‘SARS-CoV- 2′, the name is sufficient to create a fear in human mind. This disease isn’t only creating life threats to elderly people, it’s affecting the economy worldwide as countries have implemented the lockdown to prevent it!! Researchers specially Biologists are trying their best to find a vaccine.
Since the vaccine for ‘SARS-CoV-2′ is not yet found, the best ways to slow the spread of virus are the ‘Early Detection’ and ‘Sterilization of Contaminated Surfaces’ and here Physics, specially ‘Optics & Photonics’ is leading the fight.
Safer Screening :-
Measuring body temperature is the widely used as the preliminary screen and due to the contagious nature of the virus, remote, non-contact options are being used. Optics has provided various technologies for measurement of internal body temperatures remotely. We can determine the temperature of any object by determining the amount of infrared energy emitted by it, provided its emissivity is known. The infrared radiation emitted by the human body has a peak around 9µm wavelength. Variations in body temperature cause changes in emitted IR radiation, thus allowing thermal imaging systems to identify if the body temperature is not in normal range. Now many physicians are using these infrared-based thermometers for measuring thermometers. Infrared imaging cameras can simultaneously image and measure the temperature of a large group with significant safety. Usually the latter process of screening can be followed in airports.
Fig 1:- Thermal Imaging of Human Body (Source:- Edmund Optics)
These IR imaging thermometers usually use semiconductor diode detectors which are sensitive in the far-infrared spectral region (8 to 14 µm ).
Fig 2:- Transmission ranges for IR substartes
Obviously, fever detection doesn’t confirm the presence of ‘SARS-CoV-2′ in human body but it can identify the inviduals who must proceed with the virus testing.
If a patient shows the symptoms of ‘SARS-CoV-2′, we’ve to proceed with the molecular diagnosis test. This diagnosis is based on a technique known as ‘real-time reverse transcription polymerase chain reaction (RT-PCR)’. In this process the small amount of viral genetic material collected from patient’s nasal or throat swab is amplified and tested and here optics takes an essential role.
Many PCR screening systems rely on fluorescence. here targeted viral genetic molecules (DNA or RNA) are tagged with accompanied quencher and fluorescent dyes that emit light when exposed to a shorter wavelength input. With each round of amplification, the fluorescent molecules are released into the buffer solution and gets separated from the quencher. That’s how the amplification of DNA or RNA occurs and it’s detected via fluorescence in real time.
Fig 3&4:- RT- PCR working principle & Capheid Doctor’s office RT-PCR instrument (Source:- Capheid)
The RT-PCR device follows the same working principle as fluorescence microscope. ‘An excitation filter allows wavelengths from the illumination source that would excite the fluorescent sample to pass. These excitation wavelengths reflect off a dichroic filter and are focused onto the sample by lenses. Fluorescent emission from the sample transmits through the dichroic filter towards lenses that focus the light onto the system’s detectors. Measuring the amount of fluorescence lets the PCR screening system determine the presence of molecules that would indicate if a sample is SARS-CoV-2 positive’.
Fig 5:- Schematic of RT-PCR instruments (Source:- Edmund Optics)
This RT-PCR uses Laser Diodes or LEDs as excitation and Semiconductor diodes or photomultiplier tubes for detection. These instruments can typically process 96 or 384 samples in less than one hour. Currently the false negative test is almost 30% and that’s why repeated testing is required for the precise result.
Optics is also emerging as an essential weapon for ‘Sterilization of Contaminated Surfaces’. Usually viruses and bacteria are very sensitive to UV light. Specially lights in UV-C region (200-280 nm) mutates the RNA of Virus which is essential for ‘Viral Replication’.
Fig 6:- Prototype of an LED sterilization system being tested by Bolb Inc.
[Image: Bolb Inc.]
Arrays of UV LEDs can generate high UV power levels which decontaminates certain surfaces more efficiently than many chemical reagents. Recently it has been found that about 1 min exposure time is sufficient to kill bacteria and viruses if we use 1-W- average power UV-LEDs located about 1m above the contaminated surfaces. Further testing on the effectiveness of UV-LEDs to kill ‘SARS-CoV-2’ virus on the surfaces is in progress.
Though researchers in these fields of physics are not directly connected with the search for vaccine of ‘SARS-CoV-2’ , they are helping medical professionals to fight against ‘SARS-CoV-2′ efficiently with their research outcomes.
PhD Scholar (P.I. Prof. Alexei Sokolov)
Department of Physics and Astronomy
Texas A&M University
About the author: Hi, I’m Dipankar Sen, an early-career researcher. I received MS in Physics from IISER Bhopal in 2019 and came to USA for higher studies. Currently I’m pursuing my PhD in Department of Physics and Astronomy, Texas A&M University under Prof. Alexei Sokolov. I’m also affiliated with Institute for Quantum Science and Engineering’s (IQSE), Texas A&M University. My research interests are Ultrafast Laser Physics, Nonlinear Optics and Material Sciences. Currently I’m working as a full time Graduate Teaching Assistant for Department of Physics & Astronomy, Texas A& M University.