Cellulose electronics and photonics: a new challenge for materials a new opportunity for devices III

Resume : We have been observing a rapid and growing interest concerning the utilization of materials of renewable origin for a wide range of applications. One of the most representative example is cellulose, not only in the form of raw material mainly for pulp and paper production, but also in the development of advanced materials/products with tailor-made properties, especially the ones based on nanostructures. Five years ago paper electronics was pure science fiction, but today we have already several paper-based electronics like integrated circuits, supercapacitors, batteries, fuel cells, solar cells, transistors, microwave electronics, digital logic/computation, displays, user interfaces, transparent substrates, substrates with high strength, wearable devices, and new rapid diagnostic tests. These devices with their associated physics and processing will play an important and relevant role to our society special for environmental sustainability, safety, communication, health, and performance. In this talk we will discuss the state of the art and potential future directions in paper-based electronics with special emphasis to the work developed at CENIMAT|i3N, covering electronic devices, smart displays, printed electronics, sensors and rapid diagnostic tests.

Resume : Bacterial NanoCellulose (BNC) is a nanofibrillar exopolysaccharide produced by certain acetic acid bacteria, synthesized as a 3D randomly oriented and highly hydrated nanofibrillar network. Commercial exploitation of BNC has its roots in the Philippines, from as early as 1819. After several fermentation trials under static culture, Nata de Coco cottage industry has grown to become a successful traditional fermented food business in several countries of the Pacific region. In the 1990s, several Japanese companies have collaborated to set up interdisciplinary research programs on the commercial production of microbial cellulose. However, due to the lack of efficient fermentation systems, commercial production of BNC was never achieved. Another example of the tentative large-scale production and commercialization of BNC, is the joint effort of two American companies by using a deep tank fermentation technique. With this technology, a commercial product, called CellulonTM, was aimed at different applications, including human food. By mid-nineties, NutraSweet Kelco Company purchased the microbial cellulose business and launched the BNC product as PrimaCelTM, also aimed at food applications. These products, however, never reach full commercial scale, presumably due to the high capital and production costs involved. Much effort has been devoted to designing an economical process for BNC production, by optimizing both upstream and downstream processes, including the evaluation of several culture media compositions, fermentation systems, genetic engineering and post-production modification processes. However, still the scientific literature propagates de idea that the technological production of BNC is extremely expensive. The current status of BNC production and technologies will be reviewed, with an emphasis on electrochemical energy storage and conversion systems. Specifically, recent advances in the utilization of BC in capacitors, secondary batteries and electrocatalysis will be discussed.

Resume : The small security prints found on banknotes or credit cards are often referred to as “holograms” due to their particular optical properties, giving rise to specific iridescence and angular response. When the angular response varies smoothly within a specific 2D pattern, it gives rise to an illusion of depth, a feature reminiscent of those made by dedicated holographic methods. Producing such an effect by relying only on a self-assembly approach represents a challenge for both fundamental and applied points of view. In this talk, I will present how the self-assembly of cellulose nanocrystals (CNCs), a fully bio-sourced and renewable resource, can be guided into forming patterned photonic films with illusion of depth. CNCs are anisotropic and chiral colloidal nanorods able to self-assemble spontaneously into a cholesteric phase above a critical concentration. Upon solvent evaporation, these suspensions are able to self-assemble into photonic structures,[1] and the application of a moderate magnetic field (µ0H ≈ 0.5 T) enables an angular control of the local helical direction of the domains, due to their negative diamagnetic anisotropy.[2-4] The method is simple and robust, allowing for an easy implementation of the technique and accommodates well with variations of drying conditions or presence of additives. [1] R. M. Parker, B. Frka-Petesic et al., Adv. Mater. 2018, 30, 1704477. [2] B. Frka-Petesic et al., Macromolecules 2015, 48, 8844. [3] B. Frka-Petesic et al., Adv. Mater. 2017, 29, 1701469. [4] B. Frka-Petesic et al., Phys. Rev. Materials 2019, 3, 045601.

