Chirality as useful and key aspects in molecular biology can be used for biosensing applications [1], [2], [3]. Due to the importance of high resolution as much as low-price biosensors, there were a lot of reports onto the ways to enhance chirality by the aid of new materials and new chiral and achiral nanostructures [4], [5], [6], [7], [8]. Wide range of these nanostructures consist of symmetry breaking ones like as chiral oligomers [9], chiral nanoparticles [10], [11], nanohelix arrays [12], twisted nanorods [13], [14], three dimensional helices [15], [16]; or symmetric ones like as square array of nanoparticle platform [17] are used to enhance circular dichroism signal. It is well known that lacking mirror symmetry or quasi two- or three-dimensional thin films lacking in plane mirror symmetry are main key factors to reach above mentioned chirality. But now there are experimentally and theoretically evidence that surface plasmon polariton waves in achiral structures can show chirality due to asymmetry in field distribution [18], [19], [20]. This chirality can use to enhance signal to noise ratio in sensors based on the changes in metal refractive index as well as dielectric adjacent environment and also to detect the amount of glucose in the human body.

Circular dichroism (CD) in chirality, as the difference between right and left circular polarizations’ transmission, is widely used for biophotonic applications [21] such as the investigation of CD-active interactions between Fipronil and Neuronal cells in a study by Xiuxiu Wang et al. [22]. However, the problem of low SNR still remains a major obstacle to CD sensing. Up to now, various methods have been proposed for SNR amplification, including the use of near field of chiral and achiral nanostructures. Mohammadi et al. in their study theoretically investigated the amplification of the CD signal by both chiral plasmonic and dielectric nanostructures [17]. By the use of helical plasmonic nanostructures as prototypical chiral near-field sources, Martin Schäferling et al. created electromagnetic fields with intrinsic chirality, which then enhanced their interaction with chiral molecules [23]. As well, Maria C. di Gregorio et al. studied the interaction between silver and glutathione nanocubes, to investigate the amplification of chiroptical effects on plasmon-molecule interactions [24]. In another study, using LSPR from gold chiral nanohooks, Gunnar Klös et al. designed a CD sensor with the enhanced refractive index sensitivity due to the reduction of substrate noise [25].

Despite of the high SNR in plasmonic structures, in recent years, dielectric metasurfaces in thin films, perforated ones [26] or Fabry–Pérot interferometer (FPI) or etalon introduce as good candidate instead of metallic plasmonic structures [27], [28]. In all-dielectric metsurfaces, the diffractive scattering of the incident light by nanoparticles causes the lattice surface modes (LSMs) to propagate inside the structure, which these LSMs (such as LSPRs in plasmonic nanostructures) can interfere with the localized excitations of each nanoparticle [29]. Consequently, a coupled scattering resonance occurs, and the width of the reflection or transmission spectra of the all-dielectric structure becomes narrower, which makes this structure a good candidate for biosensing applications. All-dielectric high-index metasurfaces can also supports Mie scattering resonances and thus electric dipole (ED) and magnetic dipole (MD) resonant modes can be occurred. In addition, all-dielectric metasurfaces can also enhance the optical field intensity when the incident wavelength is adjusted to the resonance wavelength.

In this work, a biosensing chip based on all-dielectric metasurface incorporated into the etalon nanostructure was proposed and fabricated using the nanoimprint lithography technique and also a flow cell channel was designed and fabricated for glucose sensing using the proposed all-dielectric nanostructure. Finally, glucose sensing based on circular dichroism (CD) spectroscopy experimentally investigated using the proposed sensing chip. In parallel, the proposed nanostructure was simulated using the finite-difference time-domain (FDTD) method and a good agreement between the experimental and simulation results was achieved.

The designed structure consists of poly-dimethyl-siloxane (PDMS) flexible membrane and TiO2 2D grating structure on both sides of the structure. PDMS is a biocompatible, flexible, and transparent material which can be a good candidate for biosensing applications. This nontoxic and biocompatible material has attracted many applications in various fields such as biology [32], [33], [34], [35], medicine [36], [37], and chemistry [38]. In addition, titanium dioxide (TiO2) was selected as a biosensing material which is a biocompatible material [39], [40], [41] and offers excellent properties for the design and fabrication of all-dielectric metasurfaces [42], [43], [44], [45].

However, there were a lot of report on dielectric matasurface as sensor by phase difference [26] or other optical parameters [46], but usage of CD in miniaturize, low cost and label free all dielectric metasurface and specially etalon structure as glucose sensor proposed for the first time in this report.