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Due to the effect of solution kinetics and crystallization kinetics of quantum dot (QD) during inkjet printing, the inkjet printing technique is prone to form coffee-ring patterns and in-homogenous films. Pioneering efforts are usually limited to mixed solvent or additive inks, in this paper, we investigated polymer QD films with good uniformity obtained by inkjet printing, in order to control the uniformity of quantum dot films in pixels, the mechanism of action of wettability science on inkjet printing was considered through the action of nitrous oxide (N2O) on the surfaces of substrates and banks. In the absence of N2O treatment, the inkjet-printed QD droplets would pile up and adhere to the bank walls due to capillary forces before the pinning process. With the N2O surface treatment, the contact angle of the QD ink on the substrate was increased from 16° to 62°. The wettability of the QDs between the substrate and the bank was reduced, and the side build-up phenomenon was significantly reduced. By changing the thickness of the QD film from 4.5 μm to 15 μm, the color coordinates of the spectrum were changed from (0.2320, 0.1556) to (0.1480, 0.6933).

This letter presents a microwave gas sensor based on planar coupled open loop ring resonators (OLRRs) embedded with carbon nanotube sensing film for ammonia gas sensing. The sensing area adopts the interdigitated electrode patterns to provide a larger contact area for better sensitivity. By integrating carbon nanotube films as the local variable resistors into a microwave sensor platform, the platform can transduce the gas concentration to its electromagnetic properties. According to the step response of NH3 from 100 to 1000 ppm, the sensitivity is estimated as $- 11~\mu $ dB/ppm and −232 Hz/ppm for the insertion losses and resonant frequency variations, respectively. The sensor repeatability and reversibility are also measured by maintaining the concentration from 300 to 700 ppm and repeating ten cycles with the average value of each concentration consistent with the step response. The results show a linearly response and a high repeatability of OLRRs via the real-time detection for gas sensing at high frequency and room temperature. Microwave gas sensors can be further integrated in the IoT or RF front-end system, offering low-cost, lightweight, reliable, and power efficient system for remote monitoring. [ABSTRACT FROM AUTHOR]

A study into the manufacturing considerations for developing a frequency reconfigurable antenna solution using a low-cost inkjet printing technique is presented in this article. The solution uses an off-the-shelf printer, cartridges filled with nanoparticle silver ink, and inexpensive electronic components. In this study, two conductive patches are printed on an inexpensive polyethylene terephthalate (PET) substrate, which can provide both switching and tuning by repositioning and rearranging of the components in a single-layer design configuration. The conductive silver provides an insight into the quality of the printed area. Furthermore, it provides information on potential procedures to mount and reattach the components. Inexpensive capacitors and p-i-n diodes were affixed onto the printed aperture using conductive adhesive to create complimentary dipoles for frequency reconfiguration. A single-band switching solution switches between two adjacent frequency bands. A dual-band tuning solution demonstrates dynamic tuning between a range of frequencies. Simulated and measured results are in good agreement with one another. An assortment of bands of operations allows the antennas to be suitable for mobile communication, wireless local area network (WLAN), and sensing applications. The dual-band nature of the tunable antenna can act perfectly as a bridge among 3G, 4G, and 5G communication bands. [ABSTRACT FROM AUTHOR]

Metal oxide semiconductors thin film transistors (TFTs) have become important candidates for neuromorphic computing applications by simulating the functions of biological synapses. In this article, optoelectronic synaptic transistors with tunable plasticity are achieved by utilizing printed indium tin oxide (ITO) channel and Ag/ITO dual-layer contact electrodes. The Ag/ITO dual-layer electrodes not only provide ITO TFTs with high electrical performance but enabled them with tunable plasticity. Under the synergistic electrical and optical modulation, both the short- and long-term plasticity in the printed ITO synaptic TFTs are emulated. These achievements are of great significance for applying printed synaptic transistors in optoelectronic neuromorphic hardware. [ABSTRACT FROM AUTHOR]

Delivery of electronic functionality such as sense and response to the human body using smart textiles is important for developing wearable electronics. As the key component of connecting various devices in smart textiles, electrical circuit with excellent electrical performance is an essential effort for ongoing research in textronics. In this work, a new liquid phase chemical reduction method combined with inkjet printing technology for fabricating electrical circuits on textile substrates is adopted. The aqueous silver nitrate is ejected spot by spot onto textiles that are wetted with ascorbic acid solution and placed on the copper foil. After redox and replacement reactions, silver particles are deposited to form conductive layer for electrical circuits. Deposited layers of silver with high conductivity up to ${0.86201}\times {10}^{{6}}$ S/m and the sheet resistance in the range 0.0116- $0.06913~\Omega $ /sq. Based on these findings, we realized the textile capacitive sensor with good response time, and stability for 1500 cycles of repeated loading. The fabricated textile electrocardiogram (ECG) electrode attached to braces could be effective for human heart rate and ECG signal monitoring. [ABSTRACT FROM AUTHOR]

Silicon sensors date back to before 1960 with early Hall and piezoresistive devices. These used simple processing that was part of the early integrated circuit (IC) industry. As the IC industry developed, silicon sensors could benefit from the technological advances. As silicon sensors advanced, there came the need for new technologies specifically for microsystems. This led to a range of 3-D structures using micromachining and enabled the development of both sensors and actuators. The integration of sensors with electronics on a single chip also presented new challenges to ensure that both sensor and electronics would function correctly at the end of the processing. In recent years many new technologies and new materials were introduced to enhance the functionality of microsystems. Some sensors are still based on silicon, but others introduce new materials such as carbon nanotubes and graphene. Technologies that have been used in other applications for many years are now integral part of the microsystem technology portfolio. These include screen printing and inkjet printing. Moving more into the third dimension, 3-D printing presents many new opportunities to fabricate novel structures on a silicon substrate. This tutorial focuses on the additional technologies which have been developed to supplement standard IC processes to create MEMS structures. [ABSTRACT FROM AUTHOR]

Printed and flexible sensors are in the focus of recent efforts to establish the advantages of low-cost manufacturing techniques such as screen printing or inkjet printing for printed electronical applications. Devices based on conductive carbon nanotube (CNT) networks within polymeric matrices such as polydimethylsiloxane (PDMS) are already exceeding mere technological demonstrations. Therefore, we investigate the application-oriented behaviour of fully inkjet-printed CNT/PDMS strain sensors under different conditions such as short- and long-term performance. The sensors exhibit a quasi-linear piezoresistive behaviour with vanishing hysteresis to tensile strain. Significant differences in the resistive response between compressive and tensile strain suggest complex re-orientation mechanisms of CNTs inside the matrix. No clear indication for this phenomenon could be observed in the evolution of the CNT network resistance during fatigue measurements within an uncured or cured PDMS matrix, where both scenarios exhibit no visual degradation. However, these measurements over thousands of cycles show different permanent changes in the overall device resistance exhibiting damages but also recovery in the network. Considering these findings facilitates the development of printed sensor devices.