Resume : The delicate interactions between cellulose and highly conducting nanocarbons, like graphene, have increasingly been exploited to develop composites with impressive electrical properties. However, since this research mainly has targeted nanoscale cellulose fibrils, these materials require significant leaps in processing technology development to achieve a justifiable production economy. In this work, a way to circumvent this obstacle is presented. By using electrotechnical pulp and mass-produced budget-graphene known as nanographite, a highly conducting yet easy-made paper has been developed for a papermaking processes. The forming mechanisms of this paper composite is believed to partly originate from an observed water-stable adhesion of nanographite flakes onto the fiber surfaces. The excellent electrical characteristics of this metal-free printable electronic paper, such as an in-plane conductivity of 107 S/cm and an areal capacitance of 9.2 mF/cm2, were successfully exploited in a printed electronics application.

Resume : Ultra-lightweight cellulose foams can be prepared by the foam forming of cellulose solution with surfactants. Foams have higher porosity and specific surface area than aerogels prepared from gel phase of cellulose solutions. However, the research is based on a cellulose solution which needs a solvent system to dissolve cellulose. Based on the simple mechanical stirring and solvent-free technique, it is critical to focus a research interest on the foam formation of cellulose nanofiber (CNF) which can be prepared in aqueous conditions. Moreover, the functionalization and the precise shape control of a foam-based printing ink will provide an extensive potential of CNFs for electronic and energy storage devices as well as biomimetic paper systems. In this investigation, polypyrrole is chosen for the functionalization of CNF foams because of its high conductivity and the mild conditions required for in situ polymer synthesis on the CNF surface. In addition, the biocompatibility of the CNF foam structures with living systems is discussed.

Resume : Transparent wood (TW) is a hierarchically structured anisotropic material produced by removing lignin and introducing polymer with a refractive index matching that of cellulose constituting the wood back-bone. The resulting TW material conserves the hierarchical complexity of native wood and most of its physical and mechanical properties. The TW is a birefringent material with high optical transmission and scattering. It can be used for different applications, from translucent building blocks to peculiar research objects, such as quasi-random lasers based on the TW doped with organic dyes or other optically active compounds. One of the important tasks for research of this material is development of reliable models that can predict the light propagation in the TW, based on different parameters, such as wood species, type of introduced polymers, and sample geometry. Multiple factors, such as inherent semi-ordering and overall structural complexity create difficulties for development of generalized models, first of all using analytical solutions [1-3]. Generic light behavior inside the transparent wood can be described using, e.g. a diffusion equation, that is applicable for cases when the propagation of light can be presented as a Markov process [4]. However, for precise description of electromagnetic optical effects, i.e. related to light polarization of coherence, such models are insufficient [5]. In this work, we report the FEM model (COMSOL) of light propagation in transparent balsa wood, and validate our results against experimental data of light intensity distribution after propagating through the TW sample. The model is also applicable to calculate an effective refractive index of the cellulose. Large scale SEM images of wood structure are implemented to build the model. We also demonstrated that ray optics approach can be used for computation of the light propagation providing the same result accuracy as the rigorous electro-magnetic numerical solutions implemented in COMSOL. References [1] Li, Y.; Yang, X.; Fu, Q.; Rojas, R.; Yan, M.; Berglund, L. A. "Towards Centimeter Thick Transparent Wood through Interface Manipulation," J. Mater. Chem. A, 6, 1094–1101, Dec 2017. [2] Chen, H.; Baitenov, A.; Li, Y.; Vasileva, E.; Popov, S.; Sychugov, I.; Yan, M.; Berglund, L. A. "Thickness Dependence of Optical Transmittance of Transparent Wood: Chemical Modification Effects," ACS Applied Materials & Interfaces 11(38), Sep 2019. [2] Vasileva, E.; Li, Y.; Vasileva, E.; Sychugov, I.; Menshi, M.; Berglund, L. A.; Popov, S. "Lasing from Organic Dye Molecules Embedded in Transparent Wood," Advanced Optical Materials 5(10), Mar 2019.

