Holographic sensors are a class of colorimetric optical probes that allow quantitative, real-time measurements of biomarkers. The sensing devices consist of metal or dielectric nanostructures periodically organised in a functionalised hydrogel film. Such hydrogels may be selected from poly(2-hydroxyethyl methacrylate), polyacrylamide or gelatin, and they can be functionalised to be sensitive to a wide range of analytes including pH, glucose, metal ions and antibodies. When the holographic sensor is illuminated with a broadband white-light source, the grating produces visible-light diffraction and displays a monochromatic colour. The sensor reports on the concentration of analytes by Bragg diffraction peak changes.
Jiang, N., Davis, S., Jiao, Y., Blyth, J., Butt, H., Montelongo, Y., Yetisen, A.K. Doubly Photopolymerized Holographic Sensors, ACS Sensors, 6(3), 915-924 (2021) pdf