Solution-processed devices are in general compatible with flexible and conformable electronics. However, some promising materials needs to be processed at high temperatures, which limits the applications and the use of different substrates. Among these materials we can highlight zinc oxide (ZnO), a semiconductor that stands out for transistors applications and is, in general, obtained at temperatures around 300 °C-400 °C. Here, we reported the combination of annealing at 150 °C, ultraviolet (UV) treatment and blending of ZnO nanoparticles (ZnO-NPs) with zinc nitrate and urea as a strategy to fabricate an inkjet printed electrolyte-gated transistor (EGT) with reduced temperature and improved performance, including a significant mobility improvement to 0.21 cm2/V $\cdot$ s, operating below 2 V bias, which is around 460% higher than the mobility of the EGT fabricated purely with ZnO-NPs. [ABSTRACT FROM AUTHOR]

A three-dimensional (3-D) and printed static random-access memory (SRAM) based on complementary organic thin-film transistors is demonstrated. The SRAM exhibited the smallest area of 2.1 mm2, the highest normalized static noise margin of 62%, and the maximum gain of 16.8 V/V compared to the reported values of organic SRAM cells. The transistors’ 3-D integration minimizes the cell area. The 3-D SRAM cell design enables us to match the strengths of transistors by modifying the dielectric thickness without changing the channel geometry. This high-performance complementary organic thin-film transistors-based SRAM shows its high application potential in large-scale and low-cost wearable intelligent electronics for data storage and processing. [ABSTRACT FROM AUTHOR]

A cost-effective, conformal, polarization-insensitive, light-weight, ultrathin, and ultrawideband electromagnetic wave absorber covering the entire Ku, K, and Ka bands and the lower V band is presented in this article. The absorber consists of a single layer of inkjet printed resistive metasurface laid over a flexible paper supported by a grounded foam. A novel metasurface pattern is designed by combining a checkerboard inspired symmetrical structure around a central square patch. The notable features of the proposed absorber are its ultrathin thickness of 2.17 mm (0.09 $\boldsymbol{\lambda _l}$ at the lowest operating frequency) for achieving a fractional bandwidth of 117% with a small radar cross section and its suitability for conformal applications. It exhibits more than 90% absorptivity over a frequency range from 11.87 to 45.28 GHz for all the angles of polarization and is also angularly stable. The theoretical, simulation, circuital, and experimental analysis validates the various features exhibited by the absorber. [ABSTRACT FROM AUTHOR]

Flexible printed electronic technology makes it possible to fabricate low-cost digital microfluidic (DMF) chips. Inkjet printing on flexible substrates is one of the most cost-effective fabrication processes for DMF chips. Based on inkjet printing technology and simplified coating methods of dielectric and hydrophobic layers, we fabricated low-cost flexible DMF chips (FDMFCs) on PET sheet and on matte photo paper. The surface quality, conductivity and spatial output resolution of the silver lines under different number of printings, different line widths and line gaps on the two types of FDMFCs were comprehensively analyzed. The traditional square dispensing electrodes were optimized to reduce the volume error of the droplets generated during the repeated dispensing operations. Droplets can be driven to implement all the operations on various configurations of FDMFCs by electrowetting-on-dielectric, including closed configuration, open configuration, hybrid configuration composed of closed and open regions on a single chip, and open curved configuration, which are defined as full-range droplet actuation. The droplet motion between closed and open regions in two position modes of the top plate was deeply studied. Droplet operation experiments prove that the motion performance of droplets can be comparable to that of chips processed by traditional technology, and the rapid prototyping technology of the FDMFCs can make the performance of droplet operation mainly depend on the conductivity of the electrode layer and the electrode gap and greatly weaken the influence of the substrate surface quality on the FDMFCs. [ABSTRACT FROM AUTHOR]

Usually, the printed circuit board industry has to use special subtractive manufacturing methods, if small line and space dimensions down to 50 μm are desired. This drastically raises production effort and costs. In this article, a method is shown as to how the inkjet technology can be used to produce passive RF structures with minimum line and space dimensions of 25 μm. For the first time, this is possible over complete panels of low-cost printed circuit board (PCB) substrates, which have a relatively high surface roughness compared to ceramic or glass carriers. To ensure process reliability, printed lines must also be plated with an additional electroless copper layer to overcome the surface roughness with conductive layers and to lower insertion loss in the two-digit GHz range. Additionally, a surface impedance model is developed, which allows broadband first time right simulations. Finally, additively produced, passive RF filters are compared to their subtractive counterparts to show their benefits regarding production costs and electrical performance up to 80 GHz. [ABSTRACT FROM AUTHOR]

The objective of this article is to devise a cost-effective, conformal, polarization-insensitive, and broadband metamaterial absorber for X-band applications. A periodic subwavelength conducting grid pattern is printed over flexible papers in a multi-layered fashion to achieve the broadband behavior. A silver nanoparticle incorporated inkjet printing technique is employed that does not require any post-processing such as sintering. The absorber is eco-friendly and suitable for rapid mass production at a low-cost. Moreover, the printed patterns do not crack when bent or applied over curved surfaces. The characteristics, working principle, and equivalent circuit of the absorber are described. The absorber is designed on a 1.06 mm (0.03 λl at the lowest working frequency) ultrathin substrate. It exhibits more than 90% absorptivity from 8.43 to 10.38 GHz for all angles of polarization with wide angular stability up to 45°. The flexibility and broadband feature is also confirmed by the experimental measurement of the fabricated prototype. [ABSTRACT FROM AUTHOR]

