When plasma equipment manufacturer PVA TePla America was asked by a manufacturer of real-time PCR diagnostic tests, to treat hundreds of thousands of plastic cartridges used to test for COVID-19, they immediately jumped at the task.
Plasma is a state of matter, like a solid, liquid or gas. When enough energy is added to a gas it becomes ionized into a plasma state. The collective properties of these active ingredients can be controlled to clean, activate, chemically graft and deposit a wide range of chemistries.
In this case, plasma treatments play a small but critical role by modifying the surface of the plastic multi-well cartridges used in real-time polymerase chain reaction (PCR) tests.
Untreated synthetic polymers used to make multi-well plates and cartridges are naturally hydrophobic (repel water) and so provide inadequate binding sites for cells to anchor effectively to their surfaces. To improve biomolecule attachment, survivability and proliferation, they must be surface modified using plasma to become more hydrophilic.
Plasma treatments also help eliminate air bubbles that can accumulate at the edges of the well bottom, which can interfere with the proper mixing of reagents and also limiting the available surface area. Depending on the assay, this can dramatically impact the quality and resolution of the test.
With COVID-19, there was also a need to detect the presence of the virus at its earliest stages, which meant fewer diagnostic markers would be available – another factor that can impact the quality of the test results. This was yet another reason that plasma treatment was so important.
As a manufacturer of plasma equipment, PVA TePla also offers contract processing services. As such, the company already had a relationship with the manufacturer, treating similar style cartridges. However, with a global pandemic at hand, the challenge was not only to treat the multi-well cartridges, but also to fast-track the process to assist the company in its quest to produce millions of tests as rapidly as possible.
“We were treating approximately 1,500 test cartridge units for the customer and now they were asking us to process more than 50,000 cartridges per month. Since the cartridge had many wells, that equates to roughly 500,000 individual tests that could be conducted each month,” says Michael Barden, head of research and development at PVA TePla.
To speed the process, PVA TePla worked with its customer to optimize the plasma processing time from an hour per batch to only 10 minutes. This significantly increased throughput and allowed for “just-in-time” delivery of processed parts.
Through its continued work and development activities PVA TePla has developed advanced plasma techniques for surface activation to create long lifetime, hydrophilic surfaces that also prevent any problematic air bubbles from forming which can negate accurate testing results.
Although each batch could be processed in under five minutes, Barden says there were other ways to optimize the throughput, however. In the past, incoming parts were shipped with the components loose in bags. Given that the quantities would now be in the tens of thousands per month, sorting, preparing and counting added significantly to the time and costs of processing. PVA TePla staff had to handle each of the items by hand, which was not ideal.
Another issue recognized over time was that hard polymer parts can scratch or scuff other items, particularly when loosely packaged in bags, causing a yield reduction as some cartridges had to be rejected given that even fine scratches could impact the final testing results.
After reviewing in detail the upstream and downstream processes with the manufacturer, it was determined that upon receipt of the processed parts from PVA TePla the customer would then package the cartridges in PETG trays, Barden suggested that the company instead ship the parts already in those trays.
“We already had experience processing items in PETG trays and with some minor adjustments to hardware and the plasma process parameters it was possible to achieve the desired result of treating just the exposed wells, not the outside of the cartridge,” explains Barden.
The customer then designed the PETG trays to hold a defined number of cartridges and optimize the quantity of parts contained in a shipping box allowing for a reduction in shipping costs. PVA TePla was able to optimize the number of trays which could be readily placed into its own fixturing device when plasma treating each batch.
This also eliminated any need to handle the cartridges, which are loaded using pick-and-place robots into the PETG trays. Once at PVA TePla the trays are loaded, the parts treated, removed and then forwarded to the next step in the production at another facility.
In addition to speed the process modifications allowed the manufacturer to reduce the overall cost-per-part and improve their profit margin.
According to Barden, the customer aims to keep raising production capacity.
“During a pandemic, you have to do all of this much faster and you need your supply chain to be just-in-time,” explains Barden. “So, you must work hard to streamline all elements of product manufacturing and we work with all of our customers to do that. Now, production of 25,000 to 50,000 surface-treated cartridges is possible in just a few days.”