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This review encompasses additive manufacturing techniques for crafting 5G electronics, showcasing how these methods innovate device creation with novel examples. A wearable phased array device on commonplace 3D printed material is described, with integrated microfluidic cooling channels used for thermal regulation of integrated circuit bulk components. Mechanical and electrical tunability are exemplified in an origami-inspired phased array structure. A 3D printed IoT cube structure shows the flexibility in the number of geometries additively manufactured 5G devices can adhere to. Finally, integrating 3D optical lenses with 5G electronics is shown. [ABSTRACT FROM AUTHOR]

The rapid development and deployment of 5G/mm-Wave technologies for communication, sensing and energy harvesting applications have been on the rise. Consequently, the need for low-cost, scalable, agile and compact RF modules has become more prominent than ever. This paper presents a review of recent efforts in utilizing additive manufacturing techniques such as inkjet printing to sustainably accelerate the massive deployment of 5G/mm-Wave. First, a novel flexible and massively scalable multiple-input, multiple-output (MIMO) tile-based phased array enabled by additively manufactured microstrip-to-microstrip transitions is presented. Next, a novel Rotman-Based harmonic mmID tag for Ultra-Long-Range localization is presented. Finally, low-power, low-cost mm-Wave backscattering modules for localization and orientation sensing are demonstrated. [ABSTRACT FROM AUTHOR]

The recent developments in mmWave and Internet of Things (IoT) technologies have dramatically increased the interest and demand for radio frequency (RF) devices that can be used for applications such as smart cities, energy harvesting, and ubiquitous wireless sensor networks. Additive manufacturing technologies (AMT) plays an important role to support these applications, as they allows to significantly reduce fabrication costs and times while enabling the achievement of devices with more complex geometries and the possibility of using a wide variety of materials. This publication reviews recent developments of state-of-the-art wireless devices including reconfigurable antennas, frequency-selective surfaces and highly scalable phased arrays enabled by AMT capabilities. It also discusses the benefits of AMT in the fabrication of interconnects that are suitable for packaging of fully-integrated antennas. [ABSTRACT FROM AUTHOR]

Shape-changing mechanical metamaterials have drawn the attention of researchers toward the development of continuous-range tunable frequency selective surfaces (FSSs). In this paper, a novel tunable FSS utilizing an origami-inspired "eggbox" structure is presented featuring four-degrees of freedom that can change the frequency response of two orthogonal linear polarizations. The centrosymmetric "eggbox" structure can be folded or rotated along two axes that lead to unprecedented reconfigurability compared to traditional Miura-Ori-based structures which have fewer degrees of control. The utilized cross-shaped dipole FSS element shows enhanced bandwidth, support for orthogonal linear polarization, and ease of fabrication. The prototype is fabricated using a low-cost fully additive inkjet printing process with silver nanoparticle conductive ink. The outcome of this study shows a 25% frequency tunable range over two polarization directions. The design can be an ideal spatial filtering candidate for advanced ultra-wideband terrestrial and space applications. [ABSTRACT FROM AUTHOR]

This article presents the first time that an millimeter-wave (mm-wave) multichip module (MCM) with on-demand “smart” encapsulation has been fabricated utilizing additive manufacturing technologies. RF and dc interconnects were fabricated using inkjet printing, while the encapsulation was realized using 3-D printing. Inkjet-printed interconnects feature superior RF performance, better mechanical reliability, and on-demand, low-cost fabrication process. Numerous test vehicles were initially produced to evaluate these additive manufacturing technologies and compare them with traditional ribbon bonding, exhibiting a superior $|\text{S}21|$ performance throughout the whole operation range up to 40 GHz with a peak of 3.3 dB better gain for a Ka-band low noise amplifier (LNA). A fully functioning front-end MCM was fabricated using the same inkjet-printed interconnect technology, which features smart encapsulation technology fabricated using the 3-D printing and integrated on-demand “smart” encapsulation for electromagnetic interference (EMI) mitigation. The proof-of-concept MCM demonstrates exceptional performance taking advantage of a low-cost, on-demand additive manufacturing method that requires minimal tooling and process steps, which can drastically accelerate the time to market for future 5G and Internet-of-Things applications. The methodologies presented in this article could potentially enable rapid production of high-performance, high-frequency customizable circuit packaging structures with on-demand “smart” features, such as self-diagnostics, EMI/EMC filtering, and integrated sensors. [ABSTRACT FROM AUTHOR]