The development of soft electronics is critical to the realization of artificial intelligence that comes into direct contact with humans, such as wearable devices, and robotics. Furthermore, rapid prototyping and inexpensive processes are essential for the development of these applications. We demonstrate here an additive, low-cost method for fabricating polydimethylsiloxane based soft electronics by inkjet printing. Herein, a novel approach using a water-soluble polyvinyl alcohol layer as the substrate, inexpensive, fully digital fabrication of capacitive pressure sensors is enabled by sandwiching mesh-like conductive layers and microstructured dielectric in a straightforward, convenient manner. These sensors exhibit improved sensitivity (4 MPa−1) at low pressures (< 1 kPa) in contrast to sensors with a flat elastomer dielectric and can still detect large pressures around 50 kPa, having excellent long-term repeatability over 2000 cycles, without significant hysteresis (≤ 8.5 %). The tactile sensing ability of the fabricated devices was demonstrated in a practical application. Moreover, sensor characteristics are easily adjustable, simply by changing printing parameters or tuning the ink solution. The proposed approach provides scalable solution for fabricating high-sensitivity printed sensors for e-skin and human-machine interfaces. [ABSTRACT FROM AUTHOR]

We present a method for printing conductive polymers onto P(VDF-TrFE) nanofibers to create all-polymer piezoelectric devices. Inkjet printing is an attractive fabrication approach for rapid prototyping of flexible electronics, but until now with limited applications in developing P(VDF-TrFE) nanofiber-based devices. We have demonstrated an approach to infill the void space within a piezoelectric nanofibrous matrix to allow for the inkjet printing of aqueous inks while avoiding leakage that typically leads to electrical shorting and without significant loss of voltage output. This was done using a diluted PDMS solution and a commercially available conductive ink. The 1 cm2 devices showed a 254 mV/N sensitivity to impact as well as a sensitivity to bending. The device was shown to be able to detect breathing and pulse rate when placed superficially to the carotid and radial arteries. Using these techniques, flexible piezoelectric sensing can be done in an array format, shown with applications in foot movement sensing. [ABSTRACT FROM AUTHOR]

The successful development of biosensors is a result of a combination of technological achievements from various disciplines. A prerequisite for the creation of a successful biosensor is the placement of the biomolecules in specific locations with high resolution, on the sensor substrate, and the immobilization of the biomolecules with techniques that are able to ensure the bioactivity of the biomaterials while at the same time guarantee their attachment to the sensor surface for a desirable period of time. Furthermore, the future of biosensors depicts the need of development of new generation of biosensors with improved performance, increased sensitivity and selectivity while being able to monitor the results in real time and detect multiple analytes with the same sensor simultaneously. To satisfy those high expectations, the scientific community develops techniques to improve the electronic part and the signal of the biosensor device while also various techniques are investigated for the digital printing and functionalization of the sensor surface with the bio materials. To this end, this review tutorial focuses on direct write bioprinting techniques that have been used extensively for the printing of the biomaterials on various type of surfaces including sensor devices. We review the recent advancements of the techniques, in the field of biosensor development and explore their potential to be used for the creation of an all printed device rather than techniques used only for spotting biomaterials. Such advancements are expected to expand the biosensor availability and lower the cost while having a high impact to multiple disciplines. [ABSTRACT FROM AUTHOR]

This paper presents a versatile and precise graphene patterning technique using the combined process of masking and inkjet printing. A graphene-based structure is fabricated by first defining the structural pattern and position using a masking mold, which can be either electroplated copper or deep reactive ion etching (DRIE) silicon shadow mask, followed by inkjet deposition of graphene ink and lift-off. The hybrid technique can realize high-fidelity, high-resolution graphene-based microstructures including free-standing and cantilever beams, four-point resistive measurement structures, and piezoresistive sensing elements with a minimum line width of $\sim 20~\mu \text{m}$ . Moreover, this method can facilitate the micropatterning of graphene oxide (GO) and reduced graphene oxide (rGO) on substrates such as polydimethylsiloxane (PDMS) and SiO2/Si for selective cell culturing applications. Owing to the characteristics of low chemical usage, low process temperature and complexity, and high flexibility and fault tolerance of inkjet printing, this technique demonstrates compelling potential for a variety of biomedical applications.

An investigation on antenna solutions for expendable origami paper flapping robots is presented. An origami flapping robotic bird that can be produced using standard A4 paper is employed. Antennas resonating at the two commonly used frequency bands, 2.4 GHz and 5.2 GHz, are designed for the limited space available on the folded origami structure. Two developments of the same dual-band monopole antenna are discussed. The first antenna is located on the robot's spine and the second on its tail. A space diversity configuration is also studied. The antennas are printed directly onto a photo paper substrate and then folded into an origami robotic crane's body structure. An ordinary desktop inkjet printer fitted with silver nanoparticle conductive ink cartridges has been employed. CST Microwave StudioTM has been used to design the antennas. A good agreement between the measured and simulated S11 results is achieved with a reasonable -10dB impedance bandwidth realized in the three cases studied. The radiation patterns are omnidirectional in the XZ plane which is desirable for the specific application. The diversity configuration has a mutual coupling of

In this article, a novel methodology to tune parameters of a resonant accelerometer realized by a flexible structure is presented. A model describing the behavior of the tuning mechanism has been proposed and experimentally validated as well as a suitable design flow is presented through case studies. The device under test, whose dimensions are in the mesoscale, adopts a resistive sensing readout strategy implemented through strain gauges, directly inkjet printed on the flexures (springs) supporting the central membrane. The tuning mechanism, which exploits the interaction between an external magnetic field and a magnetic fluid (ferrofluid) embedded in the device’s springs, has been experimentally investigated by using a lab-scale prototype. The procedure for the optimal design of the sensor has also been addressed. The prototype shows a responsivity of 721.0 $\mu $ strain/m/s2 at the resonance frequency of 30.5 Hz and a noise floor of 7.5e $- 5 { \text {m/}}\text {s}^{{2}} {/}\sqrt {\text {Hz}} $ estimated in a bandwidth of 500 Hz. Responsivities of $657.0~\mu $ strain/m/s2 and $580.0~\mu $ strain/m/s2 as well as noise floor of 8.7e $- 5 { \text {m/}}\text {s}^{{2}} {/}\sqrt {\text {Hz}} $ and 10.9e $- 5 { \text {m/}}\text {s}^{{2}} {/}\sqrt {\text {Hz}} $ have been estimated in case of the tuning magnetic fields of $H =6.8\text{e}-3$ T and $H =11.4\text{e}-3$ T, respectively, showing resonance frequencies of 31.0 and 32.5 Hz. The main novelty of the proposed approach arises from the tuning strategy that is important for many real applications requiring a fine-tuning of the sensor parameters while the use of a cheap inkjet printing technology for the device realization represents a substantial advantage in terms of costs and to enable the rapid prototyping of customizable devices on flexible substrates. [ABSTRACT FROM AUTHOR]

