Chipless Radio Frequency Identification Sensor Research Articles

From Chip-Based to Chipless RFID Sensors: A Review

Radio Frequency Identification (RFID) sensors have received increasing attention in recent years due their wireless battery-free operation, low-profile, simplicity, low-cost, and multimodality sensitivity. They have found their way to everyday applications including smart packaging for food quality assurance, early noxious gas detection, smart bandages for chronic wound assessment, and structural health monitoring. This work aims to provide a review of chip-based and chipless RFID sensor technology and to depict a transition from the former to the later one. This is conducted by highlighting existing challenges for implementation of chipless RFIDs, possible solutions to overcome these problems, and recent development introduced in the literature. Then, it has been demonstrated how RFID sensors in conjunction with artificial intelligence and machine learning can be applied for enhancing RFID tag sensitivity and selectivity to a high degree of accuracy. The focus of this paper is on chipless RFID sensors, and at the end the authors present a direction for future research work.

Chipless RFID Sensors for IoT Sensing and Potential Applications in Underground Mining—A Review

Chipless radio frequency identification (RFID) sensors have enormous potential for underground mining applications since this technology has the potential to meet all the requirements, such as wireless communication, maintenance-free, long lifespan, and battery-free, required to deploy in harsh underground environments. This paper has analysed existing frequency domain chipless RFID sensor technologies to understand suitability for potential applications, such as environmental condition monitoring, support system stability detection, and health monitoring of mining structures in underground mining sites. In light of the analysis, the paper has presented a new classification based on sensing materials and intrinsic sensing parameters such as effective length, coupling, conductivity and permittivity. Furthermore, the analysis has considered accuracy, performance and readability using 3D Electromagnetic (EM) analysis software, CST Studio Suite. Finally, based on our critical analysis and experimental simulations, the paper has identified challenges that need to be addressed by future research for chipless RFID sensors in the underground mining application domain.

Design of a metamaterial chipless RFID sensor tag for high temperature

A high temperature sensor based on a metamaterial is proposed as a chipless radio frequency identification sensor tag that can measure temperature wirelessly. The metamaterial, based on a double circular split ring resonator (SRR), is highly frequency selective and has negative permittivity. The double circular SRR is fabricated on the alumina ceramic substrate, which acted as the temperature sensing material. The permittivity of the material varies with the temperature parameter, resulting in a shift of backscattered resonant frequency of the sensor tag. Simulations verify the feasibility of this sensor tag in the microwave band under electromagnetic stimuli. When the temperature increases from 200 to 1000 °C, the resonant frequency monotone decreases from 6.64 to 6.26 GHz with an average sensitivity of 0.475 MHz/°C. The sensor tag has features such as high temperature, being wireless, passive, of comparatively low-cost, and miniature, with diversified application potential, allowing it to compete with other sophisticated temperature devices in terms of performance.

A Novel Multiresonant Chipless RFID Tag for Directional Strain Measurement on Metal Surface

In this article, a radio frequency identification (RFID) sensor tag for real-time health monitoring of the magnitude and direction of metal surface strain is presented. The chipless RFID sensor tag is composed of metal foil and F4B substrate, which is low-cost and works stably in harsh environments for a long time. Through highly sensitive strain monitoring, the risk can be predicted in the early stage of defect generation. The proposed tag includes a C-type resonator array, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> -type transmission line, and tag antennas. The C-type resonator has different sensitivities in the electrical length direction and width direction. Then, based on this characteristic, the resonator array creates a plurality of characteristic signatures containing strain information by optimizing the geometric parameters of the resonators. The strain information is transmitted to the tag antenna through the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> -type transmission line to complete the wireless communication between the tag and the reader. Finally, the performance of the strain monitoring system is verified by an experimental study. The experiment shows that the average sensitivity of the resonators is −4.94 and 1.14 kHz/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \varepsilon $ </tex-math></inline-formula> in the electric length and width directions, respectively. When the strain is more than 150 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \varepsilon $ </tex-math></inline-formula> , the relative error of magnitude is less than 12.7% and the absolute error of direction is less than 13.3°. Therefore, the proposed chipless RFID tag can monitor the amplitude and direction of strain with higher sensitivity and a simpler structure, for the key structures, such as the high-speed running gear.

