Fig. 2.

Chip-based biosensors for potential antigen and antibody detection for COVID-19. a Miniaturized and high-throughput ELISA on a chip-based biosensor. The fingerstick blood is directly applied to an assay chamber. The slide is prepared by printing “stable” spots of capture antibodies (cAb) and “soluble” spots of the fluorescently tagged detection antibodies (dAb) on the polymer brush (1). dAb dissolves and binds to the analyte (2), the complexes diffuse and bind to the respective cAb spots (3), and subsequently (4) generates fluorescent signals. A mobile phone-based reader is coupled with the biosensor to provide quantitative readout. Adapted with permission from [90]. b Multiplexed detection of IgG, IgM, and the viral antigen for SARS-CoV-2 based on fluorescence immunoassay using a centrifugal chip-based biosensor (FMS: fluorescent microsphere). Adapted with permission from [91]. c A low-consumption electrochemical biosensor for antigen detection, which is powered directly by a mobile phone. Adapted with permission from [92]