What are the advantages of graphene RFID tags

Graphene RFID is emerging as a transformative innovation amid the rapid development of smart cities, Industry 4.0, and the Internet of Things (IoT), which has given rise to a large demand for intelligent RFID identification products. RFID, also known as Radio Frequency Identification technology, is a non-contact automatic data collection method and one of the core technologies of IoT. Its biggest advantage is fast information capture—requiring no mechanical or optical contact, relying entirely on wireless communication to simultaneously collect data from hundreds or even thousands of objects per second with high accuracy. Currently, RFID is widely applied across logistics, transportation, security, mobile payments, and nearly all industries.

Domestic and foreign research status

The United States is an active promoter of RFID tag application, its RFID standard establishment, hardware and software technology development and application areas are at the forefront of the world. The European RFID standard follows the American dominated EPCglobal standard. Europe and the United States for RFID research and development is mainly focused on the development of standards, chip manufacturing, reader manufacturing and system integration. China is the world's largest supplier of RFID tags, RFID tags accounted for about 60% of the world's total production, especially high-frequency RFID tags, our country basically realized from the chip to the antenna of all localization. Popularize the application of RFID system is the main bottleneck of the price of tags, size and environmental adaptability.

At this stage, the domestic common use of copper wire winding method and aluminum foil etching method to manufacture RFID tags, foreign basic use of ceramic sintering method. Common problems are:

(1) pollution of the environment.

(2) Labeling substrate single, limited application areas;.

(3) Low manufacturing efficiency.

(4) Large label size; and

(5) High cost.

(6) low manufacturing precision.

In the past few years, many research institutions at home and abroad that the conductive silver paste screen printing manufacturing RFID tags is to achieve low-cost tags, miniaturization, high precision, adaptability, mass production of the most effective technology. Although the image reproduction in the field of printing technology is fast, efficient, fine lines, overprinting accuracy, however, due to the poor conductivity of conductive silver paste as well as the limitations of the conductive mechanism can only be used with a high silver content of conductive silver paste and a low number of mesh lines of the screen mesh, by the ink viscosity, extensibility, mobility, squeegee pressure, mesh stretching, mesh line interference and other dozens of factors that affect the printed RFID tags conductive line Structural deformation, boundary roughness, short-circuit breaks, the actual radiation efficiency and theoretical radiation efficiency is a big difference.

Overview of domestic and foreign research, almost no scientific and effective control means for the above problems, therefore, at present almost no successful cases of industrialization of RFID tags with this process. In summary, on the one hand, RFID tags market demand is becoming more and more vigorous, on the other hand, RFID tags manufacturing technology still exists in low efficiency, high cost, pollution of the environment, a single substrate and other issues, the market needs a new type of manufacturing technology to break through the contradiction between demand and supply.

1.1 Trend and demand analysis

With the University of Manchester, UK Nobel Prize winner Andre? Sir Andrei Heim and Sir Konstantin Novoselov, Nobel Prize winners from the University of Manchester, UK, have successfully developed a new manufacturing technology. Sir Andrei Heim and Sir Konstantin Novoselov, Nobel Prize winners at the University of Manchester in the United Kingdom, have successfully developed highly conductive graphene materials, the decline in graphene prices and improved product quality greatly stimulate downstream product applications, such as various types of conductive circuits, sensors, medical monitors, and other graphene electronic products are emerging in an endless stream. As graphene material has a microscopic topological structure, so that it has high conductivity, its conductive mechanism is different from the conductive mechanism of metallic silver particles.

1.2 Advantages

Graphene is powdered and processed into a filled composite conductive paste, which has two major advantages:

(1) strong compatibility. Graphene paste can be printed on almost all substrates such as plastic film, paper, ceramics, cotton, wood, etc.;.

(2) Cost-effective. Compared with the existing conductive silver paste, graphene paste has better conductive properties and greater cost advantages.

As graphene production technology continues to mature, the cost continues to decrease, graphene conductive paste will gradually occupy the market share. It is expected that by 2020 the graphene application market size in the field of conductive paste will reach 200 million yuan. At present, some foreign manufacturers of RFID systems have been developed to re-enable graphene paste printed RFID tags of key technologies and industrialization research, such as the British BGTMaterialsLimited (BGTM) company. However, no other domestic company has industrialization research and development of this technology for the time being.

At present, China's graphene production capacity is rapidly expanding, there are a number of large-scale domestic production of graphene manufacturers. For example: Ningbo Mercury Science and Technology Co., Ltd, Chongqing Moshi Technology Co., Ltd, Hongna New Material Technology Co., Ltd, Jinan Moshi New Material Technology Co., Ltd, Suzhou Grifon Nano Technology Co., Ltd, Nanjing Xianfeng Nano Technology Co., Ltd, Changzhou 2D Carbon Science and Technology Co., Ltd, etc., each company's graphene production can reach 100 tons / year. According to the data of “2017-2022 China Internet of Things Industry Market Outlook and Investment Opportunity Research Report” released by China Business Industry Research Institute, China's RFID market scale in 2018 will reach 60 billion yuan.