Tailoring the Performance of a Nafion 117 Humidity Chipless RFID Sensor: The Choice of the Substrate.

Chipless radio-frequency identification (RFID) sensors are not yet widespread in practical applications because of their limited sensitivity and selectivity when compared to more mature sensing technologies. The search for a suitable material to perform the sensing function has often been focused on the most common materials used in electrochemical sensing approaches, but little work has been done to directly relate the performances of chipless or microwave sensors to the characteristics of the materials used to fabricate them. In this work we are simulating the impact of the substrate material on the performances of a chipless RFID sensor for humidity detection. The dielectric parameters of the substrate material turn out to be very important to maximize the sensor performances, in relation to the operative range of the sensor (based on the desired application) and to the effective dielectric properties of the sensitive material used, we verify the simulated results with measurements of real chipless humidity cells with Nafion 117 sensitive material. We show which types of substrate are preferable for low-humidity detection and which substrates' features are instead fundamental to operate in a wider humidity range.

Radio Frequency Identification Temperature/CO2 Sensor Using Carbon Nanotubes

In the world of digitization, different objects cooperate with the Internet of Things (IoT); these objects also amplify using sensing and data processing structures. Radio frequency identification (RFID) has been identified as a key enabler technology for IoT. RFID technology has been used in different conventional applications for security, goods storage, transportation and asset management. In this paper, a fully inkjet-printed chipless radio frequency identification (RFID) sensor tag is presented for the wireless identification of tagged objects. The dual polarized tag consists of two resonating structures functioning wirelessly. One resonator works for encoding purpose and other resonator is used as a CO2/temperature sensor. The sensing behavior of the tag relies on the integration of a meandered structure comprising of multi-wall carbon nanotubes (MWCNT). The MWCNT is highly sensitive to CO2 gas. The backscattered response of the square-shaped cascaded split ring resonators (SRR) is analyzed through a radar cross-section (RCS) curve. The overall tag dimension is 42.1 mm × 19.5 mm. The sensing performance of the tag is examined and optimized for two different flexible substrates, i.e., PET and Kapton®HN. The flexible tag structure has the capability to transmit 5-bit data in the frequency bands of 2.36-3.9 GHz and 2.37-3.89 GHz, for PET and Kapton®HN, respectively. The proposed chipless RFID sensor tag does not require any microchip or a power source, so it has a great potential for low-cost and automated temperature/CO2 sensing applications.

Tunable Chipless RFID Pressure Sensor Utilizing Additive Manufacturing—Model, Simulation, and Measurement

Each sensing application has its own set of unique requirements and constraints that must be satisfied by its sensor. These requirements can include being wireless, passive, noncontact, customizable, multifunctional, and/or minimally invasive, depending on the application. Chipless radio frequency identification (RFID) tags are a type of microwave sensor that has the potential to meet many of these requirements, especially when additive manufacturing (AM) is employed to create customizable substrates that are sensitive to different ranges of environmental measurands. This work examines the potential efficacy of a proposed chipless RFID pressure sensor design approach that utilizes polymer AM substrates. Complex permittivity and stress–strain measurements were conducted to develop a model that relates the resonant frequency of the chipless RFID sensor to pressure, which in turn allows for the design of sensors with customized sensing ranges and sensitivities. This model is based around a standard rectilinear 3-D polymer-printed infill pattern. Custom-infill patterns can be developed to further tune the sensor performance based on a desired application. Electromagnetic (EM) simulations and measurements of fabricated tags, including one design based on the model with a rectilinear infill pattern and two designs that utilize custom-infill patterns, were conducted to illustrate the efficacy of the developed model and sensor design approach. Several possible sources of inconsistency between measurement and simulation are also investigated.

Characteristic Analysis of a Chipless RFID Sensor Based on Multi-Parameter Sensing and an Intelligent Detection Method.

