Paper electronics: from materials to applications

Resume : In this work, the fabrication of Rochelle salt based piezoelectric paper is illustrated. Structures composed of paper and Rochelle salt are easily manufactured using simple processes. Both manufacturing and the material itself are environmental friendly. Additionally Rochelle salt is biocompatible. In the paradigm of a cleaner piezoelectric technology, the fabrication of active sensing or harvesting devices is developed. Thus processing method, material and piezoelectric properties have been studied. Actuating and sensing devices are reported in order to highlight the potential of this green piezoelectric material. Paper-based sensor and piezoelectric contributed recently to paper-based electronics development. In this work, the development of a fully biodegradable piezoelectric material has been addressed based on a method compatible with large area manufacturing at low-cost. We will first describe the fabrication of the composite material based on Rochelle Salt in solution. Characterization of the material’s and devices properties will be presented such as Young modulus, mass density, permittivity and piezoelectric characteristics. Examples of sensing and actuating applications, such as speakers and SAW devices, integrating printed metallic electrodes will be reported.

Resume : Сellulose is important for the production of advanced materials due to its abundance, multi-functionality, low toxicity of production and biodegradability [1]. The range of cellulose applications spreads from “paper electronics” to forensic examination and eco-friendly sorbents suitable for sorption and stabilization of a wide range of various types of materials. Variety of its properties (and as result applications) is determined by the porous, micro/nanostructure morphology of the cellulose host and by the unique nature of its interaction with other chemical compounds. The aim of this work was to fabricate using cool-pressing procedure the set of cellulose oxide micro/nanocomposite materials and to study their physical properties. The sets of composite like-to “ceramics” materials that consist of micro/nanocellulose and luminescent K2Eu(MoO4)(PO4) and ZrO2:Eu oxide particles were prepared. Composites were studied by means of scanning electron microscopy, XRD analysis, dilatometry, differential scanning calorimetry and thermogravimetric analysis, dielectric and luminescence spectroscopy. Dependencies of density, crystallinity, relative extension, thermal extension coefficient, dielectric relaxation parameters, intensity and shape of photoluminescence bands on temperature and content of oxide component were studied and analyzed. [1] K. Nelson, et al. American process: Production of low cost nanocellulose for renewable, advanced materials applications. Springer, 2016. p. 267.

Resume : Nowadays electrochromic devices, characterized by a reversible change in optical properties under an electrical stimulation, are present in various applications including smart windows, rear-view mirrors and more recently as a new functionality for electronic papers. Focusing on displays and in particular on the development of smart labels to fight counterfeit, we recently reported WO 3 based ECDs on paper substrate using a novel synthesis method involving UV- treatment [1]. Aiming at lowering the required activation energy, we further combined a simplified architecture type ECDs with PEDOT based materials. 4-layer ECD shows a nice reversibility and reflectance switch for a 0.7 V voltage window. Nevertheless, the color switch of such PEDOT based devices remain limited to blue. Following our initial investigations, herein the advantage of mixing oxides and polymers will be discussed in respect of achieving multi-color ECDs on paper substrate.

Resume : Paper based microfluidic devices have emerged as a simple and low cost platform for efficient clinical diagnostics. They are disposable, flexible, biocompatible, and require very less amount of fluid without any pumping equipment which makes them capable for diagnostics, especially in resource limited areas. Colorimetric detection is being employed using these devices; however, electrochemical detection is more sensitive and accurate, and can be easily miniaturized for integration with paper based devices. Cholesterol is an analyte that requires regular monitoring since its accumulation of cholesterol in blood leads to various heart diseases. Hence, in the present work, an effort has been made to develop a microfluidic cholesterol biosensor using paper based platform. Microfluidic channels were fabricated by patterning filter paper (Whatman 1) using photolithography. SU8 photoresist formed a hydrophobic barrier on the paper with microchannels of dimensions 1000 µm(w) x 100 µm(t). A three electrode system was fabricated by simple mask printing of graphite as working as well as counter electrodes and silver as reference electrode. The working electrode was modified using nickel oxide nanoparticles prepared using co-precipitation method. Cholesterol oxidase enzyme was spotted on the test zone and amperometric measurements were taken for different concentrations of cholesterol in the range 0.12-10.23 mM giving quick and sensitive detection.