Based on this, by analyzing the performance parameters of RFID tags, optimizing the printing suitability of graphene conductive paste, and applying gravure printing technology to achieve green, high-volume, high-efficiency, high-quality, low-cost, and suitable for a variety of substrates, the new manufacturing technology of RFID tags has become an inevitable development trend in the industry.

02 Project Research Methods

2.1 Slurry formulation, modulation and dispersion regulation of graphene conductive paste

As graphene characteristics with conductive silver powder has a very different appearance and conductive properties, so that graphene as a substrate for the formulation of conductive pastes, process technology is also very different. The hydrophobicity of graphene will make graphene nanosheets very easy to produce agglomeration through strong van der Waals forces, the use of effective solvents can prevent the agglomeration of graphene, so as to make it a stable graphene dispersion. The ideal solvents are mainly N-methylpyrrolidone (NMP) and dimethylformamide (DMF). This project proposes to disperse graphene by using DMF/NMP as the solvent and adding stabilizers (e.g., ethylcellulose, etc.) to the graphene slurry formulation, with a view to solving the problem that graphene powder is easily agglomerated and not easily dispersed. A laser particle size meter was used to test the granularity of the slurry and its dispersion to ensure the dispersion of graphene slurry particles.

Add UV initiator, photosensitive resin and other components in graphene conductive slurry, optimize its mixing ratio, so that graphene conductive slurry can be cured quickly under UV light, reduce the drying temperature of the printed RFID tags, shorten the drying time, improve the production efficiency, and can be used to print RFID tags on a variety of substrates, such as paper, plastic film, silk fabric, and so on. Change the slurry connecting material and additives, modulation of graphene conductive slurry viscosity, viscosity, fluidity, surface tension, drying, thixotropy, rheology, granularity and other printing suitability, the use of viscosity cups or urethane viscometer, slurry viscosity meter, the surface of the Zhang to meet the requirements of gravure printing.

2.2 RFID tag antenna design based on graphene conductive paste printing

The main parameters affecting the electrical performance of RFID tag antenna are: antenna shape, size and structure, material properties, operating frequency, bandwidth, polarization direction, directionality, gain, wavelength width, impedance, sensitivity, quality factors and the application environment, etc., and the design of RFID tags needs to weigh the above parameters. The design of RFID tags needs to weigh the above parameters. In the simulation software HFSS or ADS, enter the antenna line width, line spacing, bending size, feed gap, feed loop size, electromagnetic signal receiving and feedback material conductivity, dielectric constant and other design parameters, computer simulation simulation, computer simulation simulation to obtain the UHFRFID tags return loss and energy distribution, so as to determine the characterization of the electrical performance of RFID tags parameters and establish data model. Study the influence of graphene conductive paste formulation and printing process parameters on antenna performance. Study the influence of ink film thickness on skin effect and antenna performance. By studying the impedance characteristics of graphene ink layer at different chemical potentials, especially the high reactance characteristics of the UHF band on the RFID tag antenna gain.

2.3 Regulation of Gravure Printing Parameters Based on Graphene Conductive Paste

According to the printing suitability of graphene conductive paste, as well as the structural parameters of the computer simulation design of RFID tags, the number of screen lines, the depth of the screen holes and the shape of the screen cavities of the appropriate gravure printing cylinder are determined, the amount of inking is calculated, and the thickness of the paste film layer is adjusted. For paper, plastic film (such as PET, PI, CPP, etc.), silk fabrics and other different substrates, adjust the intaglio printing when winding and unwinding tension, printing rubber impression roller pressure, paste thixotropic viscosity, doctor blade contact angle, printing speed, positioning overprinting and a series of printing process parameters, to get the most optimal printing process program.

2.4 Optimize the ink film drying temperature and roller pressing pressure

As the printed conductive ink layer is dried and cured to a certain extent, and then calendered by the roller, the surface morphology can be changed to improve the ink layer densification, and substantially improve the electrical conductivity, but the ink film that is being researched and pressed is prone to lead to contour amplification and conductor deformation. Adjust the graphene conductive ink layer in the UV curing channel temperature and time, test the ability to increase the conductivity and the degree of deformation of the ink layer contour, optimize the ink film curing temperature, time and research pressure and other process parameters.

2.5 Analyze and test the performance of RFID tags

Take the printed samples, paste the chip in the Tagformance and other network analyzers to test its operating frequency, bandwidth, polarization direction, directionality, gain, width of the wave petal, impedance, quality factor bandwidth, directionality, gain, return loss, quality factor, sensitivity, and other electrical performance parameters, to test its reading in different application environments. distance for verification and correction.

Summary

After the above research methods and technical routes, with a view to obtaining RFID tags with high conductivity and meeting the demands of the Internet of Things industry, and realizing large-scale industrialized manufacturing of RFID tags, the manufacturing process is completely free of waste and ensures green environmental protection. The technological iteration of graphene RFID tags will surely become the next windfall of the Internet of Things industry.