Rotationally Symmetric Nanowire Array-based Virus Detection: Single or Multiple Arrays?

In this work we compare the prospect of detecting virus-like particles using single and multiple arrays of rotationally symmetric array of silicon nanowires. Taking the dimension and geometry of the Coronavirus as a reference, resonant wavelength shift and quality factor change of the whispering gallery mode of the nanowire array in the presence of one and two viruses are evaluated employing finite difference time domain analysis technique. For a single coronavirus having protein spike, the maximum shift of resonant wavelength is found to be about 5 nm, whereas for two viruses the shift can be as high as 9 nm. However, interestingly, for two viruses the shift appear to change periodically depending on relative location of the virus particles. As far as multiple arrays for virus detection is concerned, the quality factor of the most strongly confined whispering gallery mode appears to have been reduced by 50% or more because of mode-leakage resulting from coupling between the nanowire arrays. Such weaker confinement of the optical field though may have a diminishing effect on the signal to noise ratio during practical measurements, the detection sensitivity appears to have improved significantly because of the sustenance of whispering gallery resonant modes in the adjacent nanowire arrays.