Spain: New sensors to detect foreign bodies in food

http://www.freshplaza.com/article/172831/Spain-New-sensors-to-detect-foreign-bodies-in-food

Researchers from the Public University of Navarre (UPNA) and the Navarre-based company Anteral SL, have designed a new system of sensors intended to improve quality controls in the agro-food sector.

These devices make it possible to detect foreign bodies, such as metal, paper, insects, plastic or glass, in a food production chain and identify pathogenic microorganisms in real time. This development, based on terahertz technology, has been possible thanks to a project funded with almost 300,000 Euro by the Spanish Ministry of Economy, Industry and Competitiveness in the framework of the 2013-2016 State Plan for Scientific and Technical Research and Innovation.

The project, called TeraFOOD, was developed by the UPNA's Research Group, formed by Íñigo Ederra Urzainqui, Cebrián García González, Ramón Gonzalo García, Juan Carlos Iriarte Galarregui (head researcher), Carlos Quemada Mayoral and Jorge Teniente Vallinas, working in partnership with the firm Anteral SL, which is specialised in the design of antennas and terahertz technology and has acted as coordinator of the initiative.

These devices are based on terahertz technology, a band of the electromagnetic spectrum located between the microwaves (those needed by mobile phones or TVs) and the infrared waves. The terahertz band is the last unexplored region of the electromagnetic spectrum, due to the difficulty of generating and detecting this type of wave; however, one of the fields where terahertz offers enormous technological potential is in the sensing of substances and materials. This is because almost all molecules have a characteristic trace in this band, which makes it possible to distinguish and identify them.

"The system is a great step forward in this field, since there are no similar devices intended for the carrying out of inspections in the agro-food sector, neither nationally nor internationally," concludes Juan Carlos Iriarte.

This terahertz-based technology is already being used in the area of security to obtain non-intrusive images of hidden weapons. In fact, the UPNA Antenna Group actively participates in the application of this technological development in this sector.

Innovative components for an imaging system in the terahertz range

This image shows an object detection sample. Credit UPNA-NUP

http://www.ecnmag.com/news/2015/08/innovative-components-imaging-system-terahertz-range

Terahertz frequencies offer the unique feature of displaying things that in other frequency ranges, such as the visible, microwave or X-ray ones, would be impossible. So they are able to display a ceramic weapon or a parcel bomb hidden under clothing, or skin cancer in its early stages, and even the properties of certain foods. In her PhD thesis, read at the NUP/UPNA-Public University of Navarre, Itziar Maestrojuán-Biurrun has developed specific technology for imaging applications in this frequency range.

"This thesis has opened up the possibility for the first time of using substrates of this type to implement components of the system, which leads to reduced losses and, therefore, an improvement in the functioning of the mixer," pointed out Itziar Maestrojuan. Specifically, her research has incorporated various innovations: firstly, a terahertz imaging system has been developed using COC (cyclic olefin copolymer) substrates in the implementation of its components; and secondly, it is also the first time that a fourth harmonic mixer in the WR2.2 band, specifically at a frequency of 440 GHz, has been designed, manufactured, measured and published.

Her thesis, "Development of Terahertz Systems for Imaging Applications", was supervised by the professor of Signal and Communications Theory Ramón Gonzalo-García. The work, produced and defended totally in English before a tribunal at the highest level comprising professionals from the United States (Virginia Diodes), Germany (ACST) and the Netherlands (European Space Agency), received a cum laude distinction with an International Doctor mention.

As the researcher explained, any object for the mere fact that it has a temperature above zero degrees Kelvin emits radiation that can be captured by receivers and with which an image can be obtained, thanks to the contrast between what is emitted by various bodies. A camera that works within the terahertz range "could enhance airport security as it can pick out objects hidden in clothing or the skin; it could be used to assist in the take-off of helicopters in the middle of a sandstorm, or could play an important role in medicine (skin cancer detection, caries, passive tomography, etc.).

Good image resolution

Once the viability of using the new substrates in the mixer design had been confirmed, an array (a set of receptors) of 1X8 elements was developed. The operational array comprising eight Schottky diode mixers for imaging application purposes was shown in Spain for the first time.