Resume : Giving paper new functionalities became a hot topic recently. We have been demonstrating that paper can be used not only as a substrate but also as the dielectric in devices based on semiconductor oxides, such as field effect transistors (FETs), memory transistors and CMOS like inverters. Nevertheless, many issues must still be addressed to optimize paper substrates to be used as dielectric in transistors, namely the sensitivity to variations in the relative humidity as well as its capacitance. Moreover, paper surface is rough turning into an enormous challenge the production of any electronic device on top of it. In this work we report different strategies been followed to address these challenges. Different cellulose sources (bacterial and vegetal) have been used as the basis to form paper like membranes that were then used as simultaneously as substrate and gate dielectric in a vertical transistor architecture with an amorphous IGZO as semiconductor. It was observed that the electrical performance of the devices is notoriously improved wen these cellulosic membranes are impregnated with ions from selected hydroxide solutions (LiOH, NaOH, KOH). It was shown that the infiltration procedure does not disrupt the initial structure of the membranes. The operation voltage of the transistors built on these infiltrated membranes is much lower when compared with non-infiltrated ones, being reduced from a VDS=15 V to less than 5 V, while the gate voltage narrowed for the range [-3;3] V. It was also observed that the performance of the devices is greatly improved when NaOH and KOH is used, either the field effect mobility obtained and the dynamic response of the devices for different frequencies. The ion enriched devices shown On-Off ratios that can of up to 5 orders of magnitude and saturation mobilities of close to 14 cm2 V-1 s-1. Steep subthreshold slopes of 0.2 V dec-1 were achieved in the smooth nanofibrillated cellulose membranes, supporting the existence of a good interface between the membrane and the oxide semiconductor layer.

Resume : The emergence of “green” electronics is a response to the pressing global situation where conventional electronics contribute to resource depletion and a global build-up of waste. For wearable applications, green electronic textile (e-textile) materials present an opportunity to unobtrusively incorporate sensing, energy harvesting, and other functionality into the clothes we wear. Here, we demonstrate electrically conducting wood-based yarns produced by a roll-to-roll coating process with an ink based on the biocompatible polymer:polyelectrolyte complex poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). The developed e-textile yarns display a, for cellulose yarns, record-high bulk conductivity of 36 Scm–1, which could be further increased to 181 Scm–1 by adding silver nanowires. The PEDOT:PSS-coated yarn could be machine washed at least five times without loss in conductivity. We demonstrate the electrochemical functionality of the yarn through incorporation into organic electrochemical transistors (OECTs). Moreover, by using a household sewing machine, we have manufactured an out-of-plane thermoelectric textile device, which can produce 0.2 μW at a temperature gradient of 37 K.

Resume : Inkjet printing is an additive manufacturing technique, widely used in research and upscalable to mass manufacturing. As a main advantage, for device production, does not require mechanical masks, where the pattern is produced directly in any type of substrate while printing, in a sheet-to-sheet or roll-to-roll method. Thus, it is a simpler and faster printing method for device manufacturing, allowing for pattern adjustments or corrections without increasing the production time. At the same time, being an additive manufacturing technique, it requires less ink and therefore, there is less waste, making it a more cost-efficient, environmentally friendly and versatile printing method, when compared to other printing techniques or even traditional microfabrication methods. It allows the use of different materials, such as organic or inorganic particles, in a wide viscosity range, allowing the manufacturing of a variety of devices or complex circuits, such as transistors, UV sensors, security tags, RFID antennas, among others. Biological inks are also possible to be manufactured, allowing a more accurate deposition of biological materials, for the development of biosensors or diagnostic platforms, for instance. Various substrates can be used, either rigid or flexible, with different properties, such as thickness, rugosity, porosity or surface activation. We have developed different inks, with different functionalities, in order to be deposited in various substrates, such as polymer, paper or cork substrates for printed electronics. Diverse active or passive devices have been inkjet printed, such as transistors, UV sensors, DMF chips or RFID antennas, on paper substrates. The easiness of pattern improvement together with the printing method capabilities, make inkjet printing a great tool for device manufacturing, using new materials and allowing different substrates exploration.

