Background
Fig. 1: An illustration of the Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2), from the Centers of Disease Control and Prevention.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), commonly synonymous with the disease it causes, COVID-19, is a virus that rapidly spread across the world in 2020 and remains an ongoing global health concern. The Expedited COVID Identification Environment (EXCITE) Lab, at the University of California San Diego, performs testing for students and faculty at the university as an integral part of the UC San Diego Return to Learn Initiative. This project is aimed at streamlining the testing process done at the EXCITE Lab in order to increase the throughput of daily COVID-19 tests.
The original throughput of COVID-19 tests from the EXCITE Lab is approximately 1,000 samples per day. However, the lab's goal is to have a sampling throughput of approximately 10,000 samples per day. Our goal was to help the EXCITE Lab work towards achieving this throughput by focusing on improving the decapping process of the sample tubes in the workflow.
The Obstacles
The main obstacles were as follows:
The original workflow utilized 5 mL tubes since there were issues with the swab being too large for smaller tubes.
The EXCITE Lab has a machine that can automatically decap 5 mL tubes 48 at a time, however, due to supply chain issues this brand of tube was not available at the scale needed at the EXCITE Lab.
An ideal solution would be to use tubes that have the diameter of 1 mL tubes, since the EXCITE Lab has a machine that can decap this size of tube 96 at a time. However, there is still the problem that the 1 mL tubes that can be decapped with this machine is too short for the swabs used for testing.
If this solution was pursued, we would need to find a way to mitigate the swab issue. This entailed using a different type of tube, which meant that the decapping machine would need to be modified to support a different brand of tube.
Once we determined what the main issues and goals were, we decided to focus on two decapping processes: one for the 5 mL workflow (which was the original workflow) and another for the 1 mL workflow (which would be the ideal solution).
Objective
The overarching objective of our project was as follows: increase the daily throughput of COVID-19 tests. We approached this goal by focusing on two areas of the workflow:
Efficiently removing the caps from the currently used 5 mL test tubes.
Incorporating the lab's decapping machines that are currently not in use. Specifically, the Capit-All machine that could decap 96 tubes at a time.
Two Workflows
Fig. 2: The two workflows in the EXCITE Lab. The top workflow (in blue) handles 5 mL tubes, which is the original workflow used in the EXCITE Lab. The bottom workflow (in red) is the ideal workflow, which would require 1 - 1.4 mL tubes in order to operate. The focus of this project is in the decapping portion of the workflow, shown within the dashed lines.
Key Components in Each Workflow
Original: 5 mL Tubes
Fig. 3: 5 mL tube and swab.
Originally used 5 mL tube with a swab.
Fig. 4: Linear rack that holds 32 tubes.
Tubes are placed in a linear rack and decapped.
Fig. 5: Hand drill that unscrews 5 mL tube caps.
The 32 tubes in the rack are individually decapped manually with a hand drill.
Fig. 6: The Hamilton machine, used for 5 mL tubes.
Tubes go in to the Hamilton, where samples are collected and placed in a 96-well plate.
Ideal: 1 mL Tubes
Fig. 7: 1 mL tube and swab.
1 mL Tube with swab.
Fig. 8: A 96-well rack for 1 and 1.4 mL tubes.
Tubes are placed in a 96-well rack.
Fig. 9: The Capit-All machine.
The rack is placed in the Capit-All, whcih automatically decaps the 1 mL tubes.
Fig. 10: The Bravo machine.
The Bravo compresses the samples to a 384-well plate and preps the samples for testing.
Final Designs
Fig. 11: An exploded view of a row of Capit-All adapters with respect to the Capit-All prongs, tubes, rack, and stand. The green pieces are the adapters.
Capit-All Adapter - 1mL
This solution is a Flat-Head Adaptor, which is inserted into the prongs of the Capit-All. The adaptor is held in place with an adhesive tape. As the Capit-All descends towards the tube caps, the prongs are rotating, which allows the adaptors to catch onto the grooves of the caps. Since the adaptors are firmly pressed into the caps, friction keeps the caps attached to the adaptors. This allows the caps to be lifted off the tubes once the machine has finished decapping.
Fig. 12: The Parallel Beam Decapper. The blue indicates the acrylic pieces, the black pieces are the linear actuators, and the orange shows the carriages.
Parallel Beam Decapper - 5mL
This solution utilizes the anti-parallel motion of two beams (indicated in blue) to twist the caps off of a rack of 32 tubes. The black Neoprene rubber provides the necessary grip on the tube caps, and the linear actuators (shown in black) provide the sliding forces needed to twist the caps. Hinging arms also allow for some customization for different tube caps - one arm can be easily adjusted to account for slightly smaller or larger diameter caps.
Capit-All Adapter
(1-1.4 mL Workflow)
Fig. 13: A CAD of the final Capit-All Adapter in the Capit-All prongs.
Fig. 14: A prototype of the Capit-All Adapter. This model does not have the same taper at the top, however, the bottom half (area that interacts with the tube caps) is the same shape as the final design shown in Fig. 13.
Decaprecap Micronic.mp4Video 1: A video showing the decapping and recapping of test tubes using the Capit-All Adapters. The adapters were individually placed in the Capit-All prongs and held in place with double-sided tape. Here, 95 out of the 96 tubes are successfully decapped and recapped.
Parallel Beam Decapper
(5 mL Workflow)
Fig. 15: The Parallel Beam Decapper prototype standing alone.
Fig. 16: The Parallel Beam Decapper placed around the clamp, which is holding a rack of 32 tubes.
FinalDecapperTest.MOVVideo 2: A video of the Parallel Beam Decapper attempting to decap a rack of 32 tubes. In this video, 11 tubes are successfully decapped. Generally, approximately 1/3 of the tubes were successfully decapped.
Final Design CAD Models
Fig. 17: Capit-All Adaptor.
Fig. 18: Parallel Beam Decapper.
Performance Results Summary
Capit-All Adapter
(1-1.4 mL Workflow)
Fig. 19: The Capit-All Adapter successfully decapping 95 out of 96 tubes.
The latest testing was able to show the adapters decapping and recapping 95 out of 96 Micronic 1.4mL tubes successfully but was able to complete all 96 Matrix tubes consistently. The less successful attempt with the Micronic 1.4mL tubes is suspected to have been the result of manufacturing defects in the cap and the adapter due to the fact that there was only 1 rack of 96 Micronic 1.4mL tubes available at the time of testing. This meant that the caps had to be reused more than once, causing the caps to deform over multiple tests. In practice, this should not be a problem because the tubes/caps will be used only once to avoid cross-contamination. The final prototype was not manufactured in time to test but the only modification was to the adapter-Capit-All interface, not to the adapter-cap interface. As a result, the final prototype should be able to decap and recap all of the Matrix and Micronic 1.4mL tubes without any issues.
Parallel Beam Decapper
(5 mL Workflow)
Fig. 20: A rack of tubes that the Parallel Beam Decapper attempted to decap. Generally, about 1/3 of the caps were successfully decapped with this prototype.
Ultimately, the final Parallel Beam Decapper design was capable of consistently decapping about 1/3 of the tubes in the linear rack. It was apparent from multiple trials that the location of the decapped tubes stayed consistent and corresponded to the placement of the spacers needed to mount the acrylic beam. This was expected since the placement of the spacers directly corresponded to where the noraml force was applied to the acrylic. We believe that this design would be a feasible option for future use if additional spacers were placed along the acrylic beam to evenly distribute the normal force across the beam, and as a result, across the tube caps.
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