Sensing viruses using terahertz nano-gap metamaterials

Abstract

We demonstrate highly sensitive detection of viruses using terahertz split-ring resonators with various capacitive gap widths. Two types of viruses, with sizes ranging from 60 nm (PRD1) to 30 nm (MS2), were detected at low densities on the metamaterial surface. The dielectric constants of the virus layers in the THz frequency range were first measured using thick films, and the large values found identified them as efficient target substances for dielectric sensing. We observed the resonance-frequency shift of the THz metamaterial following deposition of the viruses on the surface at low-density. The resonance shift was higher for the MS2 virus, which has a relatively large dielectric constant. The frequency shift increases with surface density until saturation and the sensitivity is then obtained from the initial slope. Significantly, the sensitivity increases by about 13 times as the gap width in the metamaterials is decreased from 3 µm to 200 nm. This results from a combination of size-related factors, leading to field enhancement accompanying strong field localization.

Terahertz Sensing Based on Metasurfaces

“…[76], this technique could be extended to the detection of bacteria in aqueous environments through the functionalization of the metasurface with receptors that allow the detection of certain bacteria. [88] with a with a gap small enough to sense viruses (left). Optical Mater.…”

“…[88], THz-TDS measurements to demonstrate the detection of the bacteriophage viruses PRD1 and MS2, which have dimensions of 60 nm (λ THz /5000) and 30 nm (λ THz /10 000) and are double-stranded and single-stranded DNA viruses, respectively. This would imply the creation of new metasurfaces with a metal gap size 10 3 orders of magnitude lower than the designs produced for the detection of bacteria, adding some difficulty to the manufacturing process.…”

“…This would imply the creation of new metasurfaces with a metal gap size 10 3 orders of magnitude lower than the designs produced for the detection of bacteria, adding some difficulty to the manufacturing process. [88], the dielectric constant of the different viruses was obtained by studying the saturation-thickness behavior of the resonant frequency of THz metamaterials. [88], THz-TDS measurements to demonstrate the detection of the bacteriophage viruses PRD1 and MS2, which have dimensions of 60 nm (λ THz /5000) and 30 nm (λ THz /10 000) and are double-stranded and single-stranded DNA viruses, respectively.…”

“…Three years after the work commented above, Park et al carried out, as in ref. [88] using the relationship between the relative permittivity and the frequency normalized shift for metamaterial devices, the dielectric constants of the PRD1 and MS2 virus layers were found to be 3.48 and 3.83 at 0.8 THz, respectively. The metamaterial patterns consisted of an array of SRRs with a gap of 200 nm (see scheme in the left panel of Figure 5b).…”

“…As shown in the second and third panels of Figure 5b, the response saturation depends on the gap size, although in all cases there is a redshift of the dip as the concentration increases. [88], there is still a long way to go and numerical simulations would be necessary to understand the reasons behind the large difference between PRD1 and MS2 sensitivities. As observed, the frequency shift is larger as the gap width decreases due to the higher interaction with the viruses placed in that area.…”