Imaging-based optical barcoding for relative humidity sensing based on meta-tip

Abstract

In a wide range of applications such as healthcare treatment, environmental monitoring, food processing and storage, and semiconductor chip manufacturing, relative humidity (RH) sensing is required. However, traditional fiber-optic humidity sensors face the challenges of miniaturization and indirectly obtaining humidity values. Here, we propose and demonstrate an optical barcode technique by cooperating with RH meta-tip, which can predict the humidity values directly. Such RH meta-tip is composed of fiber-optic sensor based on surface plasmon resonance (SPR) effect and graphene oxide film as humidity sensitizer. While SPR sensor is composed of multimode fiber (MMF) integrated with metallic metasurface. Dynamic time warping (DTW) algorithm is used to obtain the warp path distance (WPD) sequence between the measured reflection spectrum and the spectra of the precalibrated database. The distance sequence is transformed into a pseudo-color barcode, and the humidity value is corresponded to the lowest distance, which can be read by human eyes. The RH measurement depends on the collective changes of the reflection spectrum rather than tracking a single specific resonance peak/dip. This work can open up new doors to the development of a humidity sensor with direct RH recognition by human eyes.

Revisiting the Design Strategies for Metasurfaces: Fundamental Physics, Optimization, and Beyond

“…[ 139 ] In addition, metafibers can be used for biosensors [ 140 ] and relative humidity sensors. [ 141 ] Metafibers with functionalities, such as OAM multiplexing or demultiplexing, may find many interesting applications. Thus far, metafibers have been designed only considering the tangential component of polarization, but the propagating fiber modes have longitudinal polarization, as can be expected from the propagation based on total internal reflection.…”

Recent Advances and Prospects of Optical Metasurfaces

“…As functional platforms, metasurfaces provide more possibilities for lab-on-fiber technology, which may boost their application in medical detection, sensing, nanofabrication, and optical manipulation . Two approaches are mainly adopted to integrate the metasurface on the optical end facet: the transfer − and direct processing methods. ,, The transfer method separately prepares the fiber end facet and metasurface and then transfers the metasurface on the fiber end facet. During the transfer process, high-precision translational and rotational stages and an optical microsystem are required to ensure rigorous alignment. , Optical adhesives represented by photocurable polymers are used to attach metasurfaces with fiber ends. , On this basis, a metalens, prism, and single-mode fiber (SMF) are integrated to construct a side-view nano-optic endoscope .…”

“…As functional platforms, metasurfaces provide more possibilities for lab-on-fiber technology, which may boost their application in medical detection, sensing, nanofabrication, and optical manipulation . Two approaches are mainly adopted to integrate the metasurface on the optical end facet: the transfer − and direct processing methods. ,, The transfer method separately prepares the fiber end facet and metasurface and then transfers the metasurface on the fiber end facet.…”

“…Metasurfaces Integrated with Optical Fibers. As functional platforms, metasurfaces provide more possibilities for lab-onfiber technology, which may boost their application in medical detection, 165 sensing, 166 nanofabrication, 60 and optical manipulation. 61 Two approaches are mainly adopted to integrate the metasurface on the optical end facet: the transfer 165−169 and direct processing methods.…”

“…165 Based on the metasurface, the transverse resolution approaches the diffraction limit. Furthermore, versatile sensors based on metasurface-based fiber tips, such as humidity sensors 166,168 and magnetic field sensors, 169 have been developed. Considering the labor consumption and alignment error in the transfer method, the direct processing method based on TPL, which directly writes the nanostructures on the fiber ends with a specific holder, is increasingly popular.…”