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Neurotechnology includes artificial devices integrated with the neural tissue to mitigate the burden of neurological and mental disorders. This field has significantly expanded its range of applications thanks to the development of flexible, stretchable and injectable electronics. Now, the emergence of green electronics adds a new asset to the neurotechnology toolbox. Transient neurotechnology reduces the side effects of chronic implants and transforms inert devices into bio-active and bio-responsive structures. Ultimately, it holds the potential of bridging together technological devices with modern approaches in regenerative medicine. This review focuses on the rising potential of transient neurotechnology for human benefit, comprehensively summarises recent achievements and highlights feature needs and challenges.

International audience; Biosourced materials for organic electronics generate an increasing interest in the development of "eco-friendly" electronics. In fact, a considerable attention is focused on green polymers in order to reduce the impact of petroleum-sourced ones and to preserve the environmental sustainability, particularly in plant-derived materials. Such materials can provide huge potential such as the development of low-cost, large-area, and biocompatible electronic devices with good mechanical properties, for a large panel of applications, including biological and medical fields. In this paper, we report on the feasibility, the performance, and the electrical stability of flexible N-type organic field-effect transistors (OFETs) based on an agar biosubstrate and fullerene C-60 organic semiconductor. The fabricated OFETs exhibit a field-effect mobility mu(FE) = 7 x 10(-2) cm(2).V-1.s(-1), a threshold voltage V-TH = 14 V, a subthreshold slope SS = 4 V.dec(-1), and an on/off ratio I-Don/I-Doff = 7 x 10(3). The electrical characteristics of biosubstrate OFETs are presented and compared to those of OFETs fabricated on the glass substrate.

Using the earth-abundant natural biomaterials to manufacture functional electronic devices meets the sustainable requirement of green electronics, especially for the practical application of memristors in data storage and neuromorphic computing. However, the sneak currents flowing though the unselected cells in a large-scale cross-bar memristor array is one of the major problems which need to be tackled. The self-selecting memristors can solve the problem to develop compact and concise integrated circuits. Here, a sustainable natural biomaterial (anthocyanin, C

In this paper, a water based All Dielectric Frequency Selective Surface (ADFSS) is presented made of renewable materials. This surface is based on a modified dielectric resonator incorporating air ...

Natural biomaterials are potential candidates for the next generation of green electronics due to their biocompatibility and biodegradability. On the other hand, the application of biocomposite systems in information storage, photoelectrochemical sensing, and biomedicine has further promoted the progress of environmentally benign bioelectronics. Here, we mainly review recent progress in the development of biocomposites in data storage, focusing on the application of biocomposites in resistive random-access memory (RRAM) and field effect transistors (FET) with their device structure, working mechanism, flexibility, transient characteristics. Specifically, we discuss the application of biocomposite-based non-volatile memories for simulating biological synapse. Finally, the application prospect and development potential of biocomposites are presented., Graphical abstract

With the aim to address the physical limits of recent non-volatile flash memory, resistive switching memory has been intensively investigated as a strong competitor of the next generation memory technology. In particular, by combining the advantages of non-volatile resistive switching memory and degradable electronics, physically transient resistive switching memory has attracted more and more attention for its great potential applications in green electronics, degradable or implanted electronic devices, and secure information storage systems. This review attempts to present prompt and comprehensive summaries of recent progress in physically transient resistive switching memories that are comparable in performance to traditional resistive switching memory and expand the potential application fields of the memory devices. First, we introduce the concept and development of physically transient electronics and resistive switching memory. Second, an overview of various degradable resistive switching materials, including organic and inorganic active films, electrodes, and substrates, is described in detail. Third, recent advances in some representative mechanisms of physically transient resistive switching memories, including resistive switching and degradable mechanisms, are reviewed. Finally, we end the review with a summary and outlook, pointing out further challenges of physically transient resistive switching memory.

The growing demand of disposable electronics raises serious concerns for the corresponding increase in the amount of electronic waste, with severe environmental impact. Organic and flexible electronics have been proposed long ago as a more sustainable and energy-efficient technological platform with respect to established ones. Yet, such technology is leading to a drastic increase of plastic waste if common approaches for flexible substrates are followed. In this scenario, biodegradable solutions can significantly limit the environmental impact, actively contributing to eliminate the waste streams (plastic or electronic) associated with disposal of devices. However, achieving suitably scalable processes to pattern mechanically robust organic electronics onto largely available biodegradable substrates is still an open challenge. In this work, all-organic and highly flexible field-effect transistors, inkjet printed onto the biodegradable and compostable commercial substrate Mater-Bi, are demonstrated. Because of the thermal instability of Mater-Bi, no annealing steps are applied, producing devices with limited carrier mobility, yet showing correct n-type behavior and robustness to bending and crumpling. The degradation behavior of the final system shows unaltered biodegradability level according to ISO 14851. These results represent a promising step toward sustainable flexible and large-area electronics, combining energy and materials efficient processes with largely available biodegradable substrates.