Chipless radio frequency identification (RFID) technology has been widely used in the field of structural health monitoring (SHM), but most of the current research mainly focuses on the detection of mechanical properties and there are few studies on the multi-physical parameters (for example, temperature and humidity) in the climatic environment around the structure. Thus, it is necessary to design a small and compact sensor for multi-parameter detection. This paper proposes a multi-parameter chipless RFID sensor based on microstrip coupling, which supports 4-bit ID code and integrates two detection functions of temperature and humidity. Through linear normalization fitting, the sensitivity of the sensor is about 2.18 MHz/RH in the ambient relative humidity test and the sensitivity of the sensor is about 898.63 KHz/°C in the experimental test of water bath heating from 24.6 °C to 75 °C. In addition, this paper proposes an engineering application detection method, designs a lightweight dynamic spectrum detection and wireless transmission platform based on a lightweight vector network analyzer (VNA) and realizes the real-time extraction and transmission of RFID spectrum sensing data. The means are more flexible and economical than traditional experimental scenarios.

Chipless RFID Sensors for Wearable Applications: A Review

Radio frequency identification (RFID) is a quickly growing innovative wireless data capturing technology for automatic identification, product tracing, security investigation, automatic toll fee, vehicle tracking, and e-Health. Wearable sensing technology and on-body structures have achieved pervasive responses due to their fabulous potential in the Internet of Things (IoT), healthcare, and smart homes. Inexpensive chipless RFID tags for on-body sensing are the upcoming research for such wearable devices. Its sensing skill offers the unified real-time monitoring of vital signs. This paper reviews various chipless passive RFID tag sensors for wearable applications. The main goal of this research work is to study the basics of chipless RFID sensors and their working principles. Further, chipped RFID sensors are very costly for mass implementation. Hence, chipless tag sensors have grown into a cost-effective and maintenance-free substitute, fulfilling the requirements of the society for the emergent technologies, where lots of these sensors can be used. Understanding the importance in emerging applications, essential materials needed for different sensors, basic circuit models for chipped and chipless sensors, and challenges with limitation of recent chipless RFID sensors are also discussed in this article.

Chipless RFID Sensors for IoT-Based Healthcare Applications: A Review of State of the Art

Currently, there is a great demand for low-cost solutions in connected healthcare and real-time wireless patient monitoring remotely. Radio Frequency Identification (RFID) is a rapidly emerging wireless technique for remote data capturing utilized in multifarious applications such as healthcare, automated identification, object tracking, security and authentication, food packaging, and automobile tracking. The projected cost of conventional RFID technology hampers it from being used widely. Chipless RFID sensors with the Internet of Things (IoT) technology have the full potential to meet the requirements of the growing demand. With the development of present technologies, the IoT-based solutions are no longer a challenging vision that offers various potential benefits to today&#x2019;s world, especially healthcare which is an encouraging field of IoT. The design and development of chipless sensors for health monitoring have gathered the attention of the researchers in last few years. This article provides a comprehensive review of chipless RFID sensors that play a vital role in cost-effective healthcare applications. The working principle of a chipless sensing system, fabrication techniques, and classifications of different chipless RFID sensors along with the smart sensing materials are highlighted. This paper throws light on numerous chipless RFID sensors for IoT-based healthcare applications including their challenges and future directions. In addition to that, a comparison table of recent developments in the area of IoT-based healthcare is prepared.

Potential Chipless RFID Sensors for Food Packaging Applications: A Review

Recently, there is an increasing demand for food safety and quality monitoring in the agrifood sector, needing active and smart packaging. Radio Frequency Identification (RFID) has the potential to become one of the most promising technology for the food industry since it can satisfy all the requirements of a sensor and identification in food safety monitoring, packages tracking, inventory control, early warning, and easy check-out. The purpose of this paper is to introduce the recent advancement of the chipless RFID humidity, temperature, gas, pH, and bio-sensors, as these types of sensors are required for evaluating the quality of the food in the food industry. Additionally, the paper explains the requirements of the food industry for quality monitoring of the food products, covers the existing challenges of chipless RFID sensor technology, and highlights the future direction of the research.

Microwave Characterization of Chitosan Hydrogel and Its Use as a Wireless pH Sensor in Smart Packaging Applications

pH is an important parameter in cold chain applications, identified as a key food freshness indicator, especially in perishables. In view of this, in recent years the traction of low-cost RFID tags has increased, especially in the domain of physical parameter sensing. In this paper, we present the electromagnetic characterization of the chitosan-based hydrogel in ultra-wideband (UWB) frequencies, and its use as a pH sensor with chipless radio frequency identification (RFID) resonators. This paper also shows the complete preparation process of hydrogel, and how chitosan hydrogel changes its physical responses to different pH levels. Moreover, we show the changing hydrogel’s physical properties and its correlation with changes in frequency response, enabling low-cost pH sensing in UWB. Chipless RFID sensors are relatively low-cost, but they offer enormous design flexibility in diversified applications such as cold chain, smart packaging, and digital agriculture.

