## 3 Results and Discussion
### Prototypes' Effectiveness in Reducing a Phone's Magnetic Field
Figure 20: Experiment with measuring phone radiation when the phone is used with RD1 to RD4. The results of the Prototype 1 cover (Table 4) and Prototype 3 cover (Table 6) show that distances of 10 mm, 15 mm, and 20 mm away from the phone during in-app phone conversations can effectively reduce phone radiation to 0 uT. It can be concluded that the minimum distance away from the phone is 10 mm, and both Prototype 1 (10 mm cover) and Prototype 3 (10 mm cover) are effective in preventing phone radiation during phone conversations. The results of using the Prototype 2 case (Table 5) and Prototype 3 case (Table 7) show that phone radiation is negatively related to distance away from the phone. The thicker the phone case is, the less phone radiation is measured. Both results show that the highest phone radiation is measured when using a 5 mm thick phone case. The phone radiation measured gradually decreases when using a 10 mm thick phone case and a 15 mm thick phone case. The phone radiation reaches its lowest when a 20 mm thick phone case is used. In conclusion, in order to prevent 90% of phone radiation during phone standby when Wi-Fi, data, GPS, Bluetooth, and Hotspot are on, the minimum thickness of the phone case should be 10 mm. Using the 10 mm thick Prototype 2 and 10 mm thick Prototype 3 can both effectively prevent 91% and 90% of phone radiation, respectively. Both the Prototype 2 case and Prototype 3 case are made of the same material and thickness with the same experiment setting, but we can see the discrepancy of phone radiation measured between the 5 mm thick Prototype 2 case and Prototype 3 case is the highest. This is due to the magnetic field measured fluctuating over time. With the higher level of magnetic field at a distance of 5 mm away from the phone, the higher the standard deviation is and, as a consequence, the higher the discrepancy in phone radiation. The discrepancy of phone radiation measured between the 10 mm thick Prototype 2 case and Prototype 3 case is gradually reduced to 0.1 uT. This is because the level of the magnetic field at a distance of 10 mm away from the phone decreases and, as a consequence, the smaller the discrepancy in phone radiation. The discrepancy in phone radiation measured between 15 mm and 20 mm thick Prototype 2 case and Prototype 3 case becomes 0 uT. The reason is that the level of the magnetic field at distances of 15 mm and 20 mm away from a phone is low or close to negligible, and there is no discrepancy in phone radiation as a consequence. Regarding Prototype 1, the purpose of it is to reduce the potential impact of phone radiation on the brain. The result in Table 4 shows that using Prototype 1 with a 10 mm cover, 15 mm cover, and 20 mm cover during an in-app phone conversation can effectively reduce phone radiation by 100%. Since the minimum preventive distance away from the phone is 10 mm, considering the factor of user-friendliness with less weight and smaller in size, Prototype 1 with a 10 mm cover is optimal and preferable. Regarding Prototype 2, if the goal is to prevent at least 90% phone radiation while the phone is on standby in the user's trousers pocket, considering the factor of user-friendliness with less weight and smaller in size, a 10 mm thick Prototype 2 case is optimal and preferable. Considering that the users are super concerned about the prevention of phone radiation and the goal is to prevent as much radiation as possible, a 20 mm thick Prototype 2 is preferable. Regarding Prototype 3's cover part, since the purpose of it is to reduce the potential impact of phone radiation on the brain, the result in Table 6 shows that using Prototype 3 with a 10 mm cover, 15 mm cover, and 20 mm cover during in-app phone conversations can effectively reduce the phone radiation by 100%. Since the minimum preventive distance away from