With the development of inkjet-/3D-/4D-printing additive manufacturing technologies, flexible 3D substrate with complex structures can be patterned with dielectric, conductive and semi-conductive materials to realize novel RF designs. This paper provides a review of state-of-the-art additively manufactured passive RF devices including antennas and frequency selective surfaces (FSS), couplers, where origami-inspired structure enables unprecedented capabilities of on-demand continuous frequency tunability and deployability. This paper also discusses additively manufactured active RF modules and systems such as inkjet printed RF energy harvester system with high sensitivity and efficiency for Internet of Things (IoT), smart cities and wireless sensor networks (WSN) applications, inkjet-printed RF front ends, and inkjet-printed mm-wave backscatter modules. [ABSTRACT FROM AUTHOR]

This publication provides an overview of additive manufacturing techniques including Inkjet, 3D and 4D printing methods. The strengths, opportunities and advantages of this array of manufacturing techniques are evaluated at different scales. We discuss first the applicability of additive manufacturing techniques at the device scale including the development of origami inspired tunable RF structures as well as the development of skin-like conformal, flexible systems for wireless/IoT, Smartag and smart city applications. We then discuss application at the package scale with on package printed antennas and functional packaging applications. Following this, there is a discussion of additive manufacturing techniques in applications at the die scale such as 3D printed interconnects. The paper is concluded with an outlook on future advancements at the component scale with the potential for fully printed passive components. [ABSTRACT FROM AUTHOR]

This article outlines the design, processing, and implementation of inkjet and 3D printing technologies for the development of fully printed, highly integrated millimeter-wave (mm-wave) wireless packages. The materials, tools, and processes of each technology are outlined and justified for their respective purposes. Inkjet-printed 3D interconnects directly interfacing a packaging substrate with an integrated circuit (IC) die are presented using printed dielectric ramps and coplanar waveguide transmission lines exhibiting low loss (.6-.8 dB/mm at 40 GHz). Stereolithography 3D printing is presented for the encapsulation of IC dice, enabling the application-specific integration of on-package structures, including dielectric lenses and frequency selective surface-based wireless filters. Finally, inkjet and 3D printing technology are combined to present sloped mm-wave interconnects through an encapsulant, or through mold vias, achieving a slope of up to 65° and low loss (.5-.6 dB/mm at 60 GHz). The combination of these additive techniques is highlighted for the development of scalable, application-specific wireless packages. [ABSTRACT FROM AUTHOR]

Nowadays, the explosive growth of Internet-of-Things-related applications has required the design of low-cost and low-power wireless sensors. Although backscatter radio communication is a mature technology used in radio frequency (RF) identification applications, ambient backscattering is a novel approach taking advantage of ambient signals to simplify wireless system topologies to just a sensor node and a receiver (RX) circuit eliminating the need for a dedicated carrier source. This paper introduces a novel wireless tag and RX system that utilizes broadcast frequency modulated (FM) signals for backscatter communication. The proposed proof-of-concept tag comprises of an ultralow-power microcontroller (MCU) and a RF front-end for wireless communication. The MCU can accumulate data from multiple sensors through an analog-to-digital converter, while it transmits the information back to the RX through the front-end by means of backscattering. The front-end uses ON–OFF keying modulation and FM0 encoding on ambient FM station signals. The RX consists of a commercial low-cost software-defined radio which downconverts the received signal to baseband and decodes it using a suitable signal processing algorithm. A theoretical analysis of the error rate performance of the system is provided and compared to bit-error-rate measurements on a fixed transmitter-tag-RX laboratory setup with good agreement. The prototype tag was also tested in a real-time indoor laboratory deployment. Operation over a 5-m tag-reader distance was demonstrated by backscattering information at 2.5 kb/s featuring an energy per packet of 36.9~\mu \textJ . [ABSTRACT FROM PUBLISHER]