Resume : Sustainable and safe energy sources combined with cost effectiveness are major goals for society when considering the current scenario of mass production of portable and Internet of Things (IoT) devices along with the huge amount of inevitable e-waste. The conceptual design of a self-powered “eco-energy” smart card based on paper promotes green and clean energy, which will bring the zero e-waste challenge one step closer to fruition. A commercial raw filter paper is modified through a fast in situ functionalization method, resulting in a conductive cellulose fiber/polyaniline composite, which is then applied as an energy harvester based on a mechano-responsive charge transfer mechanism through a metal/conducting polymer interface. Different electrodes are studied to optimize charge transfer based on contact energy level differences. The highest power density and current density obtained from such a paper-based “eco-energy” smart card device are 1.75 W m−2 and 33.5 mA m−2 respectively. This self-powered smart energy card is also able to light up several commercial light-emitting diodes, power on electronic devices, and charge capacitors.

Resume : High abundance of cellulose sources in nature as well as developed technology of producing of the various derivatives of cellulose determine a relatively low cost of this polymer. Other advantages of this material are eco-friendliness, biodegradability, and biocompatibility. The microcrystalline cellulose can be easily incorporated with various dopants (e.g. inorganic micro/nanoparticles) due to the peculiarities of its crystal structure. Interaction between host and dopant (or filler) leads to formation of composites with useful properties. Such cellulose-based composites are attractive materials for elaboration of modern optoelectronic deviceslike flexible displays, luminescent coatings for light emitting diodes and solar cells, components of paper electronics, etc. In present study microcrystalline cellulose was used as host for zirconia micro/nanoparticles doped with europium(III) and fluorine (“cellulose+ZrO2:Eu,F”). The samples were characterized by scanning electron microscopy (SEM), luminescent and dielectric spectroscopies. Obtained samples of the composites possess interesting optical and dielectric properties those indicates interaction between host and fillers. The nanosized dopants usually incorporate into the amorphous part of cellulose that formed by microfibrils with weak internal bonding. In particular, the SEM studies have been showed that smaller nanoparticles of zirconia incorporate into cellulose plates when larger particles (above 100 nm) pierce out or located on surfaces of the plates. The effect of oxide particles on cellulose was observed on temperature dependences of dielectric permittivity of composites. The photoluminescence studies have been showed that part of absorbed excitation light energy is transferred from cellulose host to inorganic particles. The overall photoluminescence spectra of the composites studied significantly depends on the content of filler. Such composites can be used as luminescent coatings in lighting applications.

Resume : In this paper, we describe a novel 3D printed integrating sphere as a cheap alternative to those found on the market, this being made using a FDM 3D printer with PLA filament, for multiple applications such as food safety or greenhouse crop monitoring. The image acquisition system consists of the Raspberry Pi Zero, a high-performance minicomputer running the Linux operating system for embeded systems, an circular led array of LED’s (ranging from 365 nm to 940 nm), and a PinoIR V2 camera (camera for multispectral analysis with a resolution of 8 Mpixels). The image analysis is done using the MATLAB program. Images are taken in grayscale for each wavelength and then processed with different algorithms for image cleaning, element filtering, and edge detection. In the end, the images are recombined into a single image where the contaminants present in the sample to be analyzed are highlighted. Keywords: 3D printing, MATLAB, LED, multispectral analysis, Raspberry PI Acknowledgements: 393PED/2020, 87PD/2020, 18/N/2019, 19PFE/17.10.2018

Resume : We report the fabrication of gas sensors based on functionalized graphene with polyaniline, obtained by electrochemical polymerization of aniline on the surface of graphene. The morphological structure and properties of the sensors were characterized by scanning electron microscopy (SEM), Raman spectrometry. The sensor showed good electrical-resistance response toward carbon dioxide (CO2) at room temperature. An Arduino development board is used to monitor the temperature, humidity and CO2 level (commercial calibrated sensor). In addition to these sensors, the above-developed gas sensor based on functionalized graphene was also attached. The advantages of this sensor are high sensitivity, fast response time, short recovery time, and low power consumption. Keywords: graphene, functionalization, aniline, electrochemical polymerization, Arduino Acknowledgements: 393PED/2020, 87PD/2020, 18/N/2019, 19PFE/17.10.2018

