile feedback in touchscreens, and patient monitoring systems. Among the available force sensor technologies, force-sensing resistors (FSRs) have gained significant attention due to their thin profiles, flexibility, and cost-effectiveness [5, 6, 7]. FSR sensors operate on the principle that electrical resistance decreases as applied force increases, making them suitable for both static and dynamic force measurements [8, 9, 10, 11]. Typically, an FSR sensor consists of a conductive polymer that alters its resistance in response to applied force, with a compact form factor often less than 0.5 mm in thickness, enabling integration into space-constrained devices such as wearable electronics and portable medical devices. Commercially available FSR sensors, like those from Interlink Electronics (Camarillo, CA, USA) (e.g., FSR-402) and Tekscan (Boston, MA, USA) (e.g., FlexiForce A201), are widely used as benchmarks for evaluating alternative fabrication methods [8, 9, 11]. These sensors are employed in various applications, including robotics, musical instruments, and sports equipment, due to their robustness and ease of integration. However, their cost can be prohibitive for large-scale deployment or cost-sensitive projects. The growing demand for cost-effective, flexible, and high-performance force sensors has led researchers to explore new materials and fabrication methods. Pencil graphite has emerged as a promising material due to its cost-effectiveness, accessibility, and excellent electrochemical properties, offering a potential solution to the limitations of conventional force sensors [12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25]. For instance, paper, with its durable and flexible mechanical properties, has been identified as an ideal substrate for FSR sensors [26; 27; 28; 29; 30; 31]. Numerous studies have investigated the potential of pencil graphite in sensor applications. [PERSON] et al. [12] focused on surface activation techniques to enhance sensor performance, particularly for dopamine detection. [PERSON] et al. [13] demonstrated a simple, cost-effective method for fabricating strain sensors, highlighting the feasibility of pencil graphite for sensor construction. [PERSON] et al. [14] showcased the high sensitivity and flexibility of pencil graphite sensors in wearable applications, while [PERSON] et al. [15] explored their use in structural health monitoring. [PERSON] et al. [16] developed an integrated sensing platform with power and read-out, providing a low-cost solution for electrochemical sensing. [PERSON] et al. [17] and [PERSON] et al. [18] examined the use of graphite pencil traces in humidity sensors, emphasizing their cost-effectiveness, simplicity, and environmental benefits, with attention to how stroke count and pencil grade affect sensitivity and response time. [PERSON] et al. [19] discussed pressure sensors that detect pressure through changes in contact resistance in graphite layers, demonstrating high sensitivity and fast response times, especially in wearable devices. [PERSON] et al. [20] utilized pencil graphite electrodes for electrochemical analysis, detecting substances like drugs and heavy metals. [PERSON] et al. [21] detailed pencil graphite-based gas sensors that alter electrical properties when interacting with specific gases, such as NO\({}_{2}\), using a graphite pattern on silver interdigitated electrodes. [PERSON] et al. [22] presented pencil graphite-based on-skin electronics for biosignal detection in wearable health monitoring devices, emphasizing their low cost and environmental friendliness. [PERSON] et al., [PERSON] et al., and [PERSON] et al.