Theoretical Optimization of Microdisk Sensors Based on Modified Potential for Ultralow-Limit Detection of COVID-19 Biomarker

The novel coronavirus (COVID-19) pandemic has enormous economic and social impacts on global healthcare systems. Therefore, sensitive and reliable detection methods of coronavirus would be in great demand to relieve COVID-led sufferings. Due to the exceptional sensing performances, whispering gallery mode (WGM) resonators have become ideal candidates for biochemical sensing applications. In this article, aiming to achieve ultralow-limit detection of COVID-19, we propose an optimization approach for performance improvement of microdisk sensors based on modified potential. Compared with the conventional eigenequation method based on Bessel functions, the proposed quantum-potential-based approach offers a more efficient way to characterize WGMs based on the potential evolution. The sensing performances such as quality factor, sensitivity, and limit of detection (LOD) have been investigated for microdisk sensors with different radii, resonance modes, and medium materials, resulting in a minimized LOD of 13.321 fM for human monoclonal IgG using a silica microdisk resonator of 110-<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>m radius. Further studies indicate that the selection of cavity medium material would be a specific issue need to be considered to balance the opposite trends of LOD and cavity size for the optimization of sensing performance and integration level in practical use. The proposed WGM characterization approach in this study paves an efficient way for the development of high-sensitivity WGM sensors to combat the ongoing pandemic and future biohazardous threats.