Approach for quality detection of food byRFID-based wireless sensor tag

Son Dat Nguyen, Thong Tien Pham, Eric Fribourg Blanc,Ngan Nguyen Le, Chien Mau Dang and Smail Tedjini

ELECT

A novel wireless sensor for the detection of food quality is presented.The main idea is to transform radio frequency identification (RFID)tags into RFID sensors, owing to a specific design of the tagantenna. From knowledge of the variation of the permittivity of foodover time through experimental characterisation, it is possible todetect the time from which the food becomes improper for consump-tion based on the read-range measurement of the designed sensingtags. This low-cost ultra-high frequency (UHF) RFID passive sensorwas designed and experimentally tested on plastic-film-wrapped beefmeat. The overall agreement between the experimental and simulationresults shows the potential of this technique for real-world applicationsin food traceability.

Introduction: During the past decade, radio frequency identification(RFID) technology was steadily grown as potential applicationsunfolded. In this context, current RFID ultra-high frequency (UHF)passive tags can store enough amounts of data and present a potentiallylong lifespan [1]. Presented is an approach to evolve the RFID passivetags, ultimately transforming them into sensors, with the aim to applysuch a technique for food quality detection. It is worth noting thatsome electromagnetic techniques in monitoring the freshness of foodproducts have already been introduced [2]. In this Letter, we exploitthe sensitivity of the tag antenna to measure variations in the immediateenvironment of the tag. Then, we present both the theoretical back-ground and the method of design to explain the operational mode ofdetection by using passive UHF RFID tags. Experimental results andimprovement routes are also presented.

Theoretical background: The geometry of a typical UHF tag which isdesigned to be sensitive to its environment, i.e. through the proximitywith the food to be monitored through its packaging, is shown inFig. 1. Based on the data from [3], the permittivity of a certain foodproduct will change as a function of time due to the degradation by bac-teria. As a result, it leads to the change of the antenna’s impedancewhich modifies the matching between the antenna and the RFID chipand, therefore, the power activation of the tag [1]. Essentially, thedesign of the sensor tag is based on the variation of the read-range dis-tance. For this purpose, two tags are designed for different values of thepermittivity of the food sample (beef). Over time, it loses its freshness toreach the state of contamination beyond which it is unfit for consump-tion. The sensor tag has been designed to meet the minimum read-rangeat the state of food contamination with only one tag. However, it is poss-ible to increase the system reliability by adding another tag at distance dfrom the first one. The second tag is also designed to have the minimumread-range at the contamination time, but its radiation pattern is noworthogonal to the maximum direction of gain of the first tag. All ofthe simulations are related to the ETSI regulation of UHF RFIDsystems (resonant frequency at 868 MHz).

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a Different layers of tag antennab Fabricated prototype

Characterisation of meat permittivity: This step is very important forthe design and performance evaluation of the fabricated RFID sensortag. The permittivity of beef (from METRO®, France), under thesame storage conditions (temperature 5 ± 1°C and humidity 50 ± 5%),

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is measured using a HP85070B coaxial probe from Agilent® [4]. pHand permittivity were measured every 12 h from the fresh state, untilcontamination and beyond (10 consecutive days in total). The dielectricpermittivity was measured at four different points and the pH at fourothers. Each measured point was measured three times for both permit-tivity and pH to obtain the median value every 12 h. From the results inFigs. 2a–c, it can be seen that there is a transition in the curve of pHaround 120 h, while the permittivity approaches its maximum valuesin both real and imaginary parts (dielectric constant and loss factor ofpermittivity as in Figs. 2b and c). After the first 120 h, the pH increasessteadily and the permittivity greatly decreases, a accompanied with thebeef developing a bad smell and stickiness. Another notable fact is thatthe pH will exceed the threshold of 6.2 around 120 h. From the externalappearance and the pH standard [5], we can conclude that the contami-nation of beef occurs around 120 h and the permittivity at this momentcan be considered as the physical factor to detect it.

