Embargo
Terahertz sensing based on metasurfaces
(Wiley, 2020) Beruete Díaz, Miguel; Jáuregui López, Irati; Institute of Smart Cities - ISC
The terahertz (THz) band has very attractive characteristics for sensing and biosensing applications, due to some interesting features such as being a non-ionizing radiation, very sensitive to weak interactions, thus, complementing typical spectroscopy systems in the infrared. However, a fundamental drawback is its relatively long wavelength (10–1000 µm) which makes it blind to small features, hindering seriously both thin-film and biological sensing. Recently, new ways to overcome this limitation have become possible thanks to the advent of metasurfaces. These artificial structures are planar screens usually made of periodic metallic resonators and whose electromagnetic response can be controlled at will by design. This design freedom allows metasurfaces to surpass the restrictions of classical THz spectroscopy, by creating fine details comparable to the size of the thin films or microorganisms under test. The strong field concentration near these small metasurface details at resonance makes them highly sensitive to tiny variations in the nearby environment, allowing for an enhanced detection more accurate than classical THz spectroscopy. The main advances in THz metasurface sensors from a historical as well as application-oriented perspective are summarized. The focus is put mainly on thin-film and biological sensors, with an aim to cover the most recent advances in the topic.
Open Access
Tripod-loop metasurfaces for terahertz-sensing applications: a comparison
(MDPI, 2020) Jáuregui López, Irati; Orazbayev, Bakhtiyar; Pacheco-Peña, Víctor; Beruete Díaz, Miguel; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
The high electric field intensity achieved on the surface of sensors based on metasurfaces (metasensors) makes them an excellent alternative for sensing applications where the volume of the sample to be identified is tiny (for instance, thin-film sensing devices). Various shapes and geometries have been proposed recently for the design of these metasensors unit-cells (meta-atoms) such as split ring resonators or hole arrays, among others. In this paper, we propose, design, and evaluate two types of tripod metasurfaces with different complexity in their geometry. An in-depth comparison of their performance is presented when using them as thin-film sensor devices. The meta-atoms of the proposed metasensors consist of a simple tripod and a hollow tripod structure. From numerical calculations, it is shown that the best geometry to perform thin-film sensing is the compact hollow tripod (due to the highest electric field on its surface) with a mean sensitivity of 3.72 × 10−5 nm−1. Different modifications are made to this structure to improve this value, such as introducing arms in the design and rotating the metallic pattern 30 degrees. The best sensitivity achieved for extremely thin film analytes (5–25 nm thick) has an average value of 1.42 × 10−4 nm, which translates into an extremely high improvement of 381% with respect to the initial hollow tripod structure. Finally, a comparison with other designs found in the literature shows that our design is at the top of the ranking, improving the overall performance by more than one order of magnitude. These results highlight the importance of using metastructures with more complex geometries so that a higher electric field intensity distribution and, therefore, designs with better performance can be obtained.
Open Access
Lipid and protein oxidation marker compounds in horse meat determined by MIR spectroscopy
(MDPI, 2020) Jáuregui López, Irati; Zulategui Beñarán, Fernando; Beriain Apesteguía, María José; Sarriés Martínez, María Victoria; Beruete Díaz, Miguel; Insausti Barrenetxea, Kizkitza; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD
This work broadens the study of lipid and protein oxidation marker compounds in foal meat, employing the technology of Attenuated Total Reflectance-Fourier Transform Mid-Infrared Spectroscopy (ATR-FT/MIR, shortened in the following as MIR). As a main objective, marker compounds from 23 foals were extracted and their absorbance spectra were measured to establish prediction models (calibration and validation) between them and classical quantification analysis of the compounds. Another objective was to ascertain whether a previous extraction of the marker compounds before executing their MIR analysis is preferable compared to direct MIR measurements on the raw meat samples. In this context, marker compound results (TBARS between 0.4387 and 2.1040, and carbonyls between 4.07 and 4.68) showed more consistent predictive models than the ones achieved using quantitative analysis of the spectra obtained from the raw meat. Lipid oxidation compounds predictive models obtained in this work offered an R-cv(2) of 63.18% and protein oxidation R-cv(2) obtained in this project showed a value of 54.24%. Thus, MIR technology arises as a promising tool to identify and quantify products derived from lipid and protein oxidation in fresh foal meat.
Open Access
THz tripod metasurfaces for sensing applications: from the basic, to more elaborated designs
(IEEE, 2021) Jáuregui López, Irati; Orazbayev, Bakhtiyar; Pacheco-Peña, Víctor; Beruete Díaz, Miguel; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
In this work, we propose, design, and evaluate three types of : three types of metasurfaces using tripod-shaped unit cells when working as thin-film sensing devices. The three meta-atoms of the proposed metasensors area simple solid tripod, a hollow tripod, and a hollow tripod structure with arms.The best design showed a mean numerical sensitivity of 1.42 × 10−4nm for extremely thin samples, meaning an improvement of 381% with respect to the initial designs. These results highlight the importance of using metastructures with complex geometries that enable high-intensity electric field distributions over the whole metasurface.
Open Access
Metageometries for polycyclic aromatic hydrocarbons detection at THz range in food systems
(IEEE, 2021) Jáuregui López, Irati; Insausti Barrenetxea, Kizkitza; Beriain Apesteguía, María José; Beruete Díaz, Miguel; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD; Ingeniería Eléctrica, Electrónica y de Comunicación
Polycyclic aromatic hydrocarbons, when present in food systems, have been shown to have a detrimental effect on human health, producing carcinogenic elements. So, the implementation of processes for their detection and identification is of vital importance. Nowadays, there are different methodologies for this purpose, but they consist of expensive and time-consuming processes. Due to their enhanced sensitivity and more accurate detection capability, metageometries operating in the terahertz band arise as a new methodology to identify and detect different chemical or biological substances. In this work, we propose a labyrinth metageometry able to detect different polycyclic aromatic hydrocarbons collected in European regulations as the most critical compounds with high experimental sensitivity. Our design is also capable to distinguish between different compounds at the same concentration. This work leads the way to the design of new metastructures able to improve the current detection limits, and thus obtain a new methodology, easier and less time-consuming that the actual methods.
Open Access
Labyrinth absorber based on metageometries metasurface for fungi detection
(IEEE, 2020) Jáuregui López, Irati; Rodríguez Ulibarri, Pablo; Kuznetsov, Sergei A.; Beruete Díaz, Miguel; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
In this paper a labyrinth metasurface based in the new paradigm of metageometries is designed to operate in the Terahertz (THz) band as a biosensor. First, a numerical study is carried out to study the performance of the metasurface as a refractometer when working in two different configurations: transmission and reflection. Then, its performance as a fungi detector is evaluated and a comparison with other devices is performed, showing that the sensitivity and Figure of Merit (FOM) can be enhanced by the use of these kind of devices, in comparison with the classical approach of metaatoms. Particularly, the designed structure is able to detect 5 fungi elements arbitrarily distributed on the unit cell, which is equivalent to a concentration of 0.004/μm 2 , improving the results available in the literature by a factor of more than 4.