The presented work focused on the development of temperature sensors based on specially formulated carbon nanotube (CNT) and poly(3,4-ethylene dioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) based inks which are deposited directly onto the adhesive polyamide-based taffeta fabric with low-cost office-type inkjet printer. Stable and uniform dispersions of CNT and PEDOT:PSS with Triton X-100 were formulated to be used as temperature sensitive inkjet inks. Three kinds of temperature sensors were fabricated using sensitive materials including CNT ink, PEDOT:PSS ink, and CNT/PEDOT:PSS composite ink. Developed sensors are connected to the measuring devices via silver yarns and silver adhesive paste. Sensors are covered with translucent polyurethane welding tape for packaging and protection. All the sensors exhibit negative temperature coefficient (NTC) behavior and sensitivity of 0.15 %/°C for CNT, 0.41 %/°C for PEDOT:PSS, and 0.31 %/°C for CNT/PEDOT:PSS for temperatures varying from room temperature to 50 °C. CNT/PEDOT:PSS composite ink printed sensor achieved better sensing repeatability and demonstrated higher bending stability with a resistance change of 0.3 % up to 1000 cycles than CNT printed and PEDOT:PSS printed sensors. The softness, lightness, and capability to work on flexible or curved surfaces make the developed CNT/PEDOT:PSS composite ink printed sensor a robust candidate for wearable temperature sensor applications, especially in situations requiring continuous body temperature monitoring while satisfying comfort of the user. [ABSTRACT FROM AUTHOR]

Porous-matrix composites comprising single-walled carbon nanotubes (SWCNTs) with bound magnetic nanoparticles (NPs) as filler are interesting multifunctional materials whose electrical and magnetic parameters can be used as hallmarks for identification of a genuine document or a bank note, for example. We have formulated stable functional ink based on commercially available product composed of SWCNTs (76 wt. %) and iron-based NPs (11 wt. %) and deposited them on four different thin sheet materials at a given dosage with the use of specialized inkjet printer. To study the magnetic properties, a high-Tc superconducting quantum interference device (HTS SQUID) was designed and fabricated. The printed samples were magnetized in the weak dc magnetic field (3.0 mT/μ0) and moved in the direction of applied field in close proximity to a SQUID sensor. It was found that peak-to-peak stray magnetic field of a magnetized sample (being proportional to its average magnetization) depends on the type of sheet material on which the ink was printed. The larger is the thickness of the printed layer comprising SWCNTs with magnetic NPs, the lower is the signal. Since iron-based NPs are superparamagnetic due to their small size (mean size ∼ 4 nm), the difference in the magnetization may result from the difference in the contribution of exchange interaction between NPs. The performed calculations demonstrated that the decay length of electron wave function characteristic of the magnetization is about seven times larger than that of the hopping conductivity in the composites, thus suggesting the mechanism of indirect exchange interaction between NPs involving SWCNTs. [ABSTRACT FROM AUTHOR]

This article compares the thermomechanical behavior of 3-D inkjet-printed microelectronics devices relative to those fabricated from traditional methods. It discusses the benefits and challenges in the adoption of additive manufacturing methods for microelectronics manufacture relative to conventional approaches. The critical issues related to the design and reliability of additively manufactured parts and systems stem from the change in the manufacturing process and the change in materials utilized. This study uses numerical modeling techniques to gain insight into these issues. This article is an extension of the same topic presented at the 2018 IEEE Electronics Packaging Technology Conference. An introduction providing an overview of the area, covering salient academic research activities and discussing progress toward commercialization is presented. The state-of-the-art modular microelectronics fabrication system developed within the EU NextFactory project is introduced. This system has been used to manufacture several test samples, which were assessed both experimentally and numerically. A full series of JEDEC tests showed that the samples were reliable, successfully passing all tests. The numerical model assessing the mechanical behavior of an inkjet-printed structure during layer-by-layer fabrication is presented. This analysis predicts that the stresses induced by the UV cure process are concentrated toward the extremities of the part and, in particular, in the lower layers which are constrained by the print platform. Subsequently, a model of a multilayer microelectronics structure undergoing JEDEC thermal cycling is presented. The model assesses the differences in mechanical properties between a conventional FR4/copper structure and an inkjet-printed acrylic/silver structure. The model identified that the influence of the sintering process on subsequent material properties, behavior of the inject-printed structure, and reliability of the inject-printed structure is significant. Key findings are that while stresses in the conventional and inkjet boards are relatively similar, the inkjet-printed board exhibits significantly greater deformation than the standard board. Furthermore, the mechanical stresses in the inkjet fabricated board are strongly dependent on the elastic modulus of the sintered silver material, which, in turn, is dependent on the sintering process. [ABSTRACT FROM AUTHOR]

The color converting film (CCF) is first fabricated by the inkjet printing technology with the drop-on-demand advantage in the paper, the volume ratio of the red quantum-dots (QDs) over green QDs is 1:12.9 at balanced intensity, and each subpixel of the CCF is sprayed with five droplets with each volume of 48 pL. The CCF has been equipped in the corresponding liquid crystal display (LCD) module. In theory, the optical efficiency of the CCF mainly depends on the quantum yield of QDs, therefore, and the total optical efficiency can improve by 2.4 times. The LCD module sample has been tested to verify the performance. Experimental results show that the color gamut reaches 131.4% NTSC in CIE 1931, the total optical efficiency is 20%. Comparing with the wide color gamut backlight module with QDEF, the color gamut improves by 16.4% NTSC, the total optical efficiency improves by 2.1 times, and the average color crosstalk ratio decreases by 4.21% under the condition that the misaligned size is larger than the width of the black matrix. Our method provides theoretical guidance to realize high-performance LCDs.