Wireless Passive Sensors for Food Quality Monitoring: Improving the Safety of Food Products

Food waste amounts to roughly one-third of its total production every year. There is an unprecedented demand to improve long-term storage of food products while preserving quality and safety in every stage of its processing, from postharvesting to preconsumption. Different technologies, such as total viable count (TVC), metal-oxide-semiconductor sensors, fluorescence spectroscopy, dye and polymer-based colorimetric sensors as well as radio-frequency identification (RFID), are currently applied for monitoring food products. This article provides an overview of current developments in near-field and ultrahigh frequency (UHF) wireless passive sensors for monitoring of food quality indices and food spoilage indicators. Solutions based on coupled-coil resonator and UHF chipless RFID sensors with application to bacterial-count detection, volatile gas concentration, humidity, and pH monitoring are highlighted.

Chipless RFID Sensors Based on Multistate Coupled Line Resonators

A chipless radio frequency identification (RFID) sensor commonly consists of a tag ID and smart sensing materials. The electrical properties of these materials vary with the sensing physical parameters, such as temperature, humidity, and pressure. Novel and compact temperature sensor integrated with a chipless RFID tag without either increasing the tag size or decreasing the tag capacity is presented. For sensing purposes, a new microstrip coupled line resonator is suggested to support four state ID data and extra sensing information simultaneously. The resonator consists of a coupled line section and three lines with different-length elements (arms). The longest arm, connected at all times, is particularly designed for temperature sensing, and has resonance frequency f1′. The other two arms are used for encoding four different codes. The resonator can be structured for any of the following possible states — 100, 101, 110, and 111 — demonstrating resonance at f1′, resonance at f1′ and f2, resonance at f1′ and f1, and resonance at f1′, f1, and f2, respectively. The change in f1′ can be directly converted object temperature. A multi-resonator structure with six resonators was designed and implemented for RFID sensor applications. Two of these resonators were designed based on the suggested structure, to include temperature sensing and reference frequency. Experimental tests were performed within the temperature range 22 °C to 60 °C. The sensor exhibits a sensitivity of 742 KHz/°C. Experimental and simulation results confirmed the proposed sensing RFID integration concept.

Chipless RFID Sensors for the Internet of Things: Challenges and Opportunities.

Radio-frequency identification (RFID) sensors are one of the fundamental components of the internet of things that aims at connecting every physical object to the cloud for the exchange of information. In this framework, chipless RFIDs are a breakthrough technology because they remove the cost associated with the chip, being at the same time printable, passive, low-power and suitable for harsh environments. After the important results achieved with multibit chipless tags, there is a clear motivation and interest to extend the chipless sensing functionality to physical, chemical, structural and environmental parameters. These potentialities triggered a strong interest in the scientific and industrial community towards this type of application. Temperature and humidity sensors, as well as localization, proximity, and structural health prototypes, have already been demonstrated, and many other sensing applications are foreseen soon. In this review, both the different architectural approaches available for this technology and the requirements related to the materials employed for sensing are summarized. Then, the state-of-the-art of categories of sensors and their applications are reported and discussed. Finally, an analysis of the current limitations and possible solution strategies for this technology are given, together with an overview of expected future developments.

A synthesis of AgNP-rGO-PANI nanocomposite and its use in fabrication of chipless RFID sensor: current research progress

Chipless RFID (Radio Frequency Identification) tag has attracted significant attention due to the low manufacturing cost. By eliminating the use of integrated circuit (IC), chipless RFID tag can offer competitive price in order to completely replace barcode systems. Besides, integration of physical parameter sensors with chipless RFID will open up a new domain for controlling and monitoring perishable items. It can also be fully printable by using inkjet-printed technology. The inkjet-printed technique is one of the most promising technological solutions for the realization of chipless RFID with low-cost advantage. Various types of conductive inks with different fillers such as metal nanoparticles, carbon nanotubes (CNT), and polymer have been developed for printed electronics. It needs deep investigation and study in designing low-cost but robust by using conductive ink on a low-cost substrate. The aim of this review is to claim research gap related to how AgNP-rGO-PANI (Silver Nanoparticle - Reduced Graphene Oxide - Polyaniline) nanocomposite has both scientific and economic advantages. The inkjet-printed method using conductive inks with nanocomposite fillers synthesized from semiconductor materials such as graphene, silver nanoparticles, and polyaniline on a thin sheet of low-cost substrate. This review provides an overview of synthesis methods of AgNP-rGO-PANI nanocomposite, structure and design of chipless RFID sensor, and chipless RFID sensor fabrication methods.