A novel wearable and flexible energy autonomous on-body sensing network is proposed featuring full operability through energy harvesting from a hand-held 464.5-MHz UHF two-way talk radio. Three different functions are provided utilizing the hand-held two-way talk radio as the only energy source for our proposed system. There are two types of energy harvesters (EHs) proposed for the presented system. The first EH that is mounted on the sensing capable backscattering RFID tags harvests the 464.5-MHz signal energy to drive the tags; the second EH that can be worn on hands harvests the same 464.5-MHz signal to produce both the dc power and the carrier signal. The second EH is more efficient than conventional ambient RF energy harvesting architectures because for the first time, both the dc and the second harmonics generated by the rectifier are utilized to enable two additional functions. The generated second harmonic is used to interrogate backscattering RFID tags for on-body sensing, while the dc power is used to power an RF amplifier in order to enhance the second harmonic to effectively extend the sensing and communication range. For the proof-of-concept demonstration, the measured dc and the second harmonic, 929 MHz, output power from the proposed EH are 17.5 and 1.43 dBm, respectively, while a two-way talk radio is 9 cm away. The measured second harmonic output power is increased to 13 dBm utilizing the harvester-powered RF amplifier, and the reading range of the custom backscattering sensor tag is extended to more than 70 m. Also, the interrogation of multiple sensor tags and the wireless detection of ammonia gas utilizing an inkjet printed flexible ammonia sensor are demonstrated showing the wide range of applications of the proposed approach. [ABSTRACT FROM PUBLISHER]

Ambient RF energy harvesting is a potential energy source for low-power and battery-less wireless sensors, enabling a range of applications from monitoring to security as part of the Internet-of-Things (IoT) scenario. One of the main challenges of ambient RF energy harvesting is the requirement of operation over a multitude of frequency bands of low ambient power densities resulting in a very wide aggregate operating bandwidth. In this paper, design examples of novel ultra-wideband energy harvesters are demonstrated with octave and decade bandwidths in the UHF and low microwave spectrum. The RF-dc conversion efficiency is maximized by tailoring the dimensions of a nonuniform transmission line used to provide broadband impedance matching. The design challenges in terms of impedance matching based on the Bode-Fano theoretical limit, losses and miniaturization are highlighted. Two prototypes are presented and their performance is evaluated. The octave band rectifier showed a measured RF-dc conversion efficiency of more than 60% over a frequency band of 470 to 860 MHz at 10-dBm input power. The decade band rectifier fabricated on Kapton substrate using inkjet printing featured a higher than 33% efficiency over a frequency band from 250 MHz to 3 GHz at 10-dBm input power. [ABSTRACT FROM PUBLISHER]

By combining radio-frequency identification (RFID) and paper-microfluidics technologies, a low-cost first-of-its-kind platform for comprehensive liquid sensing, i.e., the “smart test strip,” is presented, which enables portable wireless real-time liquid sensing with handhold devices (e.g., cell phones), and integration of various multifunctional electrical and chemical sensors, for numerous Lab-on-Chip applications, including manufacturing control, environmental monitoring, and point-of-care medical diagnostics. The fabrication of RFID tags and two types of microfluidics are accomplished by a single inkjet-printing process in a cost-effective environmental-friendly additive manufacturing approach, which makes possible the production of disposable, lightweight, and flexible sensing platforms. Taking advantage of the proposed smart test strips platforms, we demonstrate two proof-of-concept high-performance electrical sensors based on interdigitated electrode topologies: a resistivity-based sensor with a 1782 $\Omega$/( $\Omega$*m) sensitivity; nevertheless, the proposed permittivity-based sensor with a 15%/$\epsilon _r$ sensitivity, but the proposed integrated wireless platform, can facilitate the integration of even more chemical and electrical sensors. In addition, two on-strip antenna prototypes have been designed, optimized, and tested to work at 2.4 GHz and 13.56 MHz, respectively. Furthermore, the wireless interrogation of a complete proof-of-concept smart test strip is presented, which shows an excellent sensing resolution of 1.33 $\Omega$ over the range of 0–1371 $\Omega$. [ABSTRACT FROM PUBLISHER]