Neural damage caused by reactive oxygen species (ROS) can trigger several acute or chronic conditions, such as Alzheimer's, Huntington's, and Parkinson's diseases. However, ROS scavengers hold great promise for enabling DNA repair in neurons; damaged cells using ROS-scavenging agents may be able to recover their functionality and resilience. Moreover, in bioelectronics for neural applications, thin films with adequate properties are crucial for the proper performance of an electronic device. Therefore, precise and reliable deposition techniques that can control the characteristics of thin films are imperative when fabricating bioelectronic devices integrated with cellular systems. To that end, inkjet printing is a promising method with unique advantages, such as computer-assisted protocols and efficient consumption of materials. We report the printing of a functional electronic material that exhibits ROS scavenging behavior (Manganese [III] 5, 10, 15, 20-tetra [4-pyridyl]-21H, 23H-porphine chloride tetrakis [methochloride]) using a modified inkjet printer. Different printed pattern schemes that were designed based on the amount of overlap among sequential droplets were used to tune the surface morphology of the inkjet-printed thin films with a wide range of roughness (8.84-41.20 nm). Furthermore, post-printing processes (such as plasma treatment) were used to optimize surface energy. Such inkjet printing methods of functional electronic materials that can simultaneously be used as ROS scavengers, would advance bioelectronics applications in neural studies.

Thermal sintering has traditionally been the most popular sintering method to enhance conductivity after the printing process in the manufacturing of printed electronics. Nevertheless, in recent years, there has been a growing interest in electrical sintering as an alternative method to overcome some of the limitations of thermal curing. This paper makes a comparative study of both sintering methods in terms of surface morphology, electrical dc conductance, and radiofrequency performance for different applied voltage waveforms. To this end, microstrip transmission lines have been inkjet-printed using nanoparticle-based silver ink on flexible polyimide substrate. The traces have been tested under different sintering conditions, achieving electrical sintering resistivity values only 2.3 times higher than that of bulk silver. This implies a 62% reduction in comparison with the best resistivity value achieved using thermal sintering in our samples. The main novelty of this contribution lies in the analysis of RF behavior as a function of electrical sintering conditions. Lower resistivities have been achieved with slower voltage ramps or allowing higher density current during sintering. It has also been proved that electrically sintered lines have similar RF performance than high-temperature thermally sintered lines in terms of insertion losses, regardless of their very different surface topology. Therefore, we can take advantage of the benefits that electrical sintering offers over thermal sintering regarding significant shorter sintering times maintaining suitable RF performance.

This paper presents an all-printed human body temperature sensor developed on a plastic substrate with high deformation characteristics. The sensors are developed on $50~\mu \text{m}$ thick Kapton substrate with structural configuration of silver interdigital electrodes (IDEs) fabricated through inkjet material printer DMP 2850 and the sensing film based on carbon black deposited through doctor blade coating. Interdigital distance of the IDEs were optimized by evaluating sensors’ performance against changing the fingers spacing within a close range of 0.1–1 mm. Good sensitivity i.e. 0.00375 °C−1 is achieved at a temperature range of 28 to 50 °C with response and recovery times of 4 and 8.5 sec, respectively. Robustness of the sensor was also evaluated for a period of 50 days and a negligible drift ( $1\Omega$ ) in the base resistance was recorded. The sensor exhibited bendability down to 5 mm and was also characterized for the chemical and electrical properties i.e. resistance variation, surface morphology and Raman shift analysis of the carbon black. This wearable sensor can potentially be applied on human body for continuous temperature monitoring as well as on the artificial skin for social and industrial robotic applications.

This paper presents an energy-efficient mm-scale self-contained bidirectional optogenetic neuro-stimulator, which employs a novel highly-linear $\mu$ LED driving circuit architecture as well as inkjet-printed custom-designed optical $\mu$ lenses for light directivity enhancement. The proposed current-mode $\mu$ LED driver performs linear control of optical stimulation for the entire target range ($< $ 10 mA) while requiring the smallest reported headroom, yielding a significant boost in the energy conversion efficiency. A 30.46× improvement in the power delivery efficiency to the target tissue is achieved by employing a pair of printed optical $\mu$ lenses. The fabricated SoC also integrates two recording channels for LFP recording and digitization, as well as power management blocks. A micro-coil is also embedded on the chip to receive inductive power and our experimental results show a PTE of 2.24 $\%$ for the wireless link. The self-contained system including the $\mu$ LEDs, $\mu$ lenses and the capacitors required by the power management blocks is sized 6 mm $^3$ and weighs 12.5 mg. Full experimental measurement results for electrical and optical circuitry as well as in vitro measurement results are reported. [ABSTRACT FROM AUTHOR]

The significant incidence of cancer on public health in the modern industrialized world is pushing the research on novel therapeutic techniques and diagnosis tools. The latter, in particular, are of vital importance, since in many cases a prompt cancer diagnosis can significantly decrease patient’s mortality. Bioimpedance tissue analysis, in particular, is gaining attention as a promising methodology to identify tumor. Manufacturing technologies for bioimpedance probes are however still not completely adapt for cost effective mass production. In this context, the present work aims at producing a costless bioimpedance sensor by employing inkjet printing and electrolytic metal deposition. The probe manufactured in this way is successfully employed for bioimpedance testing of three animal tissues, demonstrating ability to successfully distinguish between them. [ABSTRACT FROM AUTHOR]

Rectifiers are vital electronic circuits for signal and power conversion in various smart sensor applications. The ability to process low input voltage levels, for example, from vibrational energy harvesters is a major challenge with existing passive rectifiers in printed electronics, stemming mainly from the built-in potential of the diode’s p-n-junction. To address this problem, in this work, we design, fabricate, and characterize an inkjet-printed full-wave rectifier using diode-connected electrolyte-gated thin-film transistors (EGTs). Using both experimental and simulation approaches, we investigate how the rectifier can benefit from the near-zero threshold voltage of transistors, which can be enabled by proper channel geometry setting in EGT technology. The presented circuit can be operated at 1-V input voltage, featuring a remarkably small voltage loss of 140mV and a cutoff frequency of ~300 Hz. Below the cutoff frequency, more than 2.6-μW dc power is obtained over the load resistances ranging from 5 to 20 k Ω. Furthermore, experiments show that the circuit can work with an input amplitude down to 500mV. This feature makes the presented design highly suitable for a variety of energy-harvesting applications. [ABSTRACT FROM AUTHOR]

Printed sensors that rely on low-cost substrate materials and additive fabrication processes are needed for wearable and disposable device applications. A critical challenge associated with currently available printed sensors is their inferior performance compared with sensors fabricated by thin-film deposition or nanoscale assembly. In this paper, we report on an inkjet-printed hydrogen peroxide (H2O2) sensor possessing a sensitivity >30X higher than those made by conventional sputtering. The key enabling step in our printing approach is low-temperature plasma conversion of an inorganic salt precursor to produce silver (Ag). The resistivity of the printed Ag measured by four-point probe is found to be only 6X higher than that of bulk Ag and 5X higher than that of sputtered Ag. Additionally, the surface roughness of the printed Ag characterized by optical profilometry and atomic force microscopy is much higher than that of the sputter-deposited Ag. The resulting large surface area of the printed Ag leads to a significantly improved reaction rate with H2O2, and is responsible for the increased sensitivity of the sensor. [ABSTRACT FROM AUTHOR]