Resume : Cellulose based materials are at the cutting edge of green electronic and photonic technology due to cellulose abundance and versatility. Besides batteries, supercapacitors, biosensors and others, the first ionic thermoelectric paper was recently made[1]. Based on this device, this work intends to use Molecular Dynamics in order to do a comprehensive analysis on the thermodiffusion of ions (sodium) interacting with modified cellulose fibers and compare it with the ion behavior in infinite dilution. For doing that, carboxymethyl cellulose fibers with two degrees of modification were analyzed at two ionic concentrations and in a range from 293K to 353K. For each system the sodium mean square displacement was computed, then the diffusion constant was obtained using the Einstein relation. Free energy perturbations and the Bennett Acceptance Ratio method were applied in order to evaluate the ion solvation free energy at different temperatures and therefore the Soret and Seebeck coefficients. The infinite dilution system was analyzed for several concentrations and simulation box sizes, those parameters did not affect the measured properties. The presence of cellulose fiber showed to interfere on ion behavior even from distances of ~3nm in all of the tested systems.

Resume : The natural ability of Cellulose Nanocrystals (CNCs) to self-organize into a chiral nematic liquid crystal phase with a helical arrangement that can be retained in dry CNC films, gives iridescent colors and interesting photonic properties. These properties include selective reflection and transmission of right- and left-handed circular polarized light (RCPL and LCPL, respectively). Due to the CNC rods’ negative zeta potential, owing from their acidic hydrolysis, electrophoretic deposition presents a viable method to obtain photonic CNC films on larger areas, when compared to conventional methods. The obtained films show the characteristic iridescence, with differences above 50% between transmission in RCPL and LCPL, inside the photonic band gap. Furthermore, structures with the ability to reflect in both, LCPL and RCPL channels, were studied, by using polypropylene tape as retardation plates. With this approach a great variety of colors in LCPL and RCPL can be obtained, depending on the number of layers, and initial photonic bandgap conditions. Possible applications for these films include photonics, anti-counterfeiting, stereoscopic imaging, sensing and in the realm of information processing.

Resume : Photolithographic defined films play an important role in modern optoelectronics and are crucial for the development of advanced organic thin-film transistors (OTFTs). Here, we explore a facile photoresist-free photopatterning method for natural carbohydrates and their use as OTFT gate dielectrics. The effect of the cross-linkable unit chemical structure on the crosslinking chemistry and dielectric strength of the corresponding films was explored by investigating cinnamate-functionalized carbohydrates from monomeric (glucose) to dimeric (sucrose) to polymeric (cellulose) backbones. UV-illumination of cinnamate ester of these carbohydrates leads to [2 2] cycloaddition and thus the formation of robust crosslinked dielectric films in the irradiated areas. Using propylene glycol monomethyl ether acetate as solvent/developer, patterned dielectric films with micrometer size features can be fabricated. P- and N-type OTFTs were successfully demonstrated using unpatterned/patterned crosslinked films as the gate dielectric and pentacene and N,N’-1H, 1H-perfluorobutyl dicyanoperylenecarboxydiimide (PDIF-CN2) as the p- and n-channel semiconducting layer, respectively. Our results demonstrate that natural-derived polymer gate dielectrics, which are soluble and patternable using bio-mass derived solvents, are crucial for the realization of a more sustainable OTFT technology