Although wireless sensor networks (WSNs) have been an active field of research for many years, the modules incorporated by WSN nodes have been mainly manufactured utilizing conventional fabrication techniques that are mostly subtractive, requiring significant amounts of materials and increased chemical waste. The new era of the Internet of Things (IoT) will see the fabrication of numerous small form factor devices for wireless sensing for a plurality of applications, including security, health, and environmental monitoring. The large volume of these devices will require new directions in terms of manufacturing cost and energy efficiency, which will be achieved with redesigned, energy-aware modules. This paper presents the state of the art of printed passives, sensors, energy harvesting modules, actives, and communication front ends, and summarizes the challenges of implementing modules that feature low power consumptions without compromising the low fabrication cost. The plethora of the modules presented herein will facilitate the implementation of low cost, additively manufactured, energy-aware IoT nodes that can be fabricated in large volumes with green processes. [ABSTRACT FROM AUTHOR]

In this review, the particular importance and associated opportunities of additively manufactured radiofrequency (RF) components and modules for Internet of Things (IoT) and millimeter-wave ubiquitous sensing applications is thoroughly discussed. First, the current advances and capabilities of additive manufacturing (AM) tools are presented. Then, completely printed chipless radio-frequency identification (RFID) systems, and their current capabilities and limitations are reported. The focus is then shifted toward more complex backscattering energy autonomous RF structures. For each of the essential components of these structures, that encompass energy harvesting and storage, backscattering front ends, passive components, interconnects, packaging, shape-chaging (4-D printed) topologies and sensing elements, current trends are described and representative stateof- the-art examples reported. Finally, the results of this analysis are used to argue for the unique appeal of AM RF components and systems toward empowering a technological revolution of costefficient dense and ubiquitous IoT implementations. [ABSTRACT FROM AUTHOR]

This paper aims to demonstrate that novel additive manufacturing (AM) technologies like metal adhesive laminate and multilayer inkjet printing can be effectively exploited to fabricate high-performing radio-frequency passive components on flexible substrates. Both processes are substrate independent and therefore suitable for manufacturing circuits on several unconventional materials, such as photo-paper. In addition, their complementary features can be combined to develop a novel hybrid process. Proof-of-concept AM prototypes of passive components, such as capacitors and inductors, exhibiting quality factors over 70, never achieved before on paper, and self-resonant frequencies beyond 4 GHz are described. The maximum inductance and capacitance per unit area are 1.4 nH/mm2 and 6.5 pF/mm2, respectively. Moreover, an AM RF mixer with a conversion loss below 10 dB is demonstrated still on paper substrate. The mixer, fabricated with the copper adhesive laminate method, operates at 1 GHz and exploits a lumped balun transformer connected to two packaged diodes in series. [ABSTRACT FROM PUBLISHER]

In this effort, the authors implement the first ultralong-range chipless sensing sticker, by providing more than an order of magnitude increase in reading range, compared with the state of the art. The theoretical advantages of the use of millimeter-wave frequencies for high-performance chipless radio-frequency identification (RFID) sensor implementations are first argued before both a new fully inkjet-printed flexible device, based on the Van-Atta reflectarray structure, as well as a new chipless RFID polarimetric interrogation, and time-frequency data-processing approach is then presented and implemented, for operation in the Ka-band. The array, fully inkjet printed on Kapton HN polyimide, was demonstrated as being robust to variations of interrogation angle (between ±70° from normal), as well as to bending. With its demonstrated range, in excess of 30 m, and its proven adequacy for dense multitag and multisensing implementations in indoor environments, the structure may set the foundation for the emergence of flexible printable low-cost sensing smart skins for the Internet of Things. [ABSTRACT FROM PUBLISHER]

