- Week 6 -
Last Week
The team was split into two groups. Stafford, Alex and Luke worked on designing the UV emitter design. The second group consisted of Robert, Dylan, Michael and Seth who worked on designing a case that will house the UV light.For the case design, Each member split into looking into different parts of the case.
Robert was tasked with the interior of the system
Michael and Dylan with the exterior of the case
Seth with the case that will protect the entire system for transport.
This Week
After getting our own seperate tasks, we all found materials that would be suitable for our PDS requirements.
Robert has found a material called polyimide that satisfy the PDS for being light-weight, compression loading and blocks UV light from escaping the closed space, protecting the user. An alternative was suggested by Michael to use polycarbonate which is lighter and reflects the UV light allowing for greater exposure for the mask but a drawback is the compression strength is less than the polyimide. This would require us to do further analysis which will be done eithier through hand calculations or SolidWorks to see which material or a combination of both will satisfy the PDS.
Michael has looked into different materials that can be use for the exterior of the system, After research, Michael concluded that the best material would be wooden material instead of a metal design. That is because it satisfy the PDS for being light-weight and durable. So far the materials Michael has chosen is either mahogany or oak. Michaels next steps are to model the exterior and calculate the stresses on the system.
Dylan focused on the base of the system. Since our artifact is realitively small and will be placed on countertops and tables, we need to make sure that this device can stay in place even if a force such as a bump is applied. Dylan will be looking into a rubber material that can offer enough friction that can prevent it from sliding. Dylan's next step is to calculate the forces on the system and see if the system will move or not.
Seth has looked into materials that are used into phone cases to test whether or not if they can be used in the same application for our device. The case will be used to protect the system. The case will be used more to satisfy the durability of the system, making sure it can withstand heavy impact and a long fatigue life, surviving multiple drops during its lifespan. Further fatigue-life testing will need to be conducted.
Dylan focused on the base of the system. Since our artifact is realitively small and will be placed on countertops and tables, we need to make sure that this device can stay in place even if a force such as a bump is applied. Dylan will be looking into a rubber material that can offer enough friction that can prevent it from sliding. Dylan's next step is to calculate the forces on the system and see if the system will move or not.
Seth has looked into materials that are used into phone cases to test whether or not if they can be used in the same application for our device. The case will be used to protect the system. The case will be used more to satisfy the durability of the system, making sure it can withstand heavy impact and a long fatigue life, surviving multiple drops during its lifespan. Further fatigue-life testing will need to be conducted.
Figure 1: The interior design of the system, can store about 8 to 9 masks. The hole for the motor needs to be shifted upwards to fit the motor in the system.
Figure 2: Sketch of how the arm will rotate around the mask.
Figure 3: SolidWorks model of the emitter arm.
We have determined that the most efficient UVc LED to use is made by SeoulVioSYS and offers 60mw of radiant flux at the emitter. The LED can be seen in Figure 4.
Figure 4: SeoulVioSYS's Deep UV LED - 275nm (CUD8AF4D)
Using the inverse square law of radiant flux over distance from the emitters. We calculated that there are the decontamination time is excellent for a short distance of 1-2cm. However there is a severe drop-off in the level of irradiance as the distance increases. Figure 5 shows the time required to reach a dosage of 1J/cm^2 as the distance increases. This is a problem because our present design of the rotating emitter arm requires the light to travel approximately 12cm to reach the inside (user side) of the mask. Even with using an array of 30 LEDs, at this 12cm of distance it would take 16.75 minutes to decontaminate the surface. The calculations used for Figure 3 were assuming stead-state exposure and were done before considering the exposure frequency related to the rotating of the emitter arm.
Figure 5: The time required to reach the minimum dosage to decontaminate the masks (1J/cm^2) as compared to the distance from the emitters. The orange line is the desired decontamination time of 30 seconds.
Next Week
We will be analyzing the stress of the system, completing the strength aspect of the PDS and will finsih the sketch work in SolidWorks or other CAD systems. We will also be searching for an alternate UVc Emitter Array option that will allow us to meet our design needs. We will begin preparing for the CDR presentation that will happen next week.