Resume : Electrochromic devices are a class of color changing electrochemical cells studied for applications in reflective displays and energy saving dimmable windows/mirrors. As a substrate for future flexible electrochromic displays, paper is a mechanically robust, renewable option already proven compatible with large scale production and printing methods. Developing paper based electrodes that are not only highly conducting but also color neutral to ensure sufficient optical contrast and reasonable switching speed is currently a major challenge. The conducting polymer, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is a promising electrode material recently achieving conductivities approaching that of indium tin oxide after post-treatments with strong acids and polar solvents. Here, inkjet printing followed by a simple post-treatment with acid in ethylene glycol is used to generate patterned electrodes that achieve high conductivities of 1300 ± 100 S/cm on glass and a sheet resistance of 460 Ω/sq. on cellulose nanofiber coated paper while remaining color neutral (L*: 85, a*: -2.3, b*: -2.7). These electrodes support the redox switching of colored to colorless electrochromic polymers cyan, magenta, yellow and black allowing access to much of the perceptible color gamut. A lateral device based on patterned PEDOT:PSS pixels shows an 81% retention of charge after 9,000 cycles demonstrating practical viability of this approach for fabricating paper-based displays.

Resume : Graphene is a popular two-dimensional material that is lightweight, flexible and have high surface to volume ratio. Its large surface area in conjunction with thin, light and flexible nature triggered its use in energy storage devices, supercapacitors in particular. Integration of graphene to rather unconventional substrates such as paper certainly contributes to the development of paper-based supercapacitors. In this work, we fabricated paper-based graphene electrodes via brush painting of exfoliated expanded graphite. A conducting polymer, polypyrrole (PPy) was electrodeposited onto graphene electrodes to improve their electrochemical properties. Electrochemical properties of the fabricated PPy-graphene nanocomposite supercapacitors were then examined through cyclic voltammetry, galvanostatic charge-discharge cycles and electrochemical impedance spectroscopy. Fabricated paper based supercapacitor devices showed promising results with a specific capacitance of 94 F g-1 and remarkable capacity retention up to 91 % upon 5000 cycles. Our fabrication method is simple, environmentally benign, cost effective and can be easily scaled up.

Resume : Paper has been discussed and used in the past as a desirable omnipresent sustainable substrate material in organic electronics. However, in most cases the paper is covered with several barrier layers in order to generate impermeable flat surfaces that are needed for most common device architectures. However, paper comes in such a wide variety of different shapes, sizes and properties that one should consider to make the paper a functional part of an electronic device. It has been shown some time ago that simple craft paper sheets without any filler could be used as the transparent electrode in an organic solar cell. In this paper we use a sheet made of nano-fibrillated cellulose (NFC) as the transparent electrode in a similar device. The main difference lies in the surface roughness of the NFC sheet, which is much smaller than the surface roughness of a sack paper sheet. The NFC sheet has been made conductive by applying drop-casted silver nanowires. Conductivities comparable to standard transparent conducting oxide electrodes have been achieved. Bending of the NFC sheet based electrode did not change the conductivity. This transparent electrode was used as bottom electrode to build a photovoltaic cell based on organic semiconductors. The changes in the surface structure and surface roughness with each layer were investigated by atomic force microscopy. The electric characteristics of this device are presented, along with their optical properties, their surface physics and morphology.

Resume : Nanocellulose paper was produced with 3−15 nm wide cellulose nanofibers, and they exhibited both high transparency and highly smooth surfaces, while retaining the light weight and high foldability of conventional paper. Therefore, nanocellulose paper is one of the best candidate substrates for flexible electronics. In this presentation, we introduce their applications of future electronics such as nonvolatile memory, transistor arrays, organic solar cells, flexible antenna, and transparent conductive electrodes. Moreover, we also introduce the key parameters of developments for paper electronics.