The speed with which electronic products are updated is continuously increasing. Consequently, since waste electronic products can cause serious environmental pollution, the demand for electronic products made of biological materials is becoming increasingly urgent. Although biological memristors have significant advantages, their electrical characteristics still do not meet the requirements to be used in future nonvolatile memories. Therefore, how to control their electrical characteristics has become a popular topic of research. In this study, tunable biomemristors with an Al/tussah blood (TB)-carbon nanotube (CNT)/indium tin oxide (ITO)/glass structure were fabricated. Such a device exhibits stable bipolar resistance switching behavior and good retention characteristics (104 s). Experimental results show that the ON/OFF current ratio can be effectively controlled by modifying the CNT concentration in the TB-CNT composite film. Multilevel (8 levels, 3 bits per cell) storage capabilities can be achieved in the device by controlling its compliance current in order to achieve high-density storage. The resistance switching behavior originates from the formation and rupture of conductive oxygen vacancy filaments. TB is a promising natural biomaterial in the field of green electronics, and this research could blaze a new trail for the development of biological memory devices. Biomemristors with multilevel resistance states can be used as electronic synapses and are one of the choices for simulating biological synapses.

The rapid growth and adoption of microelectronics around the world has resulted in an increased awareness of potential environmental issues related to their use and disposal. Halogens, which have had various uses in microelectronics over the years, are known to emit toxic and corrosive gases during the disposal of electronic waste. Many organizations have applied pressure to the electronics industry to eliminate halogens completely (e.g., fluorine, chlorine and bromine) from their products. Among the various efforts towards environmentally-friendly products, making electronics completely halogen-free has gained significant attention, particularly in Asia and Europe. This initiative even impacts conformal coatings worldwide, on which most electronics rely for their long-term protection, reliability and high performance against water and other corrosive harsh environments. Among the various coating options, the Parylene family of conformal coatings offers beneficial properties to the microelectronics, improved over many properties offered by common epoxies, acrylics, urethanes and silicones. While Parylene N is the only commercially available Parylene that does not contain any halogens, its barrier performance against moisture and other corrosive chemicals is not quite as robust as the other Parylenes. To meet the industry's current and future requirements, a new halogen-free Parylene, ParyFree®, has been developed. This paper introduces a new Parylene type to the microelectronics industry and shares the characterization and qualification results of ParyFree® Parylene conformal coating for the protection, reliability and robust performance of microelectronics. Testing on the new coating includes IPX water resistance, corrosion resistance and qualification per IPC-CC-830B.

The field of “green electronics” is a cross-disciplinary research area which recognises naturally occurring or nature-inspired compounds and use them for the design and synthesis of eco-friendly synthetic-organic materials that are environmentally safe biodegradable/or biocompatible, for making of “Green-Devices.” The actual goal of this research field is to produce environmentally viable semiconducting materials and their applications in devices such as organic electronics to carry low energy intensity, low cost, negligible waste production, and also accomplish good functionalities. This chapter briefly reviews major research work based on ideologies of green chemistry in the synthetic strategies in making of semiconducting materials including small molecules and polymers or nature-inspired biocompatible materials and their applications in organic-green electronics.

Biocompatible materials have received increasing attention as one of the most important building blocks for flexible and transient memories. Herein, a fully biocompatible resistive switching (RS) memory electronic composed of a carbon dot (CD)-polyvinyl pyrrolidone (PVP) nanocomposite and a silver nanowire (Ag NW) network buried in a flexible gelatin film is introduced with promising nonvolatile RS characteristics for flexible and transient memory applications. The fabricated device exhibited a rewritable flash-type memory behavior, such as low operation voltage (≈-1.12 V), high ON/OFF ratio (>102), long retention time (over 104 s), and small bending radius (15 mm). As a proof of degradability, this transient memory can dissolve completely within 90 s after being immersed into deionized water at 55 °C; it can decompose naturally in soil within 6 days. This fully biocompatible memory electronic paves a novel way for flexible and wearable green electronics.