Resume : There are many examples of development of devices, which use materials elaborated on the base of cellulose. Those are sensors, drives, flexible electronics components, etc. However, cellulose and derived materials are not often used or studied as optical systems or systems where optical phenomena can be inquired. The development of solar radiation dosimeters consisting of an organic dye and titanium oxide as a photocatalyst printed on the cellulose substrate is one of the examples. Cellulose fibers containing specific luminescent compounds as markers and simultaneously as effective modifiers for textile products, papers and plastic is other example. The aim of this work was to develop micro/nanostructured composites based on microcrystalline cellulose (MCC) as matrix and oxide compound as filler. The essential advantage of oxide fillers is their stability. In this work we described the procedure of synthesis, manufacturing, structural and optical (luminescent) characteristics of the MCC – oxide composites made by cold pressing method. Simple oxides (ZnO, ZrO2) as well as complex oxides (BiPO4:Eu; K2Eu(PO4)(MoO4)) were incorporated into MCC matrix. Some carbon species (CNT, graphen, expanded graphite) were added to the composites as modifiers. Characteristics of these composites were compared to characteristics of similar compositions prepared on the base of nanocellulose. The morphological, structural and optical, especially luminescence, characteristics were studied that confirmed the perspectives of practical application of the composites under study. The correlation between structural, morphological characteristics and physical properties of composites was found and discussed. Obtained results confirmed the perspectives of practical use of the composites under study.

Resume : Our society is becoming more digitalized with a concomitant increasing demand for sustainable production of energy and materials. Filaments and fibers are important building blocks for many materials we see around us, such as textiles and non-wovens; found in clothes, packaging, diapers and composites. However, to be able to prepare the future interactive textiles, packaging materials and hygiene products it is necessary to expand the toolbox of electrically active filaments, while keeping sustainability in mind. Here we describe a new water-based colloidal process where cellulose nanofibrils (CNFs) are spun into interactive filaments. As long as the colloidal suspension has appropriate stability active materials, such as carbon nanotubes, graphene or conducting polymers can be mixed with the CNF. In this work conductive PEDOT:PSS polymer complexes were mixed with CNFs, to prepare filaments containing up to 40% conducting material. The electrical conductivity is controlled by the amount of incorporated PEDOT:PSS, up to 170 S/cm was achieved, still providing high mechanical properties from the CNFs; 19 GPa in modulus and 360 MPa in tensile strength. These filaments are highly interesting in materials where conductivity and mechanical performance are of importance. The number of such applications are vast (e.g. smart textiles, composites, as components in electrical devices), making this development an important step towards a green, digitalized future.

Resume : This work presents the development of electrochemical biosensors for monitoring analytes in sweat using a nano-fibrillated cellulose (NFC) paper. We incorporated electroactivity by adding poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) in the NFC paper. This electroactive paper follows an electronics-in-paper approach where the intrinsic nano-porous morphology enhances the electroactivity of the biosensors. Classification of electrochemical biosensors is according to the analytes or reactions they monitor: 1) direct monitoring of analytes or biological activity, and 2) indirect monitoring of inhibitors.[1] Direct monitoring involves detecting biomolecules that can either undergo redox changes within the electrochemical window or catalyze by an enzyme to produce electrical signals. Indirect monitoring uses the inhibition property of biomolecules to inhibit the electroactivity of a biosensor. Tracking the inhibition of electroactivity allows indirect monitoring of biomolecules. Human sweat contains many analytes such as dopamine, ascorbic acid, lactic acid, and cortisol. Analytes present in sweat exhibit a strong correlation with blood; thus, detecting these analytes can inform the physiological deviations from homeostasis.[2] Dopamine and ascorbic acid can oxidize within the electrochemical window, while lactate oxidase can catalyze lactic acid within the electrochemical window. Cortisol can bind to its antibody to form an antibody-antigen complex, which an electrochemical sensor can detect by its reduced electroactivity. This presentation will show sensitive detection of dopamine, ascorbic acid, lactic acid, and cortisol through direct and indirect electrochemical sensing approaches to demonstrate the broad biosensing capability of electronics-in-paper. The study will further encourage the scientific community to investigate on nano-porous effects of paper-based substrates. References [1] D. R. Thévenot, K. Toth, R. A. Durst, G. S. Wilson, Biosens. Bioelectron. 2001, 16, 121. [2] A. Hauke, P. Simmers, Y. R. Ojha, B. D. Cameron, R. Ballweg, T. Zhang, N. Twine, M. Brothers, E. Gomez, J. Heikenfeld, Lab. Chip 2018, 18, 3750.

