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This study reports on the first all-printed vertically stacked organic electrochemical transistors (OECTs) operating in accumulation mode; the devices, relying on poly([4,4?-bis(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)-2,2?-bithiophen-5,5?-diyl]-alt-[thieno[3,2-b]thiophene-2,5-diyl]) (pgBTTT) as the active channel material, are fabricated via a combination of screen and inkjet printing technologies. The resulting OECTs (W/L ≈5) demonstrate good switching performance; gm, norm ≈13 mS cm?1, µC* ≈21 F cm?1 V?1 s?1, ON?OFF ratio > 104 and good cycling stability upon continuous operation for 2 h. The inkjet printing process of pgBTTT is established by first solubilizing the polymer in dihydrolevoglucosenone (Cyrene), a non-toxic, cellulose-derived, and biodegradable solvent. The resulting ink formulations exhibit good jettability, thereby providing reproducible and stable p-type accumulation mode all-printed OECTs with high performance. Besides the environmental and safety benefits of this solvent, this study also demonstrates the assessment of how the solvent affects the performance of spin-coated OECTs, which justifies the choice of Cyrene as an alternative to commonly used harmful solvents such as chloroform, also from a device perspective. Hence, this approach shows a new possibility of obtaining more sustainable printed electronic devices, which will eventually result in all-printed OECT-based logic circuits operating in complementary mode., This project received funding from the European Union's Horizon 2020 research and innovation program under grant agreement no. 964677 (MITICS). The authors would like to thank Jessica Åhlin for valuable electrolyte discussions. A.M. and P.A.E. thank Vinnova for financial support (grant agreement no. 2023-01337). W.M., L.B., and A.G. thank the FWO Vlaanderen for financial support (WEAVE project G025922N and Ph.D. grant 1S70122N)

The development of electronics with net zero carbon emissions through more efficient and environmentally friendly materials and processes is still a challenge. Here, alternative chemical synthesis routes of metal conductive nanoparticles, based on biodegradable materials are explored, such as nickel, iron–nickel alloy and iron nanoparticles, to be used, in the long term, as fillers in inks for inject printing. Thus, Ni and FeNi metal nanoparticles of 25–12 nm, forming aggregates of 614–574 nm, respectively, are synthesized in water in the presence of a polyol and a reducing agent and under microwave heating that enables a more uniform and fast heating. Iron nanoparticles of 120 ± 40 nm are synthesized in polyol that limits the aggregation and the oxidation degree. Commercial metal nanoparticles of iron and nickel, are coated with ethylene glycol and used for comparison. The conductivity of nanoparticles when pressed into pellets remains similar for both commercial and synthesized samples. However, when deposited on a strip line and heated, synthesized Ni, FeNi, and Fe nanoparticles show significant conductivity and interesting magnetic properties. It is demonstrated that the nanosize facilitates sintering at reduced temperatures and the capping agents prevent oxidation, resulting in promising conductive fillers for printed electronic applications., B.C.P. and C.D.U. contributed equally to this work. This research wasfunded by the Spanish Ministry of Science, grant number PID2020-13480RB-I00 and TED2021-130191B-C43, and by the EU-commission,HORIZON-CL4-2021-DIGITAL-EMERGING-01 (HyPELignum), PROJECTNo.101070302 (2022-26). M.S. was supported by a Margarita Salas fel-lowship financed by the European Union-NextGenerationEU and thePlan for Recovery, Transformation and Resilience. Authors also acknowl-edge the Servicio Interdepartamental de Investigación at the Universi-dad Autónoma de Madrid, the TEM Service at the Centro de BiologíaMolecular Severo Ochoa (CBMSO, CSIC-UAM), SEM at MiNa Labora-tory (IMN, funding from CM (project S2018/NMT-4291 TEC2SPACE),MINECO (project CSIC13-4E-1794) and EU (FEDER, FSE)) and XRD, FTIR,the elemental and thermal analysis, and the characterization and growthof thin films service at ICMM/CSIC.