This letter presents two high-gain, multidirector Yagi-Uda antennas for use within the 24.5-GHz ISM band, realized through a multilayer, purely additive inkjet printing fabrication process on a flexible substrate. Multilayer material deposition is used to realize these 3-D antenna structures, including a fully printed 120- μm-thick dielectric substrate for microstrip-to-slotline feeding conversion. The antennas are fabricated, measured, and compared to simulated results showing good agreement and highlighting the reliable predictability of the printing process. An endfire realized gain of 8 dBi is achieved within the 24.5-GHz ISM band, presenting the highest-gain inkjet-printed antenna at this end of the millimeter-wave regime. The results of this work further demonstrate the feasibility of utilizing inkjet printing for low-cost, vertically integrated antenna structures for on-chip and on-package integration throughout the emerging field of high-frequency wireless electronics. [ABSTRACT FROM PUBLISHER]

This paper demonstrates the combination of additive manufacturing techniques for realizing complex 3D origami structures for high frequency applications. A 3D-printed compact package for enclosing radio frequency (RF) electronics is built, that features on-package antennas for RF signal reception (for harvesting or communication) at orthogonal orientations. Conventional 3D printing technologies often require significant amounts of time and supporting material to realize certain structures, such as hollow packages. In this work, instead of fabricating the package in its final 3D form, it is 3D-printed as a planar structure with “smart” shape-memory hinges that allow origami folding to a 3D shape after heating. This significantly reduces fabrication time and effectively eliminates the need for supporting material, thus minimizing the overall manufacturing cost. Metallization on the package is performed by directly inkjet printing conductive inks on top of the 3D-printed surface with a modified inkjet-printed process without the need for surface treatment or processing. Inkjet-printed on-package conductive features are successfully fabricated, that are combined with RF energy harvesting electronics to showcase the proof-of-concept of utilizing origami techniques to build fully 3D RF systems. The methodologies presented in this paper will be enabling the manufacturing of numerous real-time shape-changing 3D complex structures for electromagnetic applications. [ABSTRACT FROM PUBLISHER]

A complete design and additive fabrication process of flexible wearable radio-frequency (RF) energy harvesters for off-the-shelf 2 W two-way talk radios utilizing inkjet printing technology is discussed in this paper. As a result of numerous output dc power measurements of fabricated proof-of-concept prototypes, a maximum output power of 146.9 mW and 43.2 mW was achieved with an H-field and E-field harvester, respectively. Also, the effect of misalignment between receiver and hand-held radio on harvesting performance is discussed in detail. To verify their potential in real-world wearable autonomous RF modules, the operation of E- and H-field energy harvesters was verified by utilizing an LED and a microcontroller communication module under on-body and on-bottle conditions, and the effect of the energy harvesters on the performance of the harvested communication systems was inspected through received power measurements in an anechoic chamber. [ABSTRACT FROM AUTHOR]

This paper presents the design of low-cost, conformal UHF antennas and RFID tags on two types of cork substrates: 1) natural cork and 2) agglomerate cork. Such RFID tags find an application in wine bottle and barrel identification, and in addition, they are suitable for numerous antenna-based sensing applications. This paper includes the high-frequency characterization of the selected cork substrates considering the anisotropic behavior of such materials. In addition, the variation of their permittivity values as a function of the humidity is also verified. As a proof-of-concept demonstration, three conformal RFID tags have been implemented on cork, and their performance has been evaluated using both a commercial Alien ALR8800 reader and an in-house measurement setup. The reading of all tags has been checked, and a satisfactory performance has been verified, with reading ranges spanning from 0.3 to 6 m. In addition, this paper discusses how inkjet printing can be applied to cork surfaces, and an RFID tag printed on cork is used as a humidity sensor. Its performance is tested under different humidity conditions, and a good range in excess of 3 m has been achieved, allied to a good sensitivity obtained with a shift of >5 dB in threshold power of the tag for different humid conditions. [ABSTRACT FROM PUBLISHER]

In this paper, a review of recent improvements on inkjet-printed microfluidic-based tunable/sensing RF systems is reported. The devices, such as Radio Frequency IDentification (RFID) passive wireless tags, coplanar patch antennas, bandstop filters, and loop antennas, are all fabricated by combining the inkjet printing technology on photographic paper for metallization and bonding layers, and laser etching for cavities and channels manufacturing. A novelty is also introduced for the loop antennas where the photographic paper is replaced with a polymer based substrate [i.e., (Poly(methyl-methacrylate))], to reduce the substrate losses for the RF part and solve the issue of paper hydrophylia. Along this paper an evolution toward higher working frequencies and higher detecting performance is shown, demonstrating a sensitivity up to 0.5\%/\varepsilon r with at most 6\,\mu \text L of liquid in the channel. [ABSTRACT FROM PUBLISHER]