The thesis concludes with the images taken (for which a quasi-optical system lent by the company Alfa Imaging was also used). "The possibility of taking images with the components designed was also confirmed," said Itziar Maestrojuán. "The results showed good resolution of the objects and variation in the power level depending on their nature."

The user was able to distinguish between elements such as the human body, a metal plate or ceramic material, detect them and identify them by means of their shape. "The images taken in the open air at a distance of 4 metres from the system made it possible to fully distinguish a person and detect a metal plate placed on his/her chest, which offers an alternative for the current airport scanners."

Source: http://www.eurekalert.org/pub_releases/2015-08/ef-icf080615.php

New devices based on metamaterials

http://www.sciencedaily.com/releases/2014/10/141022103352.htm

Victor Torres Landivar, Telecommunications engineer, has designed and manufactured new devices based on metamaterials (artificial materials with properties not found in nature). On drawing up his PhD, defended at the Public University of Navarre (UPNA), he achieved the first experimental demonstration ever with epsilon-near-zero (ENZ) metamaterials. "These materials have surprising characteristics, such as the fact that a wave travelling within them can do so at almost infinite speed and, thus, can be transmitted from one place to another without hardly any loss of energy, no matter how unusual or complicated the shape of the material. The potential applications of these media are numerous; for example, in nanocircuits, electrical levitation or invisibility."

The research focused mostly on the design of new metamaterials in the Terahertz (THz) frequencies, a waveband located between microwave and infrared. "It is a waveband with enormous potential for applications in biomedicine, radio-astronomy and security -- for the detection of explosives and weapons," pointed out Mr Torres. "Being a waveband of relatively recent use, there is a great lack of efficient devices and this is why the results of our research are contributing to filling this gap." The PhD thesis is entitled "Plasmonics and Metamaterials at Terahertz Frequencies."

The properties of the metamaterials do not arise from their composition but from the shape in which their structure is designed. "In this way, materials can be achieved, for example, with negative refraction index and which bend light in the opposite direction to what occurs in natural materials."

The results of the research can be summed up in three large groups: extraordinary transmission metamaterials, ENZ metamaterials, and optical nano-antennae.

According to the author of the research, the extraordinary transmission metamaterials are very thin metallic structures, made up of very small holes. An optimum layout of these holes enables the light to pass through them, but in a very different way than larger holes do. "We have found a special way of interconnecting these holes through meandering-shaped lines that give these metamaterials additional characteristics." Once the behaviour of the new structure is known, a polariser is designed and manufactured, enabling controlling and changing the direction of the light through the structure. "This polariser is capable of working at two different waveband frequencies, with very good waveband characteristics and a really thin thickness, making it a device that keenly competes with and, in most cases, surpasses commercial devices in performance."

As regards the ENZ metamaterials, their properties have been exploited to design and manufacture metallic lenses with high performances. With these lenses the electromagnetic wave passes through very narrow channels which are very close to each other. "The correct engineering of these channels and of the shape of the lens itself confers on it radiation and energy-focusing properties that are greater than those of classical lenses manufactured with other materials." Mr. Torres has designed and manufactured these lenses with a plane concave profile for working at 0.15 Thz. "It was the first experimental demonstration ever with this type of ENZ metamaterials and, moreover, we have proposed theoretically a more advanced design where the reduction of the volume of the lens has been achieved while maintaining similar performance."

Finally, he has worked on the design of nano-antennas. "This involves devices made up of groupings of metallic nanoparticles (normally gold or silver) that behave in a similar manner to the classic radiofrequency antennas, but at optical frequencies." For his PhD thesis he has designed and manufactured a nano-antenna the uniqueness of which is to provide a waveband greater than the rest of the nano-antennae but with a similar concentration of energy. "In this way, it can be used in multiple-frequency spectroscopy experiments. The same nano-antenna simultaneously gives relevant gain in three different spectroscopy experiments (fluorescence, Raman absorption and infra-red); i.e. instead of using three different nano-antennae for each of the experiments, with this kind design just one nano-antenna is sufficient."

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Story Source:

The above story is based on materials provided by Basque Research. Note: Materials may be edited for content and length.

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Journal Reference:

1. Pacheco-Peña V., Torres V., Beruete M., Navarro-Cía M., Engheta N. ε-near-zero (ENZ) graded index quasi-optical devices: steering and splitting millimeter waves. Journal of Optics, 2014, No. 9: 094009