Lithographically printed voltaic cells - A feasibility study

It has been shown that circuit interconnects and various passive components can be fabricated on a variety of flexible substrates using the offset lithographic process. This paper reports on a feasibility study investigating the manufacture of voltaic cells deposited via offset lithography

Customizing 3D-Printing for Electromagnetics to Design Enhanced RFID Antennas

none5This document discusses some of the advances in additive manufacturing 3D-printing for electromagnetic applications that have been investigated in the literature in the last few years. Starting from the research activity of the authors on this topic, this work summarizes and showcases the effectiveness of the 3D-printing technology in electromagnetics, with reference to UHF RFID technology. Specifically, the first part of the work deals with Fused Deposition Modeling (FDM) printing technique and faces the problem of the characterization of 3D-printable materials using a made-in-lab instrument based on the T-Resonator theory, which has been purposely designed to be 3D-printed. Once verified the dielectric properties of substrates realized with common 3D-printable materials, two techniques to improve their electrical permittivity are explained. Moreover, the possibility to realize fully 3D-printed RFID devices based on the use of novel 3D-printable materials with noteworthy conductive properties is discussed. Then, two new 3D-printed antennas are presented and discussed highlighting some of the advantages of 3D-printing in electromagnetics. Finally, the application in RFID of another promising 3D-printing technology called Digital Light Processing (DLP) and based on the photopolymerization of liquid resins is discussed as well.openR. Colella ; F. P. Chietera ; F. Montagna ; A. Greco ; L. CatarinucciColella, R.; Chietera, F. P.; Montagna, F.; Greco, A.; Catarinucci, L

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

Printing studies with conductive inks and exploration of new conducting polymer compositions

In addition to low cost and high volume, continuous production of devices such as transistors and RFID tags, printable electronics show promise in the fabrication of a multiplicity of sensors, displays, photovoltaic arrays, smart cards, etc. Due to flexibility and insensitivity to substrates, the use of organics in printed electronics has opened up a number of new opportunities in novel applications. In the present work, the process capability of flexography and offset lithography for patterning conductive materials was determined using small scale equipment (rotary letterpress and duplicator respectively). Process parameters including: type of substrate, line widths, line gaps, print thickness, directional effects, etc. were investigated. It was thus shown that the high volume printing processes of offset lithography and flexography can be used to obtain functional printed conductive patterns. In order to have greater control over ink composition and physical characteristics than was afforded by commercially available silver metal filled conductive inks, polyaniline (PANI) was synthesized by interfacial polymerization. Printable flexographic inks were formulated therefrom and a PANI ink was used in the flexographic printing of a working gas sensor. The conductivity of these inks was lower than that of silver filled metallic inks. This mitigated their utility in their utility in the printing of functional RFID antennae. Poly (thiophene-2, 5-diyl) (PT) and its derivatives are perhaps the most extensively studied class of conducting polymers and find applications in a variety of organic electronic devices. In the present work, an unprecedented approached to the synthesis and formulation of solution processible polythiophene (PT) compositions was explored. Conducting composites of polythiophene were synthesized by oxidative coupling of bithiophene, catalyzed by Fe3+ bound to the amphiphilic segment of functional block copolymers. Thus, amphiphilic block copolymers such as polystyrene-b-polyethylene oxide (PS-PEO) and polystyrene-b-polyacrylic acid (PS-PAA) complexed with Fe3+ were utilized as templates in the formation of soluble/redispersible prototype inks. The distribution of the conductive phase is, in principle, determined by the morphology of the block copolymer. The composites were characterized by DSC, UV-vis and IR spectroscopy. PT formed in the presence of these amphiphilic block copolymers was oxidised using suitable doping agents. The compositions however failed to exhibit significant conductivity. A number of challenges must be overcome in order to realize the potential economic benefits of using organic polymers in large scale electronic printing applications. The conductivity of inks based on organic conducting polymers can be increased by increasing the overall volume fraction of the conductive entity. The adhesion of the PANI compositions on various substrates could be improved by addition of a binding agent at a level that does not adversely affect the conductivity of the inks. Opportunities afforded by a post treatment/curing step may be considered and explored. Lastly, the ink formulation parameters and printing process variables should be optimized

Bioengineered Textiles and Nonwovens – the convergence of bio-miniaturisation and electroactive conductive polymers for assistive healthcare, portable power and design-led wearable technology

