Fabrication and characterization of flexible spray-coated antennas

This paper investigates the potential of using spray coating as a methodology for flexible antenna fabrication. The methodology has advantages compared with other antenna-printing techniques, such as screen-printing and gravure printing (more flexibility in design), or inkjet printing (faster production). The methodology is demonstrated using two different types of folded dipole antennas that are designed to operate in the ultra-high frequency radio-frequency identification (UHF RFID) band. Both antennas show good agreement between simulation and measurement of the spray-coated samples in terms of power reflection coefficient and gain. The two folded dipoles, with and without ground plane, show comparable performance in terms of gain, as similar antennas found in literature. The folded dipole on a ground plane is more stable near conductive surfaces and on the human body. Given these results, we conclude that spray coating is a good technique for printing small to medium sized batches of antennas

Technological Integration in Printed Electronics

Conventional electronics requires the use of numerous deposition techniques (e.g. chemical vapor deposition, physical vapor deposition, and photolithography) with demanding conditions like ultra-high vacuum, elevated temperature and clean room facilities. In the last decades, printed electronics (PE) has proved the use of standard printing techniques to develop electronic devices with new features such as, large area fabrication, mechanical flexibility, environmental friendliness and—potentially—cost effectiveness. This kind of devices is especially interesting for the popular concept of the Internet of Things (IoT), in which the number of employed electronic devices increases massively. Because of this trend, the cost and environmental impact are gradually becoming a substantial issue. One of the main technological barriers to overcome for PE to be a real competitor in this context, however, is the integration of these non-conventional techniques between each other and the embedding of these devices in standard electronics. This chapter summarizes the advances made in this direction, focusing on the use of different techniques in one process flow and the integration of printed electronics with conventional systems

Improving the Manufacture by Flexographic Printing of RFID Aerials for Intelligent Packaging

Flexography is a well-established high-volume roll-to-roll industrial printing process that has shown promise for the manufacture of printed electronics for smart and intelligent packaging, particularly on to flexible substrates. Understanding is required of the relationship between print process parameters, including ink rheology, and performance of printed electronic circuits, sensors and in particular RFID antenna. The complexity of this printing process with its shear and extensional flows of complex inks and flexible substrates can lead to undesirable surface morphology to the detriment of electronic performance of the print. This thesis reports work that progresses the understanding of the complex relationships amongst relevant factors, particularly focusing on the printability of features that have an impact on printed RFID antenna where increases in resistance increase the antennas resonant frequency. Flexography was successfully used to print RFID antenna. However, the large variation in print outcomes when using commercial inks and the limits on resistivity reduction even at the optimal print parameters necessitated the systematic development of an alternative silver flake ink. Increases in silver loading and TPU polymer viscosity grade (molecular weight) increased the viscosity. The ink maintained its geometry from the anilox cell between rollers, on to the substrate and print surface roughness increased. This, however, did not increase resistance of the track due to the high silver loading. Better understanding of the relationship between print parameters, print outcomes, ink rheology and performance of an RFID antenna has been achieved. Increases in silver loading up to 60wt.% improved conductivity. However, further increasing the silver loading produced negligible additional benefit. An adaption of Krieger-Dougherty suspension model equation has been proposed for silver at concentrations over 60wt.% after assessing existing suspension models. Such a model has proven to better predict relative viscosities of inks than Einstein-Batchelor, Krieger-Dougherty and Maron-Pierce equations. Increasing TPU viscosity grade was found to be a promising ink adjustment in the absence of changing print parameters, to produce a more consistent print. Better prediction of ink behaviour will allow for improved control of ink deposition, which for RFID applications can improve ink conductivity, essential for good response to signal. Further developments such as addition of non-flake particles and formulation refinement are required to enable the model ink to match the resistivity of the commercial ink

Fabrication of electronic devices using high volume printing techniques

This thesis studies the possibility of using high volume offset lithographic and flexographic printing to fabricate single and multiple layer electronic devices, and discusses the performance and applications of the printed devices