With the advancement of the modern ultrasmart world, our surroundings have become a dumping ground for electronic wastes, which not only is a threat to human lives, but has become dangerous for any living creature as well as for ecosystems. To keep our ecosystems healthy, the need has arisen to take immediate action against electronic waste. To overcome these issues, the design of smart devices with nontoxic, biodegradable or biocompatible materials is urgently desired, which will lead to devices that are easily recyclable, processable, and safe for the environment/living creatures. In recent times, piezoelectric/triboelectric nanogenerators (PNGs/TNGs) have attracted more and more attention among other renewable green energy-harvesting sources because of their easy accessibility, abundant sources, and conversion of mechanical energy into green electricity. Due to the toxic nature and incompatibility of inorganic/some organic-based PNGs/TNGs the designing of effective nature-driven bionanogenerator (PNG/TNG) devices with biocompatible/biodegradable materials would be a smart approach toward a future green electronics world. Here, we discuss the effectiveness of biowaste biodegradable materials in green energy harvesting technologies and their possible applications in a future smart/portable electronics world. Furthermore, using biowaste materials in energy-harvesting technology will help to clean biowastes from the environment as well as society.

Nowadays, sensor devices are developing fast. It is therefore critical, at a time when the availability and recyclability of materials are, along with acceptability from the consumers, among the most important criteria used by industrials before pushing a device to market, to review the most recent advances related to functional electronic materials, substrates or packaging materials with natural origins and/or presenting good recyclability. This review proposes, in the first section, passive materials used as substrates, supporting matrixes or packaging, whether organic or inorganic, then active materials such as conductors or semiconductors. The last section is dedicated to the review of pertinent sensors and devices integrated in sensors, along with their fabrication methods.

Flexible pressure sensors have received wide attention because of their potential applications in wearable electronics and electronic skins (e-skins). However, the high performance of the pressure sensors relies principally on the introduction of complex surface microstructures, which often involves either complicated procedures or costly microfabrication methods. Moreover, these devices predominantly use synthetic polymers as flexible substrates, which are generally nonbiodegradable or not ecofriendly. Here, we report a facile and scalable processing strategy to convert naturally rigid wood into reduced graphene oxide (rGO)-modified flexible wood (FW/rGO) via saw cutting, chemical treatment, and rGO coating, resulting in high-performance wood-based flexible piezoresistive pressure sensors. Benefiting from the largely deformable ribbon-like surface microstructures, the obtained wood-based pressure sensor displayed a high sensitivity of 1.85 kPa

Neuroprosthetics aims at restoring impaired or lost neurological and mental functions by exploiting technological advances in implantable and wearable devices. The performance of implantable devices, such as neural interfaces, relies upon the synergy between biology and machines. Should this synergy lack, numerous undesirable consequences might occur, such as rejection, infection, or malfunctioning. Several material properties like softness, electrochemical behaviour, biocompatibility, and biodegradability are among the features affecting the reliability of neural interfaces. In this review, the authors describe modern polymeric substrates and organic-based electrodes, offering the best combination of such characteristics. Their versatility in merging different properties derives from the accessible control over their molecular structure and blending. Compared to inorganic materials, organic materials have superior mechanical compliance with the soft tissue, and conjugated polymers also have an advantageous electrochemical transport mechanism at the interface with electrolytic solutions, involving both ionic and electronic conductivities. Hence, all-polymer neural interfaces would be convenient for a multitude of benefits, including low-cost manufacturing, increased biocompatibility, lightweight, transparency, and affinity with green electronics. This review also highlights materials strategies supporting the development of safe electronic interfaces based on organic materials and beneficial for various applications neuroprosthetics.

There is little question that the "electronic revolution" of the 20th century has impacted almost every aspect of human life. However, the emergence of solid-state electronics as a ubiquitous feature of an advanced modern society is posing new challenges such as the management of electronic waste (e-waste) that will remain through the 21st century. In addition to developing strategies to manage such e-waste, further challenges can be identified concerning the conservation and recycling of scarce elements, reducing the use of toxic materials and solvents in electronics processing, and lowering energy usage during fabrication methods. In response to these issues, the construction of electronic devices from renewable or biodegradable materials that decompose to harmless by-products is becoming a topic of great interest. Such "green" electronic devices need to be fabricated on industrial scale through low-energy and low-cost methods that involve low/non-toxic functional materials or solvents. This review highlights recent advances in the development of biodegradable materials and processing strategies for electronics with an emphasis on areas where green electronic devices show the greatest promise, including solar cells, organic field-effect transistors, light-emitting diodes, and other electronic devices.

