Flipped Quick-Response Code Enables Reliable Blood Grouping.

Accurate and rapid blood typing plays a vital role in a variety of biomedical and forensic scenarios, but recognizing weak agglutination remains challenging. Herein, we demonstrated a flipping identification with a prompt error-discrimination (FLIPPED) platform for automatic blood group readouts. Bromocresol green dye was exploited as a characteristic chromatography indicator for the differentiation of plasma from whole blood by presenting a teal color against a brown color. After integrating these color changes into a quick-response (QR) code, prompt typing of ABO and Rhesus groups was automatically achieved and data could be uploaded wirelessly within 30 s using a commercially available smartphone to facilitate blood cross-matching. We further designed a color correction model and algorithm to remove potential errors from scanning angles and ambient light intensities, by which weak agglutination could be accurately recognized. With comparable accuracy and repeatability to classical column assay in grouping 450 blood samples, the proposed approach further demonstrates to be a versatile sample-to-result platform for clinical diagnostics, food safety, and environmental monitoring.