The COVID-19 pandemic has brought to light a critical need of point-of-care testing. Here, we demonstrate two metasurface-based multi-signal biosensing platforms. The first is based on the extraordinary optical transmission phenomenon of plasmonic nanohole arrays, which provides both optical and electrochemical signals. The second is based on all-dielectric TiO2 metasurfaces, which enables simultaneous triple optical signals: spectral, spatial (geometric parameter of gradient metasurfaces), and colorimetric readouts. The multi-signal readouts are cross-validated and experimentally demonstrated by refractive index sensing and biomolecular detection. Working in the visible spectrum, metasurface-based biosensors point towards ultra-compact and cost-effective solutions suitable for point-of-care testing.
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