Resume : Carbon dioxide (CO2), one of the most abundant substances on earth, is claimed to be responsible for the greenhouse effect that caused the increase of earth temperature. CO2 is naturally present in the atmosphere as a part of the earth's carbon cycle. However, CO2 is released through human activities, which keeps on rising and exceeding the ability of nature to recycling. CO2 could be managed as a raw material to produce added value products. CO2 has been used as a starting material for the synthesis of polypropylene carbonate (PPC), which is biodegradable aliphatic polyester and synthesized from copolymerization of CO2 and propylene oxide. In this work, we explored the use of PPC as dielectric and substrate materials for organic thin film transistors (OTFTs). Employing carbon dioxide based polymers, such as PPC, as electronic device materials not only help to boost the usage of CO2 feedstock and lower the utilization of fossil fuel raw materials but also reducing electronic wastes owing to their biodegradable ability. The PPC dielectric film exhibits smooth surface with the surface energy of 47 mN/m, dielectric constant of 3, leakage current density below 10-6 Acm-2 and excellent compatibilities with two p- and n-type organic semiconductors. Bottom gate top contact OTFTs were fabricated using PPC as dielectric, which exhibited good electrical performance with electron and hole mobilities of 0.14 and 0.026 cm2/Vs along with on-to-off ratios of 105 and 103, respectively, at the operation voltage of 60 V. The fabricated p- and n-type transistors were later connected to form complementary organic inverter working at VDD = 20V. Finally, we demonstrate the capability of PPC as a substrate by preparing flexible PPC sheet with the casting method. The fabricated PPC substrate showed the excellent transparency (in the visible region), sufficient mechanical property, and biodegradability. The fabricated OTFTs on PPC substrate reveal electron and hole mobilities of 0.27 and 0.28 cm2/Vs, respectively, with the on-to-off ratio of 104.

Resume : Printed electronics is a rapidly expanding research area, enabling low-cost, large-area, light-weight and flexible electronics for bendable integrated circuits. Concerning this, several printing technologies have been developed to accomplish these electronics requirements. Gravure printing, screen printing, flexographic printing, laser-induced forward transfer printing, and inkjet printing find extensive applications in stretchable electronics. Among these techniques, drop-on-demand inkjet printing is a very promising printing technique since it guarantees high resolution that allows selective deposition, in a non-contact process, of few picoliters amount of ink. Avoiding masks and vacuum systems, inkjet printing permits to attain fast prototyping of circuits, thus becoming a cost-efficient technology. Furthermore, inkjet printing can achieve, in special conditions, nanometric resolution by means submicron droplet ejectors or using self-alignment methods. Despite of the recent exciting advances in inkjet-printed multi-layered electronic components such as transistors, MIMs,[1] OLEDs and diodes, towards fully inkjet-printed electronic circuit, at present, for the electronics industry, inkjet-printed multi-layered devices are still unstable in air and have poor performances. Moreover, the present electronics applications require a high degree of reliability and quality of their properties. In order to accomplish these application requirements, hybrid electronics is fulfilled by combining the advantages of the printing technologies with the surface-mount technology (SMT). In this work, silver nanoparticles-based inkjet ink (AgNP ink) is used as novel approach to connect, by means capillarity, surface-mount devices (SMDs) onto inkjet-printed pads on paper substrate, conducted by inkjet printing technology.[2] [3] Excellent quality AgNP ink-junctions are ensured with high resolution picoliter drop jetting at low temperature (~ 150 °C). Electrical, mechanical and morphological characterization is carried out to assess the performance of the AgNP ink junction. Moreover, AgNP ink is compared with common benchmark materials (i.e. silver epoxy and solder). Electrical contact resistance characterization shows similar performance between AgNP ink and the usual ones. Mechanical characterization shows comparable shear strength for AgNP ink and silver epoxy, and both present higher adhesion than solder. Morphological inspections by field-emission scanning electron microscopy confirm a high quality interface of the silver nanoparticles interconnection. Finally, a flexible hybrid circuit on paper controlled by Arduino board is manufactured, demonstrating the viability and scalability of the AgNP ink assembling technique. [1] G. Vescio, J. López-Vidrier, R. Leghrib, A. Cornet, and A. Cirera, J. Mater. Chem. C 4, 1804 (2016). [2] J. Arrese, G. Vescio, E. Xuriguera, B. Medina-Rodriguez, A. Cornet, and A. Cirera, "Flexible Hybrid Circuit Fully Inkjet-Printed: Surface Mount Devices Assembled by Silver Nanoparticles-Based Inkjet Ink", Journal of Applied Physics 2017 in press. [3] J. Rivera, A. Peitivi, S. Llorente, J. Arrese, L. Servera, and A. Cirera, Patent ES 2 564 760 A1 (2014)

