# Rapid and Cost-Effective Fabrication and Performance Evaluation of Force-Sensing Resistor Sensors
## 2 Experimental Method
### Fabrication of the FSR Sensor  
The assembly of the FSR sensor involves layering the prepared FSR sheets with conductive electrodes and securing them to form a functional sensor. The FSR sensor was fabricated using the same structural design of commercial products, as depicted in Figure 2. A double-sided tape with a thickness of 0.1 mm was applied as a spacer, positioning the electrode outside the conductive sheet and connecting the conductive side to the 0.25 mm wrapping, while the outer copper sheet electrode was grounded. This setup ensures proper grounding. The FSR sensor operates by allowing current to flow when force is applied. As shown in Figure 2, the top and bottom layers of the piezoresistive material are separated by a gap of approximately 0.1 mm, maintained by double-sided tape on either side. When force is applied to the upper electrode plate, the top layer bends and contacts the bottom  
Figure 1: FSR sensing sheet. **(a)** Velostat-1361, **(b,c)** 4B Pencil lead on a copy paper, **(d,e)** 9B pencil lead on a copy paper, **(f)** TE piezoelectricity sheet, **(g,h)** mixture of 9B pencil lead powder and silicone sealant on a copy paper.  
layer, resulting in a change in resistance proportional to the contact area, thereby enabling current flow. This process is illustrated in Figure 3.  
Step-by-Step Assembly (1) Electrode attachment; Description: Copper foil (Cu foil) was attached to the back of each FSR sheet to serve as the electrode. Procedure: The Cu foil was adhered to the FSR sheet using conductive adhesive (Figure 3a). (2) Wire connection; Description: Wrapping wire (0.25 mm) was connected to the Cu foil and the FSR force surface to ensure electrical conductivity. Procedure: The wire was securely attached to the Cu foil (Figure 3b). (3) Covering and securing; Description: The Cu foil and wire assembly were covered and secured to the FSR sensor to ensure stability. Procedure: The covering process involved adhering the Cu foil and wire assembly as shown in Figure 3c. (4) Opposite side assembly; Description: The opposite side of the FSR sheet was assembled similarly, with the Cu foil and wire assembly. Procedure: The same steps were followed to prepare the opposite side of the sensor (Figure 3d). (5) Double-sided tape application; Description: Double-sided tape served as a spacer between the two FSR sheets. Procedure: The double-sided tape was adhered to one FSR sheet, and the protective paper was peeled off to expose the adhesive (Figure 3e). (6) Final Assembly; Description: The prepared opposite side was attached to the exposed adhesive side of the double-sided tape, completing the sensor assembly. Procedure: The final step involved carefully aligning and attaching the two FSR sheets (Figure 3f).  
Figure 3: Fabrication of the FSR sensor. (**a**) Cu foil electrode, (**b**) wire on electrode, (**c**) wrapping wire, (**d**,**e**) cover, (**f**) taping, and (**g**) final FSR sensor.  
Figure 2: FSR sensor structure.  
By following these steps, a cost-effective and functional FSR sensor was successfully fabricated. The next sections will discuss the testing and performance evaluation of these hand-made sensors compared to commercial alternatives.