Nanoparticle sintering methods and applications for printed electronics

Printed electronics refers to the technologies of fabricating electronic and optoelectronic devices by traditional printing methods. Especially roll-to-roll mass-printing is foreseen to enable low-cost devices on flexible substrates. Direct-write patterning methods, such as inkjet printing, inspire potential for cost-savings in R&D prototyping and customization. Various organic and inorganic materials can be printed in liquid form and subsequently cured to obtain desired electric functionalities. For example, metals can be printed as nanoparticle dispersions and sintered to obtain high conductivity. In this Thesis, the applicability of silver nanoparticle inks for printed wiring, interconnections, memories, antennas, and wireless resonant tags, is investigated. The Thesis work involves modeling, simulating, fabricating, measuring and analyzing the prototype structures. Novel methods for sintering nanoparticles are developed. The rapid electrical sintering method, performed by applying voltage over the printed structure, is shown to provide a conductivity increase of more than four orders of magnitude in just milliseconds with the resulting conductivity reaching above 50 % that of bulk silver. The method is further developed to allow for a more practical adaption via contactless coupling at microwave frequencies. A room-temperature sintering method based on the chemical removal of the nanoparticle stabilizing ligand through interaction between the ink and the coating layer of the printing substrate is also presented. The substrate-facilitated sintering method is shown to enable in situ component attachment to printed structures. Inkjet printed RFID antennas and a wireless RF resonant tag fabricated by a combination of roll-to-roll gravure and inkjet printing are shown to provide reading distances sufficient for many practical applications. A novel approach for contactless read-out of printed memory is introduced and demonstrated for a memory structure inkjet printed using silver nanoparticle ink. The information content of the memory is stored in memory bits selectively programmed using the rapid electrical sintering method

Recent advances of wearable antennas in materials, fabrication methods, designs, and their applications: state-of-the-art

The demand for wearable technologies has grown tremendously in recent years. Wearable antennas are used for various applications, in many cases within the context of wireless body area networks (WBAN). In WBAN, the presence of the human body poses a significant challenge to the wearable antennas. Specifically, such requirements are required to be considered on a priority basis in the wearable antennas, such as structural deformation, precision, and accuracy in fabrication methods and their size. Various researchers are active in this field and, accordingly, some significant progress has been achieved recently. This article attempts to critically review the wearable antennas especially in light of new materials and fabrication methods, and novel designs, such as miniaturized button antennas and miniaturized single and multi-band antennas, and their unique smart applications in WBAN. Finally, the conclusion has been drawn with respect to some future directions

Technologies for printing sensors and electronics over large flexible substrates: a review

Printing sensors and electronics over flexible substrates is an area of significant interest due to low-cost fabrication and possibility of obtaining multifunctional electronics over large areas. Over the years, a number of printing technologies have been developed to pattern a wide range of electronic materials on diverse substrates. As further expansion of printed technologies is expected in future for sensors and electronics, it is opportune to review the common features, complementarities and the challenges associated with various printing technologies. This paper presents a comprehensive review of various printing technologies, commonly used substrates and electronic materials. Various solution/dry printing and contact/non-contact printing technologies have been assessed on the basis of technological, materials and process related developments in the field. Critical challenges in various printing techniques and potential research directions have been highlighted. Possibilities of merging various printing methodologies have been explored to extend the lab developed standalone systems to high-speed roll-to-roll (R2R) production lines for system level integration

Review on Carbon-Graphene Nanocomposite based conductive-ink in printed electronics

Energy is the divesting need of human being to make the life easy going and comfortable. But according to the recent scenario, there will be insufficient source of generating energy. Printed electronics is a new concept of printing technology. PE is safest printing ink technology for securing documentation, for making circuits on different subtracts, less time consuming for making and easily detect if counterfeit. Nanoprint technology with semiconductor materials is in improvising and it has been future trend in energy sector with enhancing various properties of nanomaterials. It has been developed in the area of the digital printing technology by using and combining different nanomaterials. With ever-increasing demand for light-weight, small, and transportable devices, the speed of production of electronic and optoelectronic devices is consistently increasing, and alternatives to the current vital, voluminous, fragile, semi semiconducting and clear materials will inevitably be needed at intervals the long run. This review article explains about the carbon-Graphene nanocomposite based conductive ink, which can be a source in digital printing technology to draw various types of circuits and to make different surface to conductive surfaces. It also describes brief information about carbon and Graphene material individually. It also concludes carbon-graphene nanocomposite based conductive ink in printed electronics technology with several literature surveys. &nbsp