Smart agriculture is a fast-growing research field. From one side, the increase of the human population is always demanding more food production. On the other side, the consciousness of the importance of diet quality requires a more controlled and higher quality production, both in terms of nutrition factors and lower use of pesticides. Thus, it is straightforward to apply the progress in electronics and sensors technology for reaching these different objectives. In this paper, we present an overview of the sensors applied for smart agriculture. Two different categories are presented: sensors for evaluating plant health and fruit conditions and sensors used to monitor the environmental condition where the plants are growing.

In this paper, a novel green composite for the realization of Fractional Order Elements is introduced and its experimental characterization is performed. The device has been realized by using Bacterial Cellulose and Ionic Liquids. The composite is used as the dielectric of a parallel plate capacitor. A model is proposed and compared to experimental data. The device shows new performance compared to previously introduced Bacterial-Cellulose-based devices and represents a viable technology for the realization of green Fractional Order Devices.

Triboelectric nanogenerators (TENGs) are versatile electronic devices used for environmental energy harvesting and self-powered electronics with a wide range of potential applications. The rapid development of TENGs has caused great concern regarding the environmental impacts of conventional electronic devices. Under this context, researching alternatives to synthetic and toxic materials in electronics are of major significance. In this review, we focused on TENGs based on natural polysaccharide materials. Firstly, a general overview of the working mechanisms and materials for high-performance TENGs were summarized and discussed. Then, the recent progress of polysaccharide-based TENGs along with their potential applications reported in the literature from 2015 to 2020 was reviewed. Here, we aimed to present polysaccharide polymers as a promising and viable alternative to the development of green TENGs and tackle the challenges of recycling e-wastes.

Renewable polymers have attracted extensive research interest as substitutes for fossil fuel-based materials because they are sustainable and biodegradable. With the rapid increase in the applications of electronic devices, the integration of renewable polymers with electronics not only enhances the economic benefit of waste natural resources but also conserves our environment. In this review, an overview of renewable materials used in electronics, including passive components (that is, substrates, photoresists, templates and dispersion agents) and active components (that is, luminescence layers, proton-transporting layers and charge-trapping layers), as well as their future perspective is provided. The relationships between chemical structures, their morphologies and the device characteristics will be discussed. It is hoped that this review will stimulate research and generate interest in applications of renewable materials for the electronics industry. Developing renewable polymeric materials for electronics applications is crucial toward next generation of green electronic industry. Current progress on the renewable materials used as the passive and active components in electronics is reviewed, where the correlation between the relationships of chemical structures, morphology and device characteristics is featured. Furthermore, their future perspectives are provided for foreseeable paths in the development of green electronics.

Paper-based (PB) green electronics is an emerging and potentially game-changing technology due to ease of recycling/disposal, the economics of manufacture and the applicability to flexible electronics. Herein, new-type printable PB strain sensors (PPBSSs) from graphite glue (graphite powder and methylcellulose) have been fabricated. The graphite glue is exposed to thermal annealing to produce surface micro/nano cracks, which are very sensitive to compressive or tensile strain. The devices exhibit a gauge factor of 804.9, response time of 19.6 ms and strain resolution of 0.038%, all performance indicators attaining and even surpassing most of the recently reported strain sensors. Due to the distinctive sensing properties, flexibility and robustness, the PPBSSs are suitable for monitoring of diverse conditions such as structural strain, vibrational motion, human muscular movements and visual control.

Green electronics is an emerging field of research which aims to manufacture devices in an environmentally friendly and sustainable way. Usually, the involved electronic materials are naturally occurring and non-toxic. Also, they can be processed using simple, low energy deposition processes and fabrication techniques. In this work, we present low voltage organic field-effect transistors (OFETs) using almond gum (AG) as the gate dielectric. AG is a natural, biodegradable insulator material that can be directly collected from almond trees and used without any further purification. Moreover, AG possesses interesting properties such as water solubility, ease of processing, good insulation, low leakage current, good film quality, and high capacitance making it a promising dielectric for OFET devices. Bottom gate/bottom contact p-channel OFETs have been processed on glass substrates with poly (3,6-di (2-thien-5-yl)-2,5-di (2-octyldodecyl)-pyrrolo [3,4-c] pyrrole-1,4-dione)thieno [3,2-b] thiophene) (DPPTTT) polymethyl methacrylate (PMMA) blend as the active layer and gold as the source and drain electrodes. The transistors operate at low voltage (VGS ≤ 3 V), with threshold voltages Vth as low as −0.8 V, saturated field effect mobilities μsat above 0.75 cm2 V−1 s−1, subthreshold swings SS around 270 mV/dec and ON/OFF current ratio equal to 103. The combined favourable properties of both almond gum and low voltage operated OFET devices have a high potential to pave a way towards using naturally occurring, biodegradable electronic materials in future disposable sensors or throwaway, low-end electronics.

