A colorimetric biosensing system based on a porous silicon (PSi) rugate filter is demonstrated. Using an imaged-based technique that monitors RGB intensity, a spectral shift less than 0.25nm can be reliably detected. The porous silicon rugate filter demonstrates a sensitivity of 310 nm/RIU, which corresponds to a detection limit near 7×10-4 RIU. In this work, an external light source and camera are employed for proof-of-concept demonstration. By utilizing a smartphone camera LED and smartphone camera as the light source and detector, respectively, this system could serve as an effective, low-cost, point-of-care diagnostic tool.
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