Resume : Cellulosic products are sustainable solutions for a range of electronic applications owing to their inherent biocompatibility and molecular structure. One of their common uses is in the field of high-voltage insulation in various machines such transformers. Despite the common use of cellulose in high-field applications there are no quick and simple methods to test the electronic properties of different cellulosic materials in high voltages. This is due to the bulky nature of the test materials that necessitates the application of considerably high voltages (>200 V) for the investigations. In this study, we prepare thin films of cellulose that allow the investigation of the properties of cellulose, such as remnant polarization in cellulose i.e. ferro/piezo-electricity, and breakdown electric fields, using low voltage equipment. We resolve the limited presence of pin-holes in the cellulose films by forming a thin film of high-dielectric interlayer material. We show that it is possible to investigate the effect of high electric fields on cellulosic materials with simple lab equipment and applying low voltages (< 20 V). Using this technique, we study the dependence of the high-filed properties on cellulosic charge and the presence of various counter ions. Furthermore, we are able to investigate the role of humidity and the effect of using higher boiling point solvents in precursor cellulosic solutions.

Resume : Electrochromism is known as a modulation of the optical properties under an applied voltage. Used in various applications, aside to the commercialized smart windows based on transmissive electrochromic devices (ECDs), the opaque systems have received significant interest for displays purposes. More precisely, we recently demonstrated activation of Poly(3,4-ethylenedi-oxythiophene) PEDOT based ECD thanks to a cellular phone for use in anticounterfeit labels [1]. PEDOT based devices offer a color change from colorless or light blue depending on film thickness to dark blue. Herein, in a novel approach to increase the performance including color tuning, switching time, memory effect, processability, of EC devices, hybrid layers consisting of mixtures of PEDOT-based polymers and oxides, either EC active or inactive [2], are investigated. The integration of the hybrid layer in full EC devices based on paper will be discussed in respect of the choice of the paper substrate, the oxide-PEDOT mixture nature and composition, the printing process, the device architecture…. This activity included in the SUPERSMART project has received funding from the European Institute of Innovation and Technology (EIT). This body of the European Union receives support from the European Union’s Horizon 2020 research and innovation programme. [1] A. Danine et al., ACS Applied Materials and Interfaces 11(37), 34030, 2019. [2] D. Levasseur et al., Polymers, 11(1), 179, 2019.

Resume : In this presentation, we outline our work in the area of using direct laser writing to fabricate paper-based devices. This technique allows for rapid fabrication and prototyping of sensors, actuators, and electronics on commercial hydrophobic papers without the need for photolithography and etching processes.

Resume : Since the last decade, the development of Internet of Things (IoT) is exponential. It is estimated that the number of connected objects will be more than 22 billion in 2025. An application for IoT concerns the development of smart and connected packaging to ensure the conditions of the goods and to track them. Radio-frequency transparent devices can be considered as a relevant solution to answer this challenge. We propose here a solution to produce printed transparent antennas by using screen-printing process. Two key major aspects will be deeply discussed: (i) A cellulosic paper will be selected as substrate to decrease the carbon footprint of the device and to create flexible antennas. (ii) The second point will be dedicated to the design of the antenna itself. To be efficient and adapted, an antenna requires a high electrical conductivity of its pattern (< 1Ω.sq-1). The use of a conductive ink with a high solid content of silver particles enables to reach the targeted level of electrical conductivity at the expense of the optical transparency. To counterbalance this lack of transparency, this paper proposes several models of antennas including geometrical meshes based on square, honeycomb or diamond structures and thin lines (100 µm of width). With this method, the resulted printed antennas present an optical transparency of approximately 70% and their realized gain were preserved with a loss limited to approximately 0.35% in comparison with a conventional dipole.