In this article, an overview of recent advances in the field of battery-less near-field communication (NFC) sensors is provided, along with a brief comparison of other short-range radio-frequency identification (RFID) technologies. After reviewing power transfer using NFC, recommendations are made for the practical design of NFC-based tags and NFC readers. A list of commercial NFC integrated circuits with energy-harvesting capabilities is also provided. Finally, a survey of the state of the art in NFC-based sensors is presented, which demonstrates that a wide range of sensors (both chemical and physical) can be used with this technology. Particular interest arose in wearable sensors and cold-chain traceability applications. The availability of low-cost devices and the incorporation of NFC readers into most current mobile phones make NFC technology key to the development of green Internet of Things (IoT) applications.

Consumer roles in Corporate Social Responsibility (CSR) have not been in focus for electronics. A consumer perspective on knowledge about sustainability in electronics can help researchers better understand how knowledge about green electronics design affects consumer choices. This paper offers a framework for understanding consumer perspectives on green electronics as a basis for including consumer perspectives and education as part of green electronics design from a multidisciplinary perspective.

This paper proposes a review of several circuits for communication and wireless sensing applications implemented on cellulose-based materials. These circuits have been developed during the last years exploiting the adhesive copper laminate method. Such a technique relies on a copper adhesive tape that is shaped by a photo-lithographic process and then transferred to the hosting substrate (i.e., paper) by means of a sacrificial layer. The presented circuits span from UHF oscillators to a mixer working at 24 GHz and constitute an almost complete set of building blocks that can be applied to a huge variety communication apparatuses. Each circuit is validated experimentally showing performance comparable with the state-of-the-art. This paper demonstrates that circuits on cellulose are capable of operating at record frequencies and that ultra- low cost, green i.e., recyclable and biodegradable) materials can be a viable solution to realize high frequency hardware for the upcoming Internet of Things (IoT) era.

The employ of natural biomaterials as the basic building blocks of electronic devices is of growing interest for biocompatible and green electronics. Here, resistive switching (RS) devices based on naturally silk protein with configurable functionality are demonstrated. The RS type of the devices can be effectively and exactly controlled by controlling the compliance current in the set process. Memory RS can be triggered by a higher compliance current, while threshold RS can be triggered by a lower compliance current. Furthermore, two types of memory devices, working in random access and WORM modes, can be achieved with the RS effect. The results suggest that silk protein possesses the potential for sustainable electronics and data storage. In addition, this finding would provide important guidelines for the performance optimization of biomaterials based memory devices and the study of the underlying mechanism behind the RS effect arising from biomaterials.

In this letter, a miniaturized, flexible and high data dense dual-polarized chipless radio frequency identification (RFID) tag is presented. The tag is designed within a minuscule footprint of 29 × 29 mm2 and has the ability to encode 38-bit data. The tag is analyzed for flexible substrates including Kapton® HN DuPont™ and HP photopaper. The humidity sensing phenomenon is demonstrated by mapping the tag design, using silver nano-particle based conductive ink on HP photopaper substrate. It is observed that with the increasing moisture, the humidity sensing behavior is exhibited in RF range of 4.1–17.76 GHz. The low-cost, bendable and directly printable humidity sensor tag can be deployed in a number of intelligent tracking applications.

In this paper the experimental results of a compact low-power rectenna in paper substrate, designed to operate in the Wi-Fi band, are presented. The complete prototype, based on an annular slot antenna and a single-diode rectifier, features a weight of 1.5 grams and shows an RF-to-dc conversion efficiency in the design band of about 40 % for a -10 dBm available input power, of about 28 % at -15 dBm, and in the range [10, 22] % at -20 dBm, corresponding to an output DC voltage in the order of 320, 240 and 60 mV respectively. Additionally, the rectenna features an efficiency higher then 7 % in the whole band 1.8-2.7 dBm for a power density estimated around 3 μW/cm2.

