How is MEMS involved in coronavirus testing?

Testing for the presence or absence of coronavirus (COVID-19) is one of the major issues during the current pandemic.

On March 21, 2020, Cepheid, a company that designs and manufacturers molecular testing systems and products announced that it received Emergency Use Authorization (EUA) from the U.S. Food & Drug Administration (FDA) for its Xpert Xpress SARS-CoV-2 test system. The rapid molecular diagnostic test provides qualitative detection of SARS-CoV-2, the virus causing COVID-19. Designed to operate on any of the company’s more than 23,000 automated GeneXpert Systems worldwide, nearly 5,000 of these systems are in the US for point-of-care testing and in-hospital usage.

To determine whether or not a patient has the virus, a nasal sample is taken using a swab, mixed in a tube with a liquid so the sample can be dispensed with a pipette into the test cartridge that includes the testing reagent. Test results are available in about 45 minutes. In addition to configurations that can test one, two, four, 16 or 48 modules, the largest system can handle up to 80 cartridges at a time for automated, simultaneous processing.

According to AMFitzgerald & Associates’ March 2020 Newsletter, this process uses microfluidic chip-based polymerase chain reaction (PCR) analysis machines. A simple two-step description of the PCR process is:

1. thermal cycling amplifies the DNA present in a patient’s swab sample, and
2. then fluorescence optical detection searches for the virus’s specific DNA

Unlike a traditional PCR machine that would take many hours to thermal cycle and reach a result, the small size of the microelectromechanical systems (MEMS)-scale heaters and reaction chambers provide a significantly faster heat-cool cycle and results in minutes.

Cepheid tests will begin shipping the week of March 23.