Dual-Mode Colorimetric Sensor Based on Ultrathin Resonating Facilitator Capable of Nanometer-Thick Virus Detection for Environment Monitoring

Endowed structural colors in some living organisms provide inspiration for alterable colors depending on the surrounding environment. Although many structural designs for surrounding sensitive colors for various analytes have been introduced, practical applications in a variety of environments require a unified design that can cover the key optical influences of external environmental changes. A bimodal approach to colorimetric sensor design for optimization on different environmental stimuli is presented, based on a single platform composed of a highly lossy medium and a metal. A dual-mode colorimetric facilitator (DMCF) is optimally designed on the basis of the spectral response for each mode depending on the refractive index and thickness, which are optical key elements of changes in the surrounding environment. DMCFs with aqueous solutions and oxide layers are experimentally verified for different refractive indices and thicknesses in nanometer scale. As a biomaterial application, minute in nanometer-thick changes of the virus coated on DMCF are distinguished by color differences. For intuitive recognition of environmental change, the colorimetric indicator is designed as a separate insensitive/sensitive area to reveal hidden patterns beyond a certain thickness of the coated virus in nanometer thick. For scalability/flexibility, a large-area flexible sample is also fabricated on a wafer scale.