Energy harvesting is well established as one of the prominent enabling technologies [along with radio-frequency identification (RFID), wireless power transfer, and green electronics] for the pervasive development of Internet of Things (IoT). This paper focuses on a particular, yet broad, class of systems that falls in the IoT category of large area electronics (LAE). This class is represented by “smart surfaces.” The paper, after an introductory overview about how smart surfaces are collocated in the IoT and LAE scenario, first deals with technologies and architectures involved, namely, materials, antennas, RFID systems, and chipless structures; then, some exemplifying solutions are illustrated to show the present development of these concurrent technologies in this area and to stimulate further solutions. Conclusions and future trends are then drawn.

Although paper electronics is a compelling concept, the large surface roughness and opaqueness of most paper substrates has hindered its development from a dormant idea to a thriving technology. A recent demonstration of transparent paper with nanoscale surface roughness has revived an interest in using renewable cellulose substrates for electronics and optoelectronics. In this short review, we will first summarize the recent progress of transparent paper electronics through structure engineering. We will also discuss the properties and functionalization of transparent paper, such as surface roughness, printability, thermal stability, etc. Finally, we will summarize the recent achievements on proof-of-concepts of transparent paper, which pave the way for next-generation green electronics fabricated with roll-to-roll printing methods. Advantages of transparent paper over traditional flexible plastic substrates and its challenges will also be discussed.

Fast, simple, cost-efficient, eco-friendly, and design-flexible patterning of high-quality graphene from abundant natural resources is of immense interest for the mass production of next-generation graphene-based green electronics. Most electronic components have been manufactured by repetitive photolithography processes involving a large number of masks, photoresists, and toxic etchants; resulting in slow, complex, expensive, less-flexible, and often corrosive electronics manufacturing processes to date. Here, a one-step formation and patterning of highly conductive graphene on natural woods and leaves by programmable irradiation of ultrafast high-photon-energy laser pulses in ambient air is presented. Direct photoconversion of woods and leaves into graphene is realized at a low temperature by intense ultrafast light pulses with controlled fluences. Green graphene electronic components of electrical interconnects, flexible temperature sensors, and energy-storing pseudocapacitors are fabricated from woods and leaves. This direct graphene synthesis is a breakthrough toward biocompatible, biodegradable, and eco-friendlily manufactured green electronics for the sustainable earth. National Research Foundation (NRF) T.-S.D.L. and S.P. contributed equally to this work. This work was supported by the NRF-Investigatorship, Award No. NRF-NRFI2016-05. This work was also supported by an NRF Fellowship (NRF-NRFF2015-02) from the Singapore National Research Foundation.

Paper is a flexible material, commonly used for information storage, writing, packaging, or specialized purposes. It also has strong appeal as a substrate in the field of flexible printed electronics. Many applications, including safety, merchandising, smart labels/packing, and chemical/biomedical sensors, require an energy source to power operation. Here, progress regarding development of photovoltaic and energy storage devices on cellulosic substrates, where one or more of the main material layers are deposited via solution processing or printing, is reviewed. Paper can be used simply as the flexible substrate or, exploiting its porous fiber‐like nature, as an active film by infiltration or co-preparation with electronic materials. Solar cells with efficiencies of up to 9% on opaque substrates and 13% on transparent substrates are demonstrated. Recent developments in paper‐based supercapacitors and batteries are also reviewed with maximum achieved capacity of 1350 mF cm−2and 2000 mAh g−1, respectively. Analyzing the literature, it becomes apparent that more work needs to be carried out in continuing to improve peak performance, but especially stability and the application of printing techniques, even roll‐to‐roll processing, over large areas. Paper is not only environmentally friendly and recyclable, but also thin, flexible, lightweight, biocompatible, and inexpensive.

This letter presents the design of a Schottky diode frequency doubler suitable for harmonic RFID tags. A microwave frequency doubler is implemented in a cellulose-based (paper) substrate, i.e., an ultra-low cost, recyclable and biodegradable material. The circuit exploits a distributed microstrip structure that is fabricated using a copper adhesive laminate to have low conductor losses. The measurements show a conversion loss of 13.4 dB at the output frequency of 2.08 GHz. This is achieved with an available input power of -10 dBm only. Finally a harmonic RFID experiment proves a reading range of 50 cm, obtained by transmitting 0 dBm and receiving a second harmonic of -60 dBm, i.e., well above the sensitivity of a typical microwave receiver.