During usage, printed electronic components are often stretched, bent, folded, and/or twisted to conform to underlying structure. In this article, tests have been developed for characterizing the mechanical and high-frequency electrical behavior of inkjet-printed patch antennas on flexible polyethylene terephthalate (PET) substrates under uniaxial and biaxial bending. A patch antenna is designed to have a single resonant frequency of 5 GHz in free space. Polycarbonate cylindrical mandrels of 1.25” diameter and special sculptured surfaces have been used as uniaxial and biaxial bending fixtures, respectively. Up to 2000 bending cycles have been performed in both uniaxial and biaxial bending tests. During bending tests, $S_{11}$ (return loss) has been measured by a vector network analyzer (VNA) in both bent and flat configurations. Mechanical simulations have also been performed to determine the strain distribution in the printed elements which will lead to changes in electrical behavior. Scanning electron microscope (SEM) images have been taken to examine the physical damage in the printed structure and to correlate with the strain values obtained through mechanical simulation. High-frequency electrical simulations have also been performed to correlate with the bending experimental data. It is seen that the conductivity of the printed structure changes differently in different zones, due to various values of strain they undergo. Although the cracks are observed in the printed structures, the maximum relative shift in the measured resonant frequency is less than 1.66% in both uniaxial and biaxial bend tests. [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]

A high-level (i.e., in terms of security) authentication method is proposed in this communication, where the chipless RFID is extended to the chipless authentication. The proposed method is based on low-cost inkjet-printed square-check-patterned chipless tags, whose design is explicitly optimized keeping the randomness inherent to the inkjet-printing process in view. These optimized chipless tags are very difficult to duplicate, as their unique backscattered EM responses depend on proximate coupling among the possible separated squares that happened naturally due to the randomness of inkjet printing. The performance of the proposed method is analyzed by a low-cost impulse radio (IR) UWB chipless RFID reader as well as by the highly accurate VNA-based chipless RFID reader. The achieved probability of error is comparable to the various fingerprint evaluation campaigns found in the literature. [ABSTRACT FROM AUTHOR]

In this letter, we demonstrate a fully inkjet-printed electrochemical lactate sensor. The sensor is inkjet-printed on a flexible substrate, Kapton film, where silver nanoparticles (Ag NPs) are printed as conductive electrodes. The working and reference electrodes of the sensor are Ag NPs/NiO NPs/Polyurethane (PU) and Ag/AgCl(s)/PU layers respectively. The inkjet-printed PU film can not only prevent the annihilation of the Ag NPs resulting from the dissolution of Ag and the formation of AgCl in the phosphate-buffered saline (PBS) but also stabilize the lactic acid measurements by maintaining a potential variant within 2% at different lactate concentrations. The as-printed sensor exhibits a linear sensitivity of 8.86nA/mM/mm2 (R=99.6%) in the range from 0.6 to 2.2 mM. Clinical blood plasma testing results show that the trends of lactic acid change in patients measured by the sensor are the same as the ones measured using the existing detection method, colorimetric assays, in a tertiary university-affiliated hospital. [ABSTRACT FROM AUTHOR]

We report the fabrication of low voltage dual-gate organic thin film transistors, and their possible applications for PMOS inverters and NOR logic gates, on $125~\mu \text{m}$ -thick flexible polyethylene naphthalate (PEN) substrates using solution-processed techniques. Source, drain, and gate electrodes are made by inkjet-printing, while active semiconductor is printed by a dispenser system over parylene dielectric. Bottom and top channel interfaces have been characterized by taking long drain current transients. Formation of stable top channel interface, with low trap density, is a reason for higher top channel current than bottom channel. Increase in drain current transients, and positive threshold voltage shift is attributed to the accumulation of extra positive charge carriers induced by slow polarization of the dipoles in the parylene dielectric. [ABSTRACT FROM AUTHOR]

Digital printing technologies, such as inkjet or aerosol jet, are becoming increasingly interesting for the manufacturing of electronic devices. As a maskless and contactless process, it offers the potential for low-cost deposition of functional materials onto flat, flexible, or 3-D substrates. Common inks used for printed electronics are nanoparticle (NP) metal inks. Silver (Ag) is widely used because of its excellent conductivity, but also gold (Au) inks are of interest for several applications. By using NP inks, it is possible to integrate conductive paths and sensors onto temperature-sensitive substrate materials, such as polymers. Polymers often need a pretreatment, such as a plasma treatment for improving the wetting. Plasma treatment usually changes the wetting behavior of the complete substrate surface. This could be critical for some applications, e.g., fluidic applications, where the original properties of the substrate should be kept. Low-pressure plasma as a vacuum process is also difficult for implementation into an existing process. In this article, laser irradiation for local improvement in wetting of an inkjet-printed gold ink on polymer substrates is investigated. The experiments show that laser irradiation is a very promising technique for the modification of polymer surfaces and suitable for inkjet printing NP inks on hydrophobic polymer surfaces. This offers new opportunities for printed electronics, which could be easily integrated into the existing processes. [ABSTRACT FROM AUTHOR]

Hydrogen-terminated diamond gas sensors have been prepared by selective deposition of nanodiamond ink using direct inkjet printing on interdigital electrodes, followed by chemical vapor deposition growth of a nanoctrystalline diamond layer. The structure of the deposited layer was characterised and analyzed by scanning electron microscopy and Raman spectroscopy. The effect of ultraviolet light-emitting diode (UV-LED) illumination on the performance of the hydrogen-terminated diamond gas sensor with regard to reducing (NH3) and oxidizing (NO2) gases at various temperatures was studied. UV-LED illumination showed a short response/recovery time to NH3 and NO2 gases, 97 s/153 s, and 72 s/186 s, respectively. [ABSTRACT FROM AUTHOR]

In this paper, an additive method to make electrical contacts in SOI MEMS devices with aerosol jet printing is introduced. Small grooves were etched to the frame of MEMS accelerometer in the same step with the active structure release. Aluminum ink was jetted to the trenches in wafer-level to bridge the device layer to the handle wafer with the minimum amount of material. After subsequent annealing, ohmic contacts between p-type device layer and p-type handle silicon were verified by I-V measurements. The via resistance less than 4 Ω per via is measured. The method demonstrated in this paper provides simple and low-cost approach for SOI handle contact where additional packaging of wafer process steps can be avoided.