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a pH of beef as function of timeb Dielectric permittivity (permittivity’s real part) against time at 868 MHzc Loss factor (permittivity’s imaginary part) against time at 868 MHz

Simulation design of the RFID sensor tag: First, we develop a simu-lation model with all the parameters for the design of the RFID sensortag imported in CST Microwave Studio®. In this model [6], weplaced the RFID sensor (i.e. two AK3 Tagsys loops on top of twomeander antennas) on the meat with the set values of permittivityfrom the experimental results in Fig. 2. The dielectric permittivity ofthe fresh beef is 56.8 + j22.6 (at start) and the one at contamination is61.8 + j24.0 (at 120 h). Then, we adjusted both the internal dimensionsof each RFID tag and distance d between them from 1 to 8 cm to obtainthe final design of the RFID sensor tag.

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Experimental results and discussion: The optimisation shows that theoptimum distance d between the two tags is roughly 3 cm to maintainthe desired radiation patterns. From Fig. 3, we can see that the read-range of each tag reaches the minimum value at 120 h. Besides, wecan see that the radiation patterns of both tags are almost unchangedwhich keeps the directions of maximum radiation constant and almostperpendicular to each other as a function of time (Fig. 4a). The fabri-cated sensor tag is measured using the setup as follows: the sensor tagis mounted on the beef sample in order to define the 3D read-rangefrom the fresh state to the contamination state (every 12 h in seven con-secutive days) at a distance from an RFID reader Speedway RevolutionR420 of Impinj®. From the measured results in Fig. 3, the contaminationtime of the sensor tag is around 120 h as given by the simulation. Themismatch between simulation and measurement results in Fig. 3 canbe explained by the fact that the permittivity at contamination time isaffected by only a little change in the environmental conditions, suchas temperature and moisture content [3]. Moreover, the directions ofthe maximum read-range are quasi-perpendicular to each other(Fig. 4) which validates the feasibility of this design in real-worldapplications.

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a Simulation of 3D radiation pattern with optimised distance d = 3 cmb Measurement 3D read-range of fabricated prototype

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Conclusion: In this Letter, we proposed an approach for using passiveUHF RFID tags to detect meat contamination through a dual tag sensor.The experimental and simulation results show the potential of this tech-nique for real-world applications in food traceability. On the other hand,sensing strategies can be developed thanks to the use of more tags in thesame sensor. Moreover, the results of this work allow us to consider theuse of this approach for medical applications.

Acknowledgments: This work was supported in part by the VietnamMinistry of Science and Technology (MOST) of Vietnam. AK3Tagsys loops were kindly provided by S. Tedjini and C. Loussert inthe frame of our collaboration.

© The Institution of Engineering and Technology 201328 October 2013doi: 10.1049/el.2013.3328One or more of the Figures in this Letter are available in colour online.

Son Dat Nguyen, Thong Tien Pham, Ngan Nguyen Le and Chien MauDang (Laboratory for Nanotechnology, Vietnam National University –Ho Chi Minh City, Community 6, Linh Trung Ward, Thu DucDistrict, Ho Chi Minh City, Vietnam)

E-mail: ndson@vnuhcm.edu.vn

Eric Fribourg Blanc (MINATEC Campus, CEA-LETI, 17 rue desMartyrs, 38054 Grenoble Cedex 9, France)

Smail Tedjini (Université Grenoble Alpes, LCIS, 50 rue Barthélémy deLaffemas, BP 54, 26902 Valence Cedex 9, France)

References

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2 Ong, K.G., Bitler, J.S., and Grimes, C.A., et al.: ‘Remote query resonant-circuit sensors for monitoring of bacteria growth: application to foodquality control’, Sens. MDPI, 2002, 2002, (2), pp. 219–232

3 Ryynänen, S.: ‘The electromagnetic properties of food materials: areview of the basic principles’, J. Food Eng., 1995, 26, pp. 409–429

4 Hewlett Packard: ‘HP 85070M dielectric probe measurement system’,http://www.cp.literature.agilent.com/litweb/pdf/5091-6247EUS.pdf,accessed December 2012

5 Food and Agriculture Organization of the United Nations: ‘Meat proces-sing hygiene’, http://www.fao.org/docrep/010/ai407e/ai407e25.htm,accessed December 2012

6 Nguyen, D.S., Phan, G.-T., and Pham, T.-T., et al.: ‘A battery free RFIDsensor for quality detection of food product’. Proc. PIERS 2013,Stockholm, Sweden, August 2013, pp. 583–587

ecember 2013 Vol. 49 No. 25 pp. 1588–1589