Resume : Electronic waste (E-waste) is a huge concern all over the world, as one of the fastest growing waste streams in terms of both volume and environmental impact. Direct writing of laser-induced graphene (LIG) conductive patterns on biological substrates, and especially on wood, is a promising strategy to promote the development of environmentally friendly and sustainable electronics. However, the large-scale manufacturing of high quality conductive patterns remains challenging due to the complex nature of the surface of wood (inhomogeneous structure with variable chemical composition). Moreover, factors such as high ablation rates, the need of multiple lasing steps and the use of fire retardants are also limiting the applicability of conventional laser processes for the production of sustainable electronic devices. Here, we demonstrate a novel route for direct laser writing of LIG on wood and wood-derived materials (e.g. wood, paper). Our approach, which combines a fast CO2-laser treatment in normal atmosphere with a simple chemical pre-treatment of wood, allows obtaining highly conductive surfaces on both wood and wood-derived materials with unprecedented efficiency at large scale.

Resume : Laser induced graphene/graphite (LIG) is a method of converting a carbon rich precursor into highly conductive graphene using a laser. This method has shown great promise as a versatile and low-cost patterning technique. Here we show for the first time how an ink based on cellulose and lignin can be patterned using screen printing followed by laser graphitization. Screen printing is one of the most commonly used manufacturing techniques in printed electronics, making this approach compatible with existing processing of various devices. The use of forest-based materials opens the possibility of producing green and sustainable electronics and pre-patterning of the ink precursor enables carbon patterns without residual precursor between the patterns. We investigated the effect of the ink composition, laser parameters and additives on the conductivity and structure of the resulting carbon and could achieve record low sheet resistance of 3.8 Ohm/sq and a surprisingly high degree of graphitization. We demonstrated that the process is compatible with printed electronics and finally manufactured a humidity sensor which uses lignin as the sensing layer and graphitized lignin as the electrodes.

Resume : This talk will explore the new realm of using threads as an ultimate platform for flexible and stretchable devices. Threads offer unique advantages of universal availability, low cost, material diversity and simple textile-based processing. In this talk, I will report reel-to-reel fabrication to make functional smart threads for variety of sensing and electronics application. For example I will report on nanomaterial-infused smart threads for strain and temperature sensing. Threads will be presented for sensing pH, glucose, and other chemical biomarkers. Interestingly, threads also provide an ideal platform for passive microfluidic sampling and delivery of analytes. I will show our recent work on using this toolkit of thread-based microfluidics, sensors and electronics for application as surgical sutures and flexible smart bandages for chronic wounds. Our recent work on using threads for closed loop spatiotemporal dosage controlled drug delivery will also be presented. I will conclude the talk by providing an outlook on future research directions in the field of textile-based flexible bioelectronics.

Resume : Cellulose nanocrystals (CNCs) are lyotropic colloidal liquid crystals (LCs). They can easily be obtained from wood and other biomass, and typically have dimensions of 5-10 nm × 100-500 nm. When prepared with sulfuric acid, the CNCs are modified with sulfate half-ester groups that impart a surface charge and enable them to form stable colloidal suspensions in water. Owing to the large aspect ratio and inherent chirality of the CNCs, they can spontaneously form left-handed chiral nematic LC structures at low concentrations (~4 wt.%). Chiral nematic liquid crystals (CNLCs), also known as cholesteric LCs, are important for displays and other applications owing to their periodic helical structures. Responsive photonic crystals have potential applications in mechanical sensors and soft displays; however, new materials are constantly desired to provide new innovations and improve on existing technologies. To address this, we have developed a suite of scientific solutions based on the actuating and piezoelectric responses of CNCs and stretchable CNC-polymer nanocomposite systems. For instance, stretchable chiral nematic cellulose nanocrystal (CNC) elastomer composites can be prepared to exhibit reversible visible colour upon the application of mechanical stress. When stretched (or compressed) the colourless materials maintain their chiral nematic structure but the helical pitch is reduced into the visible region, resulting in coloration of the CNC-elastomer composite. By increasing the percentage elongation of the material (ca. 50–300%), the structural colour can be tuned from red to blue. Moreover, CNC-polymer nanocomposite films can be prepared in a straightforward manner to produce cost-effective stretchable piezoelectric materials (d33>50 pC/N) that outperform PVDF and some ceramics. We have meticulously documented the structure-property interrelations influencing these responses, and have examined concentration, pH, ionic strength, and electromagnetic field effects. Our presentation will detail these fundamental criteria and how they influence performance and functionality in select end-use application platforms.