Resume : In the present work, we report a novel approach to the rapid prototyping of passive electrical components (resistors and capacitors) on plain paper by an additive technology consisting of supersonic cluster beam deposition (SCBD) coupled with shadow mask printing. Exploiting the high cluster beam intensity and collimation of SCBD, batches of resistors can be efficiently produced over a wide range of resistances. Parallel plate capacitors with paper as the dielectric medium were also produced with capacitance in the range of tenth of picoFarads. Since SCBD is an additive technique, components with different shape and dimensions can be produced while controlling independently the electrical characteristics. Simple circuits on paper can be easily assembled using the elements produced by SCBD; this approach opens the way to the rapid and cheap prototyping and integration of electrical components on paper as building blocks of more sophisticated systems for paper mechatronics.

Resume : In this work, we introduce a new concept of reusable eco-friendly electrolytes based on cellulose designed and engineered through a simple, fast, low-cost and eco-friendly dissolution method of microcrystalline cellulose, followed by the regeneration and simultaneous ion incorporation. The produced free standing cellulose based electrolyte films exhibit interesting properties for application in flexible electrochemical devices, like electrolyte-gated transistors (EGTs), owing to their high specific capacitances (4-5 µF cm-2). Indium-gallium-zinc-oxide (IGZO) EGTs on glass with laminated cellulose-based hydrogel electrolytes (CHEs) as the gate dielectric were produced presenting low working voltage (< 2V), showing an on-off current ratio (Ion/off) of 106, a subthreshold swing (SS) lower than 0.2 V dec-1 and saturation mobility (µSat) reaching 26 cm2 V-1 s-1. We also demonstrate flexible CHE-gated transistors on paper, which operate at switching frequencies up to 100 Hz. Combining the flexibility of the EGTs on paper with the reusability of the developed CHEs is a breakthrough towards biodegradable advanced functional materials allied with disposable/recyclable and low-cost electronic devices.

Resume : Paper-based electronics is an opportunity for the forest products industry (new markets with higher added value), that converges with societal requirements which call for smart yet low-cost and recyclable devices. Paper (or nanopaper) has been proposed as a substrate for printed electronics. Main applications include printed antennas, sensors or electromagnetic waves filters. Other exciting applications make use of paper as a working part of the electronic device (gate dielectric for flexible transistor, waveguide, chipless identification tags, etc.). The main limitation to the development of high frequency applications on paper is its high dielectric losses. In this literature review, we examine the origins of dielectric losses in paper materials in the THz domain. Structural effects in the sheet alter the propagation of electromagnetic waves. Fibre length and fibre orientation play a significant role at high frequency, and also cause indirect effects through modification of the pore size distribution. The major physico-chemical effect in the THz domain is sheet moisture. Mineral filler typically used for some paper grades show rather low intrinsic THz dielectric losses. Concerning chemistry effects, some data exist concerning the contribution of cellulose and lignin in the THz domain. Cristallinity of cellulose is shown to play a role in THz losses, by inducing characteristic absorption peaks. Needs for future research are highlighted. A systematic comparison of the contribution of wood constituents (cellulose, hemicelluloses, lignin, and extractives) is lacking, and must be assessed to select the right pulp source for paper electronics. The effect of mineral filler within the paper matrix must be identified to tune the papermaking process. The role of cations adsorbed on fibres during the papermaking process should be investigated. Several options to overcome the problem are suggested: (i) maintaining paper in a super-heated state, (ii) reducing diffusion losses by modification of paper structure, (iii) de-hydroxylation of cellulose, (iv) grafting fibres with a low loss polymer, (v) sheet impregnation with a low loss material. This will hopefully open new applications for paper materials and trigger new ideas for paper-based electronics.

