M13 bacteriophage-based high-sensitivity Fabry-Pérot etalon for detecting humidity and volatile organic compounds.

Various sensor applications have been developed for protection against hazardous environments, and research on functional materials to enhance performance has also been pursued. The M13 bacteriophage (M13) has found utility in sensor applications like disease diagnosis and detection of harmful substances due to its potential for controlling interaction with target substances through adjustments in electrochemical and mechanical properties via genetic engineering technology. However, while optimizing reactivity or binding affinity between M13 and target materials is crucial for sensor performance enhancement, precise dynamic measurement methods for this were lacking. This study demonstrates the application of an M13-based dynamic actuator in a Fabry-Pérot etalon (M13-FPE) as a spacer for precise measurement of humidity and reactivity to volatile organic compounds (VOCs). The transmission spectrum is optimized by adjusting the reflectance and cavity gap size (d) of the two mirrors comprising the M13-FPE, and changes are measured in a rainbow-color-dotted (RCD) pattern using a customized spectrometer. Utilizing the peak wavelengths of the RCD pattern, the change in d is dynamically and precisely measured, revealing approximately 3% and 0.3% swelling for ethanol and isopropyl alcohol, respectively. M13 demonstrates binding affinities of 827 ppb and 158 ppb for ethanol and isopropyl alcohol, respectively, with its low reactivity measured precisely, exhibiting an error of 0.03 nm using the peak wavelength change rate.