This work demonstrates sensitive and low-cost piezoelectric sensors on skin-friendly, ultrathin, and conformable substrates combined with organic electrochemical transistors (OECTs) for the detection and amplification of alternating low-voltage input signals. The fully screen-printed (SP) piezoelectric sensors were manufactured on commercially available tattoo paper substrates, while the all-printed OECTs, relying on an extended gate electrode architecture, were manufactured either by solely using SP or by combining SP and aerosol jet printing (AJP) on PET substrates. Applying a low-voltage signal (±25 mV) to the gate electrode of the SP+AJP OECT results in approximately five times higher current modulation as compared to the fully SP reference OECT. The tattoo paper-based substrate enables transfer of the SP piezoelectric sensor to the skin, which in turn allows for radial pulse monitoring when combined with the SP+AJP OECT; this is possible due to the ability of the conformable sensor to convert mechanical vibrations into voltage signals along with the highly sensitive current modulation ability of the transistor device to further amplify the output signal. The results reported herein pave the way toward all-printed fully conformable wearable devices with high sensitivity to be further utilized for the real-time monitoring of electrophysiological signals.

The transition to a sustainable society is driving the development of green electronic solutions designed to have a minimal environmental impact. One promising route to achieve this goal is to construct electronics from biobased materials like cellulose, which is carbon neutral, non‐toxic, and recyclable. This is especially true for internet‐of‐things devices, which are rapidly growing in number and are becoming embedded in every aspect of our lives. Here, paper‐based sensor circuits are demonstrated, which use triboelectric pressure sensors to help elderly people communicate with the digital world using an interface in the form of an electronic “book”, which is more intuitive to them. The sensors are manufactured by screen printing onto flexible paper substrates, using in‐house developed cellulose‐based inks with non‐hazardous solvents. The triboelectric sensor signal, generated by the contact between a finger and chemically modified cellulose, can reach several volts, which can be registered by a portable microcontroller card and transmitted by Bluetooth to any device with an internet connection. Apart from the microcontroller (which can be easily removed), the whole system can be recycled at the end of life. A triboelectric touch interface, manufactured using printed electronics on flexible paper substrates, using cellulose‐based functional inks is demonstrated. These metal‐free green electronics circuits are implemented in an “electronic book” demonstrator, equipped with wireless communication that can control remote devices, as a step toward sustainable and recyclable internet‐of‐things devices., The authors would like to acknowledge funding from Vinnova through theD igital Cellulose Competence Center (DCC), Diary number 2016–05193, the Swedish Foundation for Strategic Research (Smart Intra-body network; grant RIT15-0119), and the Norrköping municipality fund for research and development (Accessibility and remembering – storytelling and innovative media use in elderly care homes, 2020. Grant: KS 2020/0345). The work was also supported by Treesearch.se. The authors thank Patrik Isacsson and co-workers at Ahlstrom Munksjö for providing the paper substrates and for valuable know-how as part of the collaboration within DCC, as well as Erik Gabrielsson, Daniel Simon, Elisabet Cedersund, and Lars Herlogsson for their involvement in the work on the original Mediabook platform.

High-throughput production methods such as screen printing can bring stretchable electronics out of the lab into the market. Most stretchable conductor inks for screen printing are based on silver nanoparticles or flakes due to their favorable performance-to-cost ratio, but silver is prone to tarnishing and corrosion, thereby limiting the stability of such conductors. Here, we report on a cost-efficient and scalable approach to resolve this issue by developing screen printable inks based on silver flakes chemically coated by a thin layer of gold. The printed stretchable AgAu conductors reach a conductivity of 8500 S cm-1, remain conductive up to 250% strain, show excellent corrosion and tarnishing stability, and are used to demonstrate wearable LED and NFC circuits. The reported approach is attractive for smart clothing, as the long-term functionality of such devices is expected in a variety of environments., Funding Agencies|Swedish Foundation for Strategic Research; Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials at Linkoeping University [2009-00971]