Inkjet printing on flexible paper and additive manufacturing technologies (AMT) are introduced for the sustainable ultra-low-cost fabrication of flexible radio frequency (RF)/microwave electronics and sensors. This paper covers examples of state-of-the-art integrated wireless sensor modules on paper or flexible polymers and shows numerous inkjet-printed passives, sensors, origami, and microfluidics topologies. It also demonstrates additively manufactured antennas that could potentially set the foundation for the truly convergent wireless sensor ad-hoc networks of the future with enhanced cognitive intelligence and “zero-power” operability through ambient energy harvesting and wireless power transfer. The paper also discusses the major challenges for the realization of inkjet-printed/3-D printed high-complexity flexible modules as well as future directions in the area of environmentally-friendly “Green”) RF electronics and “Smart-House” conformal sensors. [ABSTRACT FROM PUBLISHER]

In this letter, the inkjet-printing procedure is used to implement microwave circuits on low-cost fibrous substrate, cardboard. As a first step for environmentally friendly electronics applications, the high-frequency properties of the cardboard substrate are extracted using the two-transmission-line method and dielectric probe measurement. To provide an accurate model for the inkjet-printed conductors, the conductivity and thickness of the printed silver traces are analyzed. The surface of the substrate is pretreated using a dielectric ink to reduce the penetration of the conductor ink into the fibrous substrate and to diminish the conductor loss at high frequencies. As a technology demonstrator, a patch antenna is printed on a cardboard substrate, and the simulation and measurement results are compared to study the reliability of the obtained parameters. After initial experimental verification, simulation models were fine-tuned in order to provide a predictive method for design and fabrication of low-cost RF circuits. The achieved model can be used to design and fabricate low-cost RF structures on fibrous environmentally friendly substrates. [ABSTRACT FROM AUTHOR]

This paper introduces the first-of-its-kind wireless passive sensing platform combining radio frequency identification (RFID), microfluidics, and inkjet printing technology that enables remote fluid analysis and requires as little as 3 \muL of fluid. The demonstrated variable microfluidic capacitors, resonators, and RFID tags are fabricated using a novel rapid, low-cost, and low-temperature additive inkjet process, making them disposable. However, even with their disposable nature, the RF microfluidic devices exhibit repeatability and long-term reusability for accurately detecting water, various alcohols, and % content of water/alcohol mixtures down to 1% water in ethanol. While the main discussion is on fluid sensing, the demonstrated components can also be used in fluid-tunable RF applications. [ABSTRACT FROM AUTHOR]

Water-based carbon nanotube (CNT) is highly desirable for inkjet printing devices due to its environmentally benign and low-cost features. To improve the dispersion of CNT in water, oxygen-containing functional groups are introduced into the surface of CNT via an acid oxidation process. The CNT-based gas sensor is fabricated by inkjet printing, which shows a high sensitivity toward NO2- The application of inkjet-printed CNT in a printed RF antenna for wireless sensing is also discussed. [ABSTRACT FROM AUTHOR]

Light-weight antenna arrays require utilizing the same antenna aperture to provide multiple functions (e.g., communications and radar) in separate frequency bands. In this paper, we present a novel antenna element design for a dual-band array, comprising interleaved printed dipoles spaced to avoid grating lobes in each band. The folded dipoles are designed to be resonant at octave-separated frequency bands (1 and 2 GHz), and inkjet-printed on photographic paper. Each dipole is gap-fed by voltage induced electromagnetically from a microstrip line on the other side of the substrate. This nested element configuration shows excellent corroboration between simulated and measured data, with 10-dB return loss bandwidth of at least 5% for each band and interchannel isolation better than 15 dB. The measured element gain is 5.3 to 7 dBi in the two bands, with cross-polarization less than -25 dBi. A large array containing 39 printed dipoles has been fabricated on paper, with each dipole individually fed to facilitate independent beam control. Measurements on the array reveal broadside gain of 12 to 17 dBi in each band with low cross-polarization. [ABSTRACT FROM PUBLISHER]