A flexible and low profile frequency selective surface (FSS) with bandstop behavior for X-band signals is demonstrated in this paper to support the demand of the flexible wireless communication devices in the today's market. The resonating element of the FSS is realized using the convoluted ring loop element that is inspired by the conventional ring loop element. An additional of four stubs are added at each 90° of the conventional ring loop to miniaturize its overall dimension. The convoluted ring loop FSS has reduced the overall dimension of the conventional ring shape FSS to 0.25 λ0 with a reduction of 33%. The proposed FSS is developing by utilizing the flexible polyethylene terephthalate substrate with the measured thickness of 0.125 mm and dielectric constant of 2.7. From the simulated transmission response of the FSS, it shows that the proposed convoluted ring loop FSS with planar feature manages to provide a signal attenuation up to 37 dB at 10 GHz for both normal and oblique angle of incidence up to 45° at TE and TM polarization. For validation purpose, the prototype of the FSS is manufactured using the inkjet printing technique. The FSS is bent in a different manner, such as bending the array FSS with different radius and bending the unit cell convoluted ring FSS row by row, to examine the bending effect toward the transmission response performance. All the simulated results are compared with the measured results, and these results are in concurrence with each other. By having the conformal features, the employability of the FSS is enhanced whereby the proposed flexible FSS can be employed as the sub-reflector for wearable antenna and conformal shields for electromagnetic compatibility applications.

Inkjet printing is a non-vacuum, non-contact, low-cost, and direct patterning thin film deposition technique. Compared to traditional processes, it demands less materials and energy, simplifies processing steps and is compatible with the fast fabrication of flexible and large-size devices, thus potential in the application of thin film transistors. In this paper, we have compared the main techniques of inkjet printing, and discussed the formulation of conductive inks, the deposition of high quality electrodes, and the obtaining of high resolution and high performance thin film transistors. Moreover, the faced problems and corresponding solving methods of inkjet printed thin film transistor with low sintering temperature, small line width, short channel, high mobility, and designed structure are summarized by the understanding of the interaction among inkjet printing devices, materials, processes, and the fabrication of transistors, which providing referential significance of the following research effort.

In the last several years, conventional drug delivery systems (DDS) have evolved into DDS that are responsive to exogenous or endogenous stimuli. The objective of this paper is to present a DDS that is responsive to an electric stimulus in the form of bipolar electric pulses. The DDS structure is based on chitosan embedded with magnetic nanoparticles, and crosslinked with polyethylene glycol dimethacrylate to form microbeads. This DDS is loaded with vancomycin as the therapeutic agent of interest. Silver inter-digitated electrodes (IDE) were printed on polyimide substrates with a MEMS-based inkjet material deposition printer, and used to provide 100 Hz pulses of electric current to the DDS for 3 min. The results showed that the stimulated groups released ∼800% more vancomycin than the non-stimulated groups in the excitation duration, but followed a first-order elution profile otherwise. Another significance of our approach is that it does not need complicated or expensive fabrication processes, and can be customized according to the targeted implant site. The IDE system has also been modeled using COMSOL to study the distributed electric fields and ion migration during the stimulus. This paper demonstrates a novel and promising technique of providing stimulus to drug substrates for controllable drug delivery. [ABSTRACT FROM AUTHOR]

Numerous medical operations employ blood transfusions, requiring X-ray irradiated blood for safety concerns. Current irradiation techniques can be significantly improved by replacing standard visual indicators with wireless dosimeter tags that automate the process, reducing inefficiencies, and eliminating blood wastage. A key requirement of the proposed dosimeter tag is flexible and efficient antennas that can be mounted on blood bags. This paper presents the design of a low-cost inkjet-printed dipole antenna on flexible Kapton substrate for a 2.45 GHz radio frequency identification (RFID) dosimeter tag. The tag is to be used in a lossy blood environment, which can severely affect antenna radiation performance. To mitigate this, the concept of artificial magnetic conductor (AMC) unit cells is investigated for best impedance and gain performance. When integrated with a dipole radiator, the fabricated AMC-backed antenna maintains broadside radiation with gains of 4.1–4.8 dBi under planar and bending conditions, and on a lossy blood bag. In a rectenna configuration, the antenna can power sensors for ranges up to 1 m. Measured output dc voltages up to 1.7 V are achieved across a 25 $\text{k}\Omega $ resistor. This antenna design is flexible, compact, efficient on lossy structures, and suitable for direct integration with biomedical sensing chips. [ABSTRACT FROM AUTHOR]

A dual-gate configuration has been introduced to organic thin-film transistors (TFTs) for full-depletion behavior to enhance the transconductance, subthreshold slope, and drain current on–off ratio. In this letter, we show how those dual-gate effects influence the static and dynamic responses of three-dimensional (3-D) complementary organic logic gates in comparison to their single-gate counterpart. For the comparative study, 3-D inverters and ring oscillators were fabricated by printing directly on plastic foil in both single- and dual-gate configurations. In the static inverter operation, the fully depleted characteristics of the dual-gate TFTs lead to an increase in voltage gain and a dramatic decrease in standby power consumption. In the dynamic ring oscillator operation, the two configurations have comparable gate delays because the use of an additional gate increases not only the drain current but also the load input gate capacitance. Our findings demonstrate the performance of an inverter that can represent the overall operation of complementary logic gates consisting of pull-up and pull-down networks, thereby providing significant insight into the printed organic TFT circuit design using dual gating effects. [ABSTRACT FROM AUTHOR]

The single- and double-layered photodetectors based on ZnO and/or detonation nanodiamond (DND) have been developed via a sequential inkjet printing on the interdigital electrode platform using a diamond and zinc oxide precursor ink. The morphological structure of the deposited materials was visualized and analyzed by scanning electron microscopy and atomic force microscopy. The crystalline configuration and structural quality of ZnO and nanodiamond were investigated by X-ray diffraction and Raman spectroscopy. The response, response time, and recovery time were measured for different UV wavelengths (365, 385, and 405 nm), light intensities, temperatures, and bias voltages. The ZnO/DND structure shows more than ten times higher response and faster reactivity in comparison with a single-layered photodetector. Photoresponsivity of the double-layered photodetector (ZnO/DND) is 0.35 A $\cdot \,\,\text{W}^{ {-1}}$ , whereas bare ZnO is about 0.039 A $\cdot \,\,\text{W}^{{-1}}$. The interaction between UV light and ZnO/DND grains was investigated by two dimensional Silvaco TCAD simulation. [ABSTRACT FROM AUTHOR]