In this paper a novel approach is proposed to solve the issue of the absolute accuracy required by the most of the passive chip-less RFID sensors. To this purpose the sensor information is encoded as the phase difierence between two signals, one of the two acting as the reference signal for the other one. First the tag receives a carrier at frequency f0, then two equal signals at frequency 2f0 are generated by means of a diode-based frequency doubler and a power divider. At this point one of the two signals is phase-shifted using a passive sensing element. Finally the 2f0 signals are re-irradiated by exploiting two orthogonally polarized antennas. With this approach the sensor information can be extracted by a suitable reader equipped with two complex (I/Q) receivers. The idea will be flrst developed from a theoretical basis and then verifled with several particular cases. The novel tag concept is compatible with paper substrate and inkjet printing technology since antennas diodes and passive sensing elements, i.e., all the main tag components, are going to be developed on paper materials.

This paper presents the design of a novel rectenna based on a tapered annular slot and a single-diode rectifier, optimized to operate in the Wi-Fi band and in presence of low input power (Pavs=-15 dBm). In order to obtain a compact layout a double-layer architecture has been considered, according to which the interior metal surface of the annular slot is employed as ground plane for the rectifying circuit placed on the other side of the substrate. As a result, a rectenna with an active area of only 40 × 33 mm2 and an efficiency included between 26.5 and 28% has been obtained. The antenna has been fabricated in paper substrate and tested in the anechoic chamber. Then, the rectifier has been designed and optimized within the Advanced Design System suite. Finally, the rectenna performance has been discussed and compared to the State of the Art (SoA).

In this paper, novel Bowtie antennas which cover complete UHF RFID band (860-960MHz), fabricated on various ultra-low-cost substrates using state-of-the-art printing technologies are investigated a ...

In this paper, we demonstrate an RFID tag antenna manufactured by advanced inkjet printing technology on paper substrate using novel hole-matching technique for reducing the consumption of substrat ...

The search for green energy sources has populated the research arena with significant emphasis on green electronics, green fuels, and green batteries that reduce waste, emissions, and environmental toxicity. Simultaneously, nanotechnology has developed substantially in the recent years and the emerging area of nanoenergetics has shown impressive discoveries that can aid in the search for alternative and green energies. The use of exotic materials in these fields and even enzymes has led scientists to be able to cross-link biomolecules and nanotechnology circuits, which can be important points in the search of novel energy searches. This paper discusses a biochemical energy-generating unit driven by ion fluctuations and spontaneous enzyme conformational changes. The paper lays also the theoretical thermodynamical foundation of the nanoenergy unit and to exploit the principle of nonadditivity and equilibrium as main forces in driving an energy-generating reaction.

Presently, large quantities of waste mobile phones are being generated in Nigeria with a significant proportion in storage. This paper investigated the behavior of consumers in Nigeria towards this waste stream and their willingness to participate in waste mobile phones recycling. This study also assessed the willingness of consumer's to pay for a more ‘environment friendlier’ phone – the so-called ‘green phone’. We performed a principal component analysis with varimax rotation in order to condense some of our questions into a smaller set of factors. We developed a model to estimate and explain the willingness to pay (WTP) a premium for ‘green’ cell phones. The model showed that the significant predictors of willingness to pay extra for green electronics include awareness and concern about the deteriorating environment, age, and the general attitude towards the environment. About 65% of the respondents are either ‘willing’ or ‘very willing’ to drop-off no-longer-in-use electronics at a nearby recycling facility. Majority of the respondents are also very willing to pay a premium for a green phone. Considering the increasing waste generation by this sector, it has become expedient that a recycling program be introduced for these potentially harmful waste materials.

Management of used electrical and electronic equipment (EEE) is becoming a major issue as each year around 20 to 50 million tonnes of electronic waste (e-waste) is generated worldwide. EEE contains over 1000 materials of which lead (Pb) has been one of the targets of the regulators forcing manufacturers to adopt lead free products. Industry has come up with several lead free solders with preference given to alloys containing tin, silver, and copper but there is no ,drop-in' substitute to leaded solder. Issues with lead free solders such as temperature, intermetallics, tin whisker, tin pest, and reliability are yet to be resolved. The paper investigated the contribution of lead free soldering to green electronics in a holistic way. Global lead free movement has reached a point of no return. However, it is necessary to make sure that life span of EEE is not shortened thereby resulting in an unforeseen increase in e-waste or problem shifting does not occur by shifting a problem from one life cycle to another or from one category/media to another.