This paper demonstrates the design of an 800-MHz solar-powered active wireless beacon composed of an antenna and an integrated oscillator on a low-cost paper substrate. Inkjet printing is used to fabricate the conductive circuit traces and the folded slot antenna, while the oscillator circuit is designed using off-the-shelf components mounted on the paper substrate. Flexible, low-cost, amorphous silicon (a-Si) solar cells are placed on top of the slot ground and provide autonomous operation of the active circuit eliminating the use of a battery. A prototype is built and characterized in terms of phase noise, radiation patterns, and the effect of solar irradiance. Such low-cost flexible circuits can find significant applications as beacon generator circuits for real-time identification and position purposes, wearable biomonitoring as well as solar-to-wireless power transfer topologies. The measured phase noise is -\116 dBc/\Hz at 1-MHz offset, while drain current is 4 mA and supply voltage is 1.8 V. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) have been researched extensively for gas-sensing applications due to their unique electrical, chemical, and structural properties. Single-walled carbon nanotubes (SWNTs) have been predominantly used due to their superior electrical conductivity and higher sensitivity relative to multiwalled CNTs. This paper presents the design and characterization of a novel planar sensor fabricated on paper substrate to detect small concentrations of ammonia gas, using the shift in resonance frequency of a patch antenna as the discriminator. We have investigated three main design issues in depth. First, functionalization of the SWNTs with a polymer is studied in order to enhance the gas detection sensitivity. Second, a thin film of the functionalized SWNT is characterized to create a surface impedance model for the explanation and prediction of the resonance shift due to different gas concentrations. Finally, as a proof of concept, functionalized SWNTs are integrated into a patch antenna design and the return loss is measured in a closed-system environment to show high sensitivity for low concentrations of ammonia gas. The proposed antenna-based wireless gas sensor can be utilized in several applications, given its small form factor, light weight, and little to no power requirements. [ABSTRACT FROM AUTHOR]

For the first time, high quality factor (Q), meander inductors are demonstrated utilizing inkjet-printing on organic paper substrates. Quality factors of up to 25, which is an order of magnitude greater than previous works, and inductance values of up to 8 nH are achieved. The high self-resonance frequency (SRF) of 8 GHz makes it possible for the inductors to be used in the 900 MHz and 2.4 GHz RFID bands, and in 5 GHz Wifi band. Furthermore, a study into the performance and miniaturization effects of inkjet-printing ferromagnetic nanomaterial onto the inductors shows increases in inductance of up to 5%. Applications for inkjet printed inductors include all-printed flexible and wearable filters, resonators, and microwave matching networks. [ABSTRACT FROM PUBLISHER]

In this paper, the feasibility of inkjet printing of circuit and microwave structures on paper-based substrates is investigated for the first time in the implementation of a complete low-cost wireless platform for sensors. First, the system-level design of the module including the amplifier characterization were carried out to ensure optimum performance of the sensor modules in the UHF bands used in RF identification communication. These results were then used to design two different antenna structures, which are printed on paper along with their respective circuit layouts using inket-printing technology. Different techniques were investigated for the assembly of circuit components on the silver printed layouts. Finally, wireless link measurements on the assembled prototypes verified the good performance on the wireless and sensing sides. [ABSTRACT FROM AUTHOR]

In this paper, inkjet-printed UHF and microwave circuits fabricated on paper substrates are investigated for the first time as an approach that aims for a system-level solution for fast and ultra-low-cost mass production. First, the RF characteristics of the paper substrate are studied by using the microstrip ring resonator in order to characterize the relative permittivity (ϵτ) and loss tangent (tan δ) of the substrate at the UHF band for the first time reported. A UHF RFID tag module is then developed with the inkjet-printing technology, proving this approach could function as an enabling technology for much simpler and faster fabrication on/in paper. Simulation and well-agreed measurement results, which show very good agreement, verify a good performance of the tag module. In addition, the possibility of multilayer RF structures on a paper substrate is explored, and a multilayer patch resonator bandpass filter demonstrates the feasibility of ultra-low-cost 3-D paper-on-paper RF/wireless structures. [ABSTRACT FROM AUTHOR]