Wood is an inherently hygroscopic material which tends to absorb moisture from its surrounding. Moisture in wood is a determining factor for the quality of wood being employed in construction, since it causes weakening, deformation, rotting, and ultimately leading to failure of the structures resulting in costs to the economy, the environment, and to the safety of residents. Therefore, monitoring moisture in wood during the construction phase and after construction is vital for the future of smart and sustainable buildings. Employing bio-based materials for the construction of electronics is one way to mitigate the environmental impact of such electronics. Herein, a bio-graphene sensor for monitoring the moisture inside and around wooden surfaces is fabricated using laser-induced graphitization of a lignin-based ink precursor. The bio-graphene sensors are used to measure humidity in the range of 10% up to 90% at 25 degrees C. Using laser induced graphitization, conductor resistivity of 18.6 ohm sq(-1) is obtained for spruce wood and 57.1 ohm sq(-1) for pine wood. The sensitivity of sensors fabricated on spruce and pine wood is 2.6 and 0.74 M omega per % RH. Surface morphology and degree of graphitization are investigated using scanning electron microscopy, Raman spectroscopy, and thermogravimetric analysis methods., Funding Agencies|Vinnova for the Digital Cellulose Competence Center (DCC) [2016-05193]; Stora Enso AB

Microfluidic surface chemistry can enable control of capillary-driven flow without the need for bulky external instrumentation. A novel pondered nonhomogeneous coating defines regions with different wetting properties on the microchannel walls. It changes the curvature of the liquid–air meniscus at various channel cross-sections and consequently leads to different capillary pressures, which is favorable in the strive toward automatic flow control. This is accomplished by the deposition of hydrophilic coatings on the surface of multilevel 3D-printed (3DP) microfluidic devices via inkjet printing, thereby retaining the surface hydrophilicity for at least 6 months of storage. To the best of our knowledge, this is the first demonstration of capillary flow control in 3DP microfluidics enabled by inkjet printing. The method is used to create “stop” and “delay” valves to enable preprogrammed capillary flow for sequential release of fluids. To demonstrate further utilization in point-of-care sensing applications, screen printed organic electrochemical transistors are integrated within the microfluidic chips to sense, sequentially and independently from external actions, chloride anions in the (1–100) × 10-3 m range. The results present a cost-effective fabrication method of compact, yet comprehensive, all-printed sensing platforms that allow fast ion detection (<60 s), including the capability of automatic delivery of multiple test solutions., Peer Reviewed, Postprint (published version)

Microfluidic surface chemistry can enable control of capillary-driven flow without the need for bulky external instrumentation. A novel pondered nonhomogeneous coating defines regions with different wetting properties on the microchannel walls. It changes the curvature of the liquid–air meniscus at various channel cross-sections and consequently leads to different capillary pressures, which is favorable in the strive toward automatic flow control. This is accomplished by the deposition of hydrophilic coatings on the surface of multilevel 3D-printed (3DP) microfluidic devices via inkjet printing, thereby retaining the surface hydrophilicity for at least 6 months of storage. To the best of our knowledge, this is the first demonstration of capillary flow control in 3DP microfluidics enabled by inkjet printing. The method is used to create “stop” and “delay” valves to enable preprogrammed capillary flow for sequential release of fluids. To demonstrate further utilization in point-of-care sensing applications, screen printed organic electrochemical transistors are integrated within the microfluidic chips to sense, sequentially and independently from external actions, chloride anions in the (1–100) × 10−3 m range. The results present a cost-effective fabrication method of compact, yet comprehensive, all-printed sensing platforms that allow fast ion detection (<60 s), including the capability of automatic delivery of multiple test solutions. © 2023 The Authors., Correspondence Address: P. Andersson Ersman; RISE Research Institutes of Sweden, Digital Systems, Smart Hardware, Printed, Bio- and Organic Electronics, Norrköping, 60233, Sweden. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska‐Curie grant agreement no. 813863 (BORGES).