Photodetectors (PDs) based on organic–inorganic hybrid materials such as graphene and perovskites have recently emerged at the forefront of the research in optoelectronic devices. Despite the remarkable progress in the performance of optoelectronic devices based on hybrid materials, some aspects such as stability have so far not been thoroughly addressed. This paper serves to demonstrate a fully inkjet-printed PD fabricated by hybrid perovskite (CH3NH3PbClx-3I3) layer between the two graphene electrodes as graphene/perovskite/graphene (GPG) heterostructure. The fully inkjet-printed GPG PD is found to be effective for the visible light region, which can be attributed by the high uniformity and low defects of the printed materials. Thus, the GPG PD achieves a high responsivity of 0.53 A/W. Fully inkjet-printed hybrid perovskite PD demonstrated in this paper unveils the facile, potentially large-scale and cost-effective methods for fabrication of hybrid perovskites-based optoelectronic devices, including PDs and solar cells. [ABSTRACT FROM AUTHOR]

This paper presents an inkjet-printed differential passive microwave planar resonator-based sensor for toxic vapor detection at room temperature. Two devices are presented, with 5 (D1) and 50 (D2) layers of composite sensitive film (PEDOT:PSS-MWCNTs). Each one consists of two band-pass resonators with the fundamental modes around 2.5 and 2.7 GHz. Theoretical and experimental results are presented, both devices show sensitivity to ethanol vapor ranging from 500 to 1300 ppm according to the magnitude and resonant frequency shifts of their scattering parameters (S-parameters). Limitations due to a continuous drift on both the reference and the sensitive channels are discussed. Though further improvements are needed, such sensor is a good candidate for integration into real-time multi-sensing platforms adaptable for the Internet of Things. [ABSTRACT FROM AUTHOR]

This paper proposes a new inkjet printing system based on the electrohydrodynamic (EHD) method, and its performances are experimentally evaluated using the copper nano-sized particles ink. After briefly explaining the working principle of the proposed printing system, both static and dynamic characteristics of the frame structures are investigated to ensure structural stability. Then, principal components such as the laser sensor are calibrated to reduce the printing position error. Subsequently, the metal inks featuring the copper particles are prepared using both the ultrasonic homogenizer and the planetary centrifugal mixer to make homogeneously dispersed state. It is shown that the printing results are excellent with proper operating conditions of the operating frequency up to 500 Hz. The superiority of the proposed system is demonstrated through evaluations of the printing resolution and measurements of width and thickness of the printed line. [ABSTRACT FROM AUTHOR]

It is difficult to implement high-resolution layer-to-layer alignment by direct inkjet printing because of the limitation of position accuracy of the common inkjet printer. The poor alignment of conventional printers generally causes large parasitic overlap capacitances between the gate and source/drain (S/D) of thin-film transistors (TFTs), which degrades device operating speeds. In this paper, a self-aligned method was proposed to minimize the parasitic overlap capacitance. In this method, a hydrophobic fluoropolymers (Cytop) coffee stripe prepared by inkjet printing was utilized to define the gate electrodes, and to dewet deposited ink droplet for self-aligned S/D electrodes. This kind of inkjet-printed self-aligned TFTs with In0.95Sc0.05Ox channel layer have a parasitic overlap capacitance as small as 0.31–0.45 pF. The TFTs in array exhibited an on/off ratio larger than $\textsf {10}^{\textsf {7}}$ and a maximum saturation mobility of $\textsf {4.63}\,\,\textsf {cm}^{\textsf {2}}\,\,\textsf {V}^{-\textsf {1}}\textsf {s}^{-\textsf {1}}$. [ABSTRACT FROM AUTHOR]

The fully inkjet-printed top-gate metal–oxide thin-film transistors (TFTs) with excellent electrical performance are realized with the gate dielectric layer of scandium zirconium oxide (Sc1Zr1Ox). It is found that adding of nitrate-based scandium oxide (ScOx) precursor into the chloride ligand-based zirconium oxide (ZrOx) precursor will reduce the corrosivity of the mixed solution, and the incorporation of Zr ions into ScOx will suppress the hydrogen-ion migration and eliminate the acceptor-like traps in pure ScOx. The fully printed indium gallium oxide (InGaO) TFTs based on Sc1Zr1Ox dielectric exhibited an average mobility of 10.8 cm $^{{2}} \text{V}^{\vphantom {R^{'}}-{1}} \cdot \text{s}^{-{1}}$ , a highest mobility of 12.9 cm $^{{2}} \cdot \text{V}^{-{1}} \cdot \text{s}^{-{1}}$ , negligible hysteresis, and excellent stability under both the negative and positive bias stresses. In addition, a resistor-loaded inverter was fabricated using a fully printed InGaO TFT, which exhibited the full swing characteristics and a maximum gain of 5 at 2 V. [ABSTRACT FROM AUTHOR]

The integration of antennas into disposable paper drones using inkjet printing technology is presented. These drones or unmanned aerial vehicles (UAVs) are developed using origami folding structures. Two vertical monopole antennas based on the same design concept are proposed and their performance assessed for two different conditions. The conditions relate to the placement of the other electronic components and circuits on the origami drones as reported in the literature. The first is when the electromechanical components and corresponding metallic layers are located in the wings. In this case, the effect of the possible location of the antenna as well as the deformation of the wings on S11 is discussed. The second is a more general case scenario which includes when the components and motors are placed at the tail and lower part of the body of the drone. The antenna elements are directly printed onto a photo paper substrate using silver nanoparticle conductive ink. Subsequently, the substrate is folded to create a paper drone. Low-cost desktop inkjet printing equipment is used to deposit the metallic tracks of the antenna. The designs target the current frequency bands employed in the control and wireless communication of commercial drones (2.4 GHz and 5 GHz bands). The purpose of this work is to investigate potential antenna scenarios for disposable drones which may one day be fully fabricated using inkjet printing technology. All antenna designs and studies have been simulated using CST Microwave Studio and compared well with experimental results. [ABSTRACT FROM AUTHOR]