UV-C Disinfection Pad

Acknowledgements

Project Advisor: Robin Steele

Technical Advisor: Dr. Ata Keyrandish and Dr. Stephen Geer

Donations Made by: Tariq Ahmad and Satview Broadband Ltd

Elevator Pitch

In the US alone, 572,000 lives have been lost due to COVID-19. One valuable lesson learned from this pandemic is the need for reducing bacteria transmission to save lives. Looking at the current situation in hospitals that heavily use masks, disinfection agents, and hand sanitizing stations, it is essential to have effective methods for preventing the spread of germs. However, these practices do not cover the most used and frequently overlooked surface of the hospital, the floors that are walked on. Therefore, Team GrUV came up with a solution that will keep shoes clean as doctors, patients, and visitors use hospital facilities. The introduction of a UV-C disinfection pad serves as a solution that will save lives from healthcare-associated infections.

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Gallery

Design Approach

Design Solution

SolidWorks Load Simulation

The design utilizes UV-C light running at 254 nm wavelength for 10 seconds to allow a safe and consistent method to disinfect a person’s shoes without the risk of exposing the user to a dangerous amount of UV radiation. The pad will be able to withstand a structural load of up to 350 lbs which has been analyzed through SolidWorks simulation (figure on the left).

There will be 8 strips of UV-C LEDs with 6 Lights on each strip. Through running simulations on Matlab to find the cone of effectiveness for the lights allowed the team to deem the proper distance between the lights without losing disinfection power. The team went for a 99.99% disinfection goal with a log 4 reduction of microbes which means the number of germs is 10,000 times fewer. Overall, the system was further validated by FMEA testing, computational 3D plots, and technical advisors.

The final design of the pad allows users to step on the glass surface for about 10 seconds, where activation of a push button will activate the UV-C LEDs to disinfect the outsoles of the shoes. This pad is powered through a wall outlet, through an AC/DC converter, and then through a board with the Arduino Nano wired to a relay activated by the pressure button sensor, and then hooked up to the LEDs. The small electrical components will be hidden inside the pad and safely secured from possible electric shock or water damage. The finished pad has an aluminum casing that is strong enough to hold 350 pounds of structural load and endure long usage. Overall, this design has been thoroughly tested, simulated, and constructed safely to be implemented in hospitals. The final design’s total cost was $2,260.25 while the team was given a budget of $5,000.

To test the disinfection product’s efficacy, the team was able to send off the finished prototype to technical advisor Dr. Ata. With his optics lab, he was able to quantify data about the warm-up time, radiation spectrum, and irradiance distribution for the physical UV-C light pad. The radiation spectrum results showed an intensity peak at the proper 254 nm wavelength and an instantaneous warmup time. The irradiance results showed a sufficiently high output for 4-log disinfection of certain spores, bacteria, viruses, and protozoa. For example, the pad can reduce the number of certain strains of Staphylococcus aureus bacteria, which does not have a developed vaccine and is the cause of serious medical issues like meningitis and sepsis, by a factor of 10,000. This provided evidence that the pad reaches the necessary levels of disinfection. The table below shows the log reduction of a certain selection of microbes achieved by the pad.

Throughout the design process, the team encountered challenges that they needed to solve for the project to succeed. For example, in the preliminary phases, the team’s initial design was a metal grate that allowed UV light to shine through with minimal obstruction. However, the team realized that the grate could pose an issue for debris falling through and the cleanliness of the top of the surface. The team urgently switched to using a transparent fused quartz surface to ensure the UV-C light cleans the top of the surface each time used. The fused quartz was difficult to obtain, but the client had a supplier who was willing to send us sheets of it.

Another challenge the team faced was the AC/DC converter. The original converter the team ordered allowed voltage from a wall outlet to be converted to 12 V, which was necessary for the converter to power the Arduino and other components. However, when implemented, it was not making the minimum 10% power load that allowed the relay to work properly. The team had to create a circuit with about 10 power resistors to reach at least 48 Ω of resistance. Although this method worked, it was easier to order a new converter to eliminate the load issue.

A constant challenge that the team faced was project management. In the second semester, the team began to fall behind due to supplies not coming in. The team relied more on the Gantt chart to get a broad overview of the project rather than short tasks in Trello. The team designated weeks of time to predict time-consuming tasks. Meanwhile, the team was proactive about other action items that could be completed before the materials arrived.

Then the COVID-19 situation posed an issue when trying to properly design for the needs of a hospital. The team wasn’t able to tour the layout of a local hospital, so they had to switch gears to find user-end feedback. Emails with local hospital workers and management helped the team realize that the pad needed to withstand lots of use and be powered through a nearby power supply. This eliminated concerns about portability, size, and durability. The team was able to work through this challenge by making appropriate design decisions based on stakeholder feedback and research.

Next Steps

The team was able to create a functioning prototype of a UV-C disinfection pad. However, just like any other project, there are a variety of ways to improve, decrease cost and optimize the solution. The main next steps goals involve creating a production plan for the team’s client to minimize cost and make the implementation of this product as effortless as possible. For this to happen our client proposed injection molding of the housing components, as this will be lighter, cheaper, and faster to produce in large quantities.  

In the end, the final cost of the aluminum-based UV-C pad was $3,145.67. In order to determine a way that would lower the overall cost of the pad, the team looked into getting quotes for injection molding to determine what the projected cost would be if that was the method of production. After receiving a quote for 1000 pads, it was calculated that one pad would cost approximately $1,626.94. This would decrease the cost of our pad by roughly 50%. One thing to note is that the cost of the pad will continuously decrease if the number of pads that are being built increases with order purchase.

It is important to note that with any design change there comes pros and cons however with enough pads produced there is a significant price reduction, so savings on cost and an overall weight reduction allowing the pad to be moved more easily. 

Meet the Team