Today, there is an opportunity to bring together creative design activities to exploit the responsive and adaptive ‘smart’ materials that are a result of rapid development in electro, photo active polymers or OFEDs (organic thin film electronic devices), bio-responsive hydrogels, integrated into MEMS/NEMS devices and systems respectively. Some of these integrated systems are summarised in this paper, highlighting their use to create enhanced functionality in textiles, fabrics and non-woven large area thin films. By understanding the characteristics and properties of OFEDs and bio polymers and how they can be transformed into implementable physical forms, innovative products and services can be developed, with wide implications. The paper outlines some of these opportunities and applications, in particular, an ambient living platform, dealing with human centred needs, of people at work, people at home and people at play. The innovative design affords the accelerated development of intelligent materials (interactive, responsive and adaptive) for a new product & service design landscape, encompassing assistive healthcare (smart bandages and digital theranostics), ambient living, renewable energy (organic PV and solar textiles), interactive consumer products, interactive personal & beauty care (e-Scent) and a more intelligent built environment

NFC based Polymer Strain Sensor for Smart Packaging

This paper presents a polymer strain sensor integrated with an NFC tag to detect strain semi-quantitatively. The strain sensor is fabricated using flexible and transparent polymer Polydimethylsiloxane (PDMS) microchannel having conductive polymer poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as an active material. The sensor was tested with different bending conditions and it was found that the resistance increases with higher bending. A maximum of 3 order change in resistance was observed for ~100 bending. The sensor was finally tested using a custom-developed passive NFC tag having an LED connected in series with the strain sensor and powered from the reader via the NFC antenna in the tag

Low cost patterning of thin film

A novel route for the low-cost patterning of electrical thin films has been established. The process has been developed principally for the manufacture of thermocouples using high-speed reel-to-reel industrial techniques, but could be applied to the manufacture of a wide range of electronic devices including radio frequency identification (RFID) antennae, electrical interconnect, and passive electronic components. The procedure exploits high-volume processes directly to print self-removing masking layers. The process offers substantial advantages over traditional thin-film patterning methods including faster, cheaper production runs. Raw material use and wastage are greatly reduced, affording environmental benefits

Structural Analysis and Material Characterization of Silver Conductive Ink for Stretchable Electronics

Stretchable electronic systems have become more popular in various applications such as medical, fabric, flexible sensors for personalized health care, etc. There are two major parts of flexible and stretchable circuit boards that are substrate (a plastic material) and conductive ink (formulated polymer with conductive metal). According to electrical measurements, conductive ink plays a very important role in stretchable electronic equipment. The main objective of this paper is to develop a silver (Ag) based conductive ink and characterize its mechanical and electrical properties. Conductive ink is prepared by mixing an epoxy resin, cross – linking agent, additives (adhesion promoter), organic solvent, catalyst and silver flakes all together. ASTM D412 Type C dog bone shaped cutter is used to make three samples of conductive ink. The stress-strain analysis of conductive ink is carried out using universal testing machine (UTM). The conductivity is measured using two-point probe digital multi-meter. Also, the microstructural analysis, morphology and characterization are done by scanning electron microscopy (SEM). The images are taken after curing and tensile testing. The formulated ink possesses high conductivity and stretchability up to 137% strain. The achieved conductivity of the ink is 4.167×104 S/m. The maximum stress before failure, yield stress, Young’s and tangent moduli are calculated as 1.195 MPa, 0.86 MPa, 5.72 MPa and 2.08 MPa, respectively. The SEM analysis indicates that the distribution of silver particles is uniform and in a good density throughout the sample

The Effect of Fabrication Method on Passive UHF RFID Tag Performance

In passive Radio Frequency Identification (RFID), transponders or tags are used to label objects to be identified. In this study passive tag antennas were produced using etching, screen-printing, and gravure printing methods. The threshold and backscattered signal strengths of the tags were measured to determine the effect of different manufacturing methods on the tags' performance. Conductivity, skin depth, thickness, and the quality of the conducting layer have a major effect on tag performance. Each manufacturing method sets its own boundary conditions on the processibility of the high quality conduction layer and such conditions need to be considered in tag design. Tag design also affects the manufacturing parameters used in the different techniques. The results of the study show that each of the studied fabrication methods can be used to manufacture reliable RFID tags