Fig. 2: End-to-end implementation of Meta-Sticker.
From: Sub-terahertz metamaterial stickers for non-invasive fruit ripeness sensing
a, A block diagram of our end-to-end system: a sub-THz scanner measures the reflected signal from the Meta-Sticker. We extract the localized plasmon (dipole) and the propagating plasmon resonances in the reflection spectra. The two-resonance phenomenon occurs due to the inhomogeneous and dissipative dielectric properties of the fruit as the substrate for Meta-Stickers. We translate the measured resonances to the refractive index of the exocarp and mesocarp layers, providing an in-depth and non-invasive insight into the physiological stage of the fruit’s multilayers. Finally, the refractive indices of the mesocarp are mapped to well-known fruit quality metrics (Bx and DM) to estimate the ripeness of the fruit. b, Our experimental set-up for collecting reflection signals from fruits over 20 days from 30 different persimmons, pears and mangoes.