Resume : Implementation of smart materials in large area devices requires scalable manufacturing. The use of paper-making techniques would offer an enormous production capacity, allowing for low-cost and large-scale manufacturing. In this work, we present a successful pilot-scale paper machine manufacturing of functional composite papers based on cellulose fibres and commercial tetrapodal zinc oxide microwhiskers. The functional paper was studied as photosensor, where we characterized its stability, sensitivity and speed. The devices show excellent photosensing properties over a wide range of light irradiances (0.01–1 Sun), including short response times (∼10 s) and long-term stability. Under simulated sunlight and a bias voltage of 1 V, small (0.5 cm2) the photosensor devices provided 12 μA photocurrent. To the best of our knowledge, this is the first example of pilot paper machine production of an optoelectronic paper, demonstrating the potential for large-scale paper manufacturing of active smart paper from low-cost industrial bulk materials.

Resume : In the present work, the manufacturing and characterization of a novel hybrid paper/ionic polymer material able to generate bending actuation in response to low voltage electrical stimuli is reported. Thin gold films (200 nm thick) are fabricated on commercial copy paper using physical vapour deposition, in order to produce conductive metal electrodes on both sides of the sheets. The metalized paper is impregnated with a solution of an acrylic acid-based ionic conductive gel, blended with imidazolium-based ionic liquid, and the imbibed paper is then exposed to low power UV light to photo-crosslink and integrate the polymeric compound into the fibrous support platform. This process does not significantly alter the conductive properties of the metal electrodes, as revealed by electrical testing, neither the mechanical properties of the paper, and eventually leads to the formation of the hybrid material. Electro-responsive actuators are obtained by simply cutting the processed paper into strips, which showed to undergo controllable and reversible bending deformation for applied voltages ranging from 1 V to 7 V, as a result of the ionic phase redistribution in the integrated paper/polymer system. The electrochemical characteristics of the hybrid material were monitored using impedance spectroscopy and cyclic voltammetry.

Resume : Recently a robust conducting paper composed of Poly(3,4-ethylene- dioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) and nanofibrillated cellulose (NFC) has been demonstrated. NFC-PEDOT is flexible, scalable and exhibits excellent electrical and mechanical properties. The superior mixed ion-electron conductivity of this paper promises a scalable bulk manufactory of supercapacitors which otherwise would not be possible using only PEDOT:PSS. In this report we do a systematic study of some key material parameters which determine the remarkable mechanical and electrical properties of this composite system. For this purpose, we use a range of PEDOT:PSS with varying conductivity, ionic purity and chemical stability. We also illustrate the direct effect of the chemical and morphological makeup of the cellulose material on device properties by using cellulose with varying charged groups and molecular weights to tune the power and energy characteristics of supercapacitors.

Resume : Citrus waste presents a vast potential for extraction of important compounds that can be used for various applications in nanotechnology and materials chemistry. In this research, we present the preparation of silver nanoparticles produced through reduction with hesperidin, a bioflavonoid extracted from orange peel (Citrus sinensis), with stabilization provided by nanocellulose, also isolated from this waste. The nanosilver size distribution is uniform (25.4 ± 12.5 nm) and