Scheme 1.

Schematic showing the multiplex detection strategy on SS‐chip. Serum samples from COVID‐19 patients are introduced into SS‐Chip preloading dual‐encoded beads. SS‐Chip immunoassay employs two parallel assays including a bridging assay with color‐encoded‐beads‐conjugated capture antigens (cAgs) and RCA‐product‐tagged detection antigens (dAgs) to detect anti‐N/S1/RBD antibodies (N‐Ab, S1‐Ab, RBD‐Ab) and a sandwich assay with size‐encoded‐beads‐conjugated capture antibodies (cAbs) and RCA‐product‐tagged detection antibodies (dAbs) to detect IL‐6, IL‐1β, PCT, CRP. Beads with various sizes based on RCA displayed different detection ranges from pg mL⁻¹ to μg mL⁻¹.