Today's consumer electronics, such as cell phones, tablets and other portable electronic devices, are typically made of non-renewable, non-biodegradable, and sometimes potentially toxic (for example, gallium arsenide) materials. These consumer electronics are frequently upgraded or discarded, leading to serious environmental contamination. Thus, electronic systems consisting of renewable and biodegradable materials and minimal amount of potentially toxic materials are desirable. Here we report high-performance flexible microwave and digital electronics that consume the smallest amount of potentially toxic materials on biobased, biodegradable and flexible cellulose nanofibril papers. Furthermore, we demonstrate gallium arsenide microwave devices, the consumer wireless workhorse, in a transferrable thin-film form. Successful fabrication of key electrical components on the flexible cellulose nanofibril paper with comparable performance to their rigid counterparts and clear demonstration of fungal biodegradation of the cellulose-nanofibril-based electronics suggest that it is feasible to fabricate high-performance flexible electronics using ecofriendly materials., The rapid evolution of consumer electronics means that out-of-date devices quickly end up in the scrap heap. Here, the authors fabricate electrical components using biodegradable and flexible cellulose nanofibril paper—a natural sustainable resource derived from wood.

This paper presents the design and implementation in paper substrate of a harmonic RFID chipless sensing tag. The proposed sensor is based on a Wheatstone bridge, where two of the four impedances change dynamically according to a physical parameter that has to be monitored. The passive tag is interrogated by a signal at f 0 = 1.04 GHz and the signal transmitted back to the reader at 2f 0 = 2.08 GHz is proportional to the magnitude of the parameter variation. A harmonic RFID experiment proves that this kind of architecture is capable of providing a dynamic range of more than 40 dB.

This paper presents, for the first time, a 24-GHz Continuous Wave (CW) radar front-end, entirely realized on a cellulose-based (i.e. paper) substrate. The front-end uses a microstrip circuitry that is fabricated using a copper adhesive laminate to have low conductor losses. A single dielectric layer is adopted to reduce complexity and, in perspective, costs. The radar exploits an external oscillator and transmits a power of about 2 mW. The antenna has a gain of 7 dBi and features an half-power beam width of 42 degrees. Its efficiency is 25%, including the feeding line. A singly-balanced diode mixer is adopted in the receiver chain. The mixer conversion loss is 11 dB with a local oscillator driving level of 0 dBm. In Doppler mode, the radar is able to detect a small fan (i.e. the movement of its rotor) at 1 m distance from the antenna. This contribution demonstrates that circuits on cellulose are capable to operate up to the boundary between microwave and millimeter-waves.

This paper summarizes the most important technologies, concurrently participating to build the technological platform needed for a realistic implementation of the Internet of Things (IoT) paradigm. At the present state of the evolution of IoT, these technologies are mostly: Radio Frequency IDentification (RFID), Green Electronics (GE), Wireless Power Transfer (WPT) and Energy Harvesting (EH). This contribution briefly explains the reason for that, and shows a collection of scientific contributions which can be seen as examples. The deep description of the proposed systems can be found in the relative referenced papers.

In this paper we report results concerning the use of paper as substrate and as an electronic component for the next generation of sustainable low cost electronic systems, where different examples of applications are given.

This paper presents a miniaturized Doppler radar that can be used as a motion sensor for low-cost Internet of things (IoT) applications. For the first time, a radar front-end and its antenna are integrated on a multilayer cellulose-based substrate, built-up by alternating paper, glue and metal layers. The circuit exploits a distributed microstrip structure that is realized using a copper adhesive laminate, so as to obtain a low-loss conductor. The radar operates at 24 GHz and transmits 5 mW of power. The antenna has a gain of 7.4 dBi and features a half power beam-width of 48 degrees. The sensor, that is just the size of a stamp, is able to detect the movement of a walking person up to 10 m in distance, while a minimum speed of 50 mm/s up to 3 m is clearly measured. Beyond this specific result, the present paper demonstrates that the attractive features of cellulose, including ultra-low cost and eco-friendliness (i.e., recyclability and biodegradability), can even be exploited for the realization of future high-frequency hardware. This opens opens the door to the implementation on cellulose of devices and systems which make up the “sensing layer” at the base of the IoT ecosystem.