Stretchable organic electrochemical transistors (OECTs) are promising for wearable applications within biosensing, bio-signal recording, and addressing circuitry. Efficient large-scale fabrication of OECTs can be performed with printing methods but to date there are no reports on high-performance fully printed stretchable OECTs. Herein, this challenge is addressed by developing fully screen-printed stretchable OECTs based on an architecture that minimizes electrochemical side reactions and improves long-term stability. Fabrication of the OECTs is enabled by in-house development of three stretchable functional screen-printing inks and related printing processes. The stretchable OECTs show good characteristics in terms of transfer curves, output characteristics, and transient response up to 100% static strain and 500 strain cycles at 25% and 50% strain. The strain insensitivity of the OECTs can be further improved by strain conditioning, resulting in stable performance up to 50% strain. Finally, an electrochromic smart pixel is demonstrated by connecting a stretchable OECT to a stretchable electrochromic display. It is believed that the development of screen-printed stretchable electrochemical devices, and OECTs in particular, will pave the way for their use in wearable applications and commercial products., Funding Agencies|Swedish Foundation for Strategic Research; Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials at Linkoping University [2009-00971]

This work demonstrates a novel fabrication approach based on the combination of screen and aerosol jet printing to manufacture fully printed organic electrochemical transistors (OECTs) and OECT-based logic circuits on PET substrates with superior performances. The use of aerosol jet printing allows for a reduction of the channel width to ≈15 µm and the estimated volume by a factor of ≈40, compared to the fully screen printed OECTs. Hence, the OECT devices and OECT-based logic circuits fabricated with the proposed approach emerge with a high ON/OFF ratio (103?104) and remarkably fast switching response, reaching an ON/OFF ratio of >103 in 4?8 ms, which is further demonstrated by a propagation delay time of just above 1 ms in OECT-based logic inverter circuits operated at a frequency of 100 Hz. All-printed monolithically integrated OECT-based five-stage ring oscillator circuits further validated the concept with a resulting self-oscillation frequency of 60 Hz., Funding: This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 813863 (BORGES) and the European Union's Horizon 2020 research and innovation programme under the grant agreement No 825339 (WEARPLEX).

Low weight, small footprint, and high performances are essential requisites for the implementation of energy storage devices within consumer electronics. One way to achieve these goals is to increase the thickness of the active material layer. In this work, carbonized and graphitized rayon felt, a cellulose-derived material, is used as a three-dimensional current collector scaffold to enable the incorporation of large amount of active energy storage materials and ionic liquid-based gel electrolyte in the supercapacitor devices. PEDOT:PSS, alone or in combination with active carbon, has been used as the active material. Three-dimensional supercapacitors with high per unit area capacitance (more than 1.1 F/cm(2)) have been achieved owing to the loading of large amount of active material in the felt matrix. Areal energy density of more than 101 mu Wh/cm(2) and areal power density of more than 5.9 mW/cm(2) have been achieved for 0.8 V operating voltage at a current density of 1 mA/cm(2). A nanographite material was found to be beneficial in reducing the internal serial resistance of the supercapacitor to lower than 1.7 omega. Furthermore, it was shown that even after 2000 times cycling test, the devices could still retain its performance with at least 88% coulombic efficiency for all the devices. All the materials are readily available commercially, environmentally sustainable and the process can potentially be upscaled with industrial process., Funding Agencies|Knut och Alice Wallenbergs Stiftelse; Onnesjo foundation; Stiftelsenfor Strategisk Forskning; VINNOVA

The society is transitioning towards a circular economy and the Digital Cellulose Center (DCC) that develops green electronics may play an important role in it. The research within the DCC focuses on the topic of digital cellulose, where cellulose is combined with electroactive material, making it possible to develop electrically active cellulose products that can communicate with the digital world while remaining sustainable. This could mean entirely new types of active packaging solutions, able to sense and adapt to their surroundings, or paper rolls able to store energy from solar cells or wind power [1]. This document offers guidance for the DCC stakeholders on the choice of sustainable materials for green electronics, focusing on the two life cycle phases of a product: • Raw materials • End-of-life Since the DCC green electronics are still in the development stage, a future scenario analysis has been applied in order to envision the possible future outcomes. The DCC green electronics have been explored in two opposite future scenarios: • Stuck in the Mud – A business-as-usual scenario, where the year 2045 is more or less the same as year 2022. • Circular Dawn – Where the circular economy has become a new normal and the whole society is thriving in a resource-efficient, circular and biobased economy. The guideline contains a sustainability checklist adapted to the needs of the DCC stakeholders for more informed decision-making and for being able to drive the development towards a circular economy, i. e. the future scenario Circular Dawn.