APPLIED UVc STERILIZATION CHAMBER
MAE 156B | SPRING 2023 | GROUP 25UNIVERSITY OF CALIFORNIA SAN DIEGOBACKGROUND
Shopping carts are known to be one of the highest pathogen transmission vectors identified by Public Health. Bacteria can range from Campylobacter to salmonella and E. coli, which can cause illnesses such as headache, fever, abdominal pain and nausea. The Centers for Disease Control notes that the cold and flu viruses can generally survive on hard surfaces from two to eight hours. Additionally, studies show that the amount of bacteria found on shopping cart surfaces are higher than those found in public bathrooms. However, public bathrooms are regularly cleaned, which is not the case with shopping carts.
OBJECTIVE
Originally, the goal of the project was to design a sterilization chamber for supermarket shopping carts, transport carts, and their suitable cargo. However, the scope of the project had been narrowed to design and test a fixture array configuration which maximizes illumination uniformity and minimizes shadowing, while conforming to kinematic restraints and specifications. The current focus is on the appropriate configuration of lighting. We will consider how to quantitatively assess and test the success of our design. This commercial conveyance device utilizes Ultraviolet light to effectively eliminate bacteria contaminating the surfaces of shopping carts. The original machine can also provide rapid medical-grade sterilization to any suitable solid surface objects sent through its sanitation chamber, for use in medical facilities, laboratories, or any clean-room environment where pathogen control and eradication is a priority.
Our Solution
Performance
The device surpasses the objective of a log 3 pathogen removal. The results (as shown more in depth in the Final Design Page) reveal that a log 4 removal of most small RNA viruses is essentially doubled with average UV-c dosage values being in the range of 64 to 65 mJ/cm^2. The standard evaluation for UV sanitization lamps is 52.6 mJ/cm^2 which has also been surpassed. There are a few spots such as the corners of the inner cart fixture which receive a low dosage in the range of 51-53 mJ/cm^2 but these values are still above the log 4 reduction of small RNA viruses.
The experimental results also validated the simulation results which were performed prior to hardware testing. This reveals that the simulation software with the proper parameters is a useful resource for future teams who may pick up the project and want relatively accurate simulation results before building any sort of new fixtures. For a complete in depth on all the performance analysis it is encouraged to take a look at the Final Report.
An executive summary (2 page extended abtract can be found at the above link).