Terahertz Asymmetric S-Shaped Complementary Metasurface Biosensor for Glucose Concentration

Abstract

In this article, we present a free-standing terahertz metasurface based on asymmetric S-shaped complementary resonators under normal incidence in transmission mode configuration. Each unit cell of the metasurface consists of two arms of mirrored S-shaped slots. We investigate the frequency response at different geometrical asymmetry via modifying the dimensions of one arm of the resonator. This configuration enables the excitation of asymmetric quasi-bound states in the continuum resonance and, hence, features very good field confinement that is very important for biosensing applications. Moreover, the performance of this configuration as a biosensor was examined for glucose concentration levels from 54 mg/dL to 342 mg/dL. This range covers hypoglycemia, normal, and hyperglycemia diabetes mellitus conditions. Two sample coating scenarios were considered, namely the top layer when the sample covers the metasurface and the top and bottom layers when the metasurface is sandwiched between the two layers. This strategy enabled very large resonance frequency redshifts of 236.1 and 286.6 GHz that were observed for the two scenarios for a 342 mg/dL concentration level and a layer thickness of 20 μm. Furthermore, for the second scenario and the same thickness, a wavelength sensitivity of 322,749 nm/RIU was found, which represents a factor of 2.3 enhancement compared to previous studies. The suggested terahertz metasurface biosensor in this paper could be used in the future for identifying hypoglycaemia and hyperglycemia conditions.

Non-Invasive Glucose Sensing Technologies and Products: A Comprehensive Review for Researchers and Clinicians

“…However, there is a significant obstacle in developing Terahertz (THz) sensors that can detect analytes with high sensitivity due to the substantial difference between the THz wavelength and analyte thickness or quantity within the tissue [58]. Al-Naib [58] addressed this obstacle by developing a Terahertz meta-surface based on s-shaped complementary resonators to investigate glucose concentration levels associated with different diabetes conditions. The research showed significant resonance frequency redshifts of 110.6 GHz and improved wavelength sensitivity compared with previous studies, making it a potential tool for detecting hypoglycemia and hyperglycemia.…”

“…TES relies on the principle that glucose levels affect the body's heat distribution, which in turn affects the emitted thermal radiation (Figure 11). However, there is a significant obstacle in developing Terahertz (THz) sensors that can detect analytes with high sensitivity due to the substantial difference between the THz wavelength and analyte thickness or quantity within the tissue [58]. Al-Naib [58] addressed this obstacle by developing a Terahertz meta-surface based on s-shaped complementary resonators to investigate glucose concentration levels associated with different diabetes conditions.…”

Multiple Fano Resonances in a Metal–Insulator–Metal Waveguide for Nano-Sensing of Multiple Biological Parameters and Tunable Slow Light

“…For practical applications, it is difficult to change the structural parameters of waveguides, but the waveguide's refractive index may be changed much more easily than its structural properties, which makes it possible to accomplish independent tuning of the Fano resonances that are more suited for sensing [47]. The following is the definition of the sensitivity of refractive index sensing [41,48]:…”

Performance analysis and prediction of tunable metasurface filter based on electrochemical metallization

“…Metasurfaces have excellent electromagnetic properties beyond the limitation of natural materials [2], which showing a variety of flexible control of parameters such as amplitude [3], phase [4,5], polarization [6], etc. Therefore, due to the application in the spectrum range from terahertz to visible light [7], such as filters [8,9], biosensors [10][11][12][13], perfect absorbing materials [14,15] * Author to whom any correspondence should be addressed. and optical switches [16,17], metasurfaces have aroused great research interest.…”