Liquid Crystal COVID-19 Test Would Be Fast, Cheap and Accurate

How many times have you stared at a home COVID-19 test, waiting for the faint line that confirms an infection? Those home antigen tests often fail to detect a recent infection or one with no symptoms. A PCR test is more accurate, but it must be done by a medical lab, and the results take days to deliver. 

New research from the U of A could lead to an inexpensive, at-home COVID-19 test that uses liquid crystals to deliver results in less than two minutes. The technology can accurately detect trace amounts of SARS-CoV-2, the virus that causes COVID-19, so that early and asymptomatic cases will be detected. 

The research was published in the journal Advanced Materials Technologies. The corresponding authors are Karthik Nayani, assistant professor of chemical engineering, and Homa Ghaiedi, a U of A doctoral candidate when the research was conducted who now works in industry. 

Liquid crystals are rod-shaped molecules that align themselves in the same orientation. In an LCD television or display, an electric voltage changes the orientation, blocking or letting light pass through like blinds on a window. 

For the COVID test, the reorientation of the rods is triggered when SARS-CoV-2's spike protein binds with a metallic surface. In the body, coronaviruses use their protruding spike proteins to infect healthy cells. 

The sensor could detect the presence of the coronavirus in a liquid with a concentration of 2,000 spike proteins per milliliter, far below the typical 10,000 to 100,000,000 per milliliter concentration of the virus in the saliva of an infected person. 

The rearrangement of the liquid crystals is very sensitive to orientation at surfaces. When a few rod-like molecules at the surface turn, the others in the bulk of the fluid follow, like a squadron of soldiers following their sergeant. In the COVID test, the spike protein binding with the surface will set off a chain reaction, flipping the orientation of enough liquid crystal molecules so the results can be viewed by the naked eye. 

"That's the beauty of liquid crystals," Nayani said. "You can capture these events on the surface and transmit them over much larger length-scales." 

The liquid crystal sensor could also identify pathogens that are unknown today, making it ready to deploy if the mutation of a virus leads to another pandemic. 

The same liquid crystal technology could also detect dangers like formaldehyde or hydrogen sulfide. In a battle, it could warn of chemical weapons and nerve agents. On a farm, it could confirm the presence of pesticides. 

"The dream here is airborne detection. Now we're not even talking about it getting into our body," Nayani said.