In this letter, a novel fluid-reconfigurable advanced and delayed phase line using a microfluidic composite right/left-handed (CRLH) transmission line (TL) is proposed. A CRLH-TL prototype is inkjet-printed on a photo-paper substrate. In addition, a laser-etched microfluidic channel in poly(methyl methacrylate) (PMMA) is integrated with the CRLH TL using inkjet-printed SU-8 as a bonding material. The proposed TL provides excellent phase-tuning capability that is dependent on the fluidic materials used. As the fluid is changed, the proposed TL can have negative-, zero-, and positive-phase characteristics at 900 MHz for different fluids. The performance of the TL is successfully validated using simulation and measurement results. [ABSTRACT FROM PUBLISHER]

Flexible multi-layer inkjet printed capacitors that have a self resonant frequency above 3 GHz are demonstrated for the first time utilizing two custom formulated polymer-based dielectric inks. The formulation and characterization of both dielectric inks for optimal viscosity and film thickness are performed. The frequency dependent capacitance and quality factor (Q) are presented along with a study on the repeatability and measures to improve the quality factor of printed passives. [ABSTRACT FROM PUBLISHER]

An optically transparent metamaterial absorber that can be obtained using inkjet printing technology is proposed. In order to make the metamaterial absorber optically transparent, an inkjet printer was used to fabricate a thin conductive loop pattern. The loop pattern had a width of 0.2 mm and was located on the top surface of the metamaterial absorber, and polyethylene terephthalate films were used for fabricating the substrate. An optically transparent conductive indium tin oxide film was introduced in the bottom ground plane. Therefore, the proposed metamaterial absorber was optically transparent. The metamaterial absorber was demonstrated by performing a full-wave electromagnetic simulation and measured in free space. In the simulation, the 90% absorption bandwidth ranged from 26.6 to 28.8 GHz, while the measured 90% absorption bandwidth was 26.8–28.2 GHz. Therefore, it is successfully demonstrated by electromagnetic simulation and measurement results. [ABSTRACT FROM AUTHOR]

In this paper, the far-field energy harvesting system for self-sustainable wireless autonomous sensor application is presented. The proposed autonomous sensor system consists of a wireless power supplier (active antenna) and far-field energy harvesting technology-enabled autonomous battery-less sensors. The wireless power supplier converts solar power to electromagnetic power in order to transfer power to multiple autonomous sensors wirelessly. The autonomous sensors have far-field energy harvesters which convert transmitted RF power to voltage regulated DC power to power-on the sensor system. The hybrid printing technology was chosen to build the autonomous sensors and the wireless power suppliers. Two popular hybrid electronics technologies (direct nano-particle printing and indirect copper thin film printing techniques) are discussed in detail. [ABSTRACT FROM AUTHOR]

This work introduces the material and electrical characterization of two dielectric inks for use with inkjet printing fabrication and the realization of fully-printed multilayer electronic structures. The dielectric inks are categorized by the thickness of their per-layer profiles, where SU-8 polymer and poly(4-vinylphenol)-based solutions are utilized to realize thick (>4 μm) and thin (< 400 nm) inkjet-printed dielectric films, respectively. The material formulations for each ink are outlined in detail in order to achieve the desired viscosity and surface tension for optimal printing with a Dimatix inkjet printing system. Once printability and processing techniques are tuned and established, various material and electrical characterizations are performed, including printed profile measurement, multilayer profile tendencies, thermal reflow processing, UV-ozone surface energy modification, relative permittivity extraction, leakage current density, and dielectric breakdown voltage. Finally, the demonstration of fully-printed post-processed on-chip capacitors utilizing both thin and thick dielectric inks in conjunction with a silver nanoparticle-based metallic ink is presented and compared with other inkjet-printed capacitors. [ABSTRACT FROM AUTHOR]