A Review of Chipless Remote Sensing Solutions Based on RFID Technology.

Chipless Radio Frequency Identification (RFID) has been used in a variety of remote sensing applications and is currently a hot research topic. To date, there have been a large number of chipless RFID tags developed in both academia and in industry that boast a large variation in design characteristics. This review paper sets out to discuss the various design aspects needed in a chipless RFID sensor. Such aspects include: (1) Addressing strategies to allow for unique identification of the tag, (2) Sensing mechanisms used to allow for impedance-based response signal modulation and (3) Sensing materials to introduce the desired impedance change when under the influence of the target stimulus. From the tabular comparison of the various sensing and addressing techniques, it is concluded that although many sensors provide adequate performance characteristics, more work is needed to ensure that this technology is capable/robust enough to operate in many of the applications it has been earmarked for.

Multiresonance Chipless RFID Sensor Tag for Metal Defect Characterization Using Principal Component Analysis

One of the challenges in structural health monitoring (SHM) is that defects, such as metal cracks and corrosions, can occur with multiple material properties and multilayer structure, entangled with influences from the reader system and the environment. This paper presents a multiresonance chipless radio frequency identification (RFID) sensor tag and the chipless RFID sensor reader applying principal component analysis (PCA) for multiparameter estimation in metal defect characterization. The proposed sensor tag is composed of the crossed diagonal dipole patches and the L-shaped patches generating six resonance peaks within 2-6-GHz band. The frequency signature of the sensor tag is acquired and processed by a chipless RFID reader implemented using an ultra-wideband impulse radar (UWB-IR) transceiver module. We demonstrate that the multiresonance chipless RFID sensor tag in conjunction with PCA-based feature extraction and selection can be applied for the characterization of metal crack with different widths and orientations. Furthermore, the proposed technique can find a robust feature indicating corrosion stages under a coating layer regardless of the sample orientation. This paper paves the way for multiparameter defect sensing and monitoring using a chipless RFID sensor system.

The Realization of Chipless RFID Resonator for Multiple Physical Parameter Sensing

We present the design of asymmetric circular split ring resonator as a chipless radio frequency identification (RFID) sensor tag design that can be deployed to measure multiple physical parameters wirelessly in ultrawideband frequencies. Secondarily, the proposed tag design can extend to be used as a chipless RFID tag with actual data encoded for product identification purposes. The proposed resonator design consists of four complementary split circular rings. Each gap between the rings acts as a capacitive sensor which is optimized to have a resonance with a high-quality factor. Each resonance can be considered as a sensor to deploy smart materials that are sensitive to different environmental physical parameters, which can be operated in wireless conditions. The fabricated chipless RFID sensor provides a higher ${Q}$ factor, aligned with the optimized simulation model. Chipless RFID sensors are comparatively low-cost, but they provide enormous design flexibility in diversified applications. The proposed design holds a great promise for sensing multiple physical parameters in a remote setting.

Chipless Radio Frequency Identification (RFID) Sensor for Angular Rotation Monitoring

A novel, chipless, Radio Frequency Identification (RFID) sensor is proposed for monitoring angular rotation. The rotation state is recovered by collecting the cross polar response of a tag, based on a periodic surface composed of a set of dipoles. The encoding mechanism allows the sensor to be very robust, even if it is applied on metallic objects, or in an environment with strong multipath. The proposed sensor does not require a large operational bandwidth. Instead, only a small set of reading frequencies are required. The number of reading frequencies required is dependent on the number of the employed dipoles. It is demonstrated that the rotation state of an object can be monitored within a span of 180 degrees, with up to a three-degree resolution, by employing a chipless RFID sensor comprising of four dipoles. The far field reading scheme and the absence of any electronics device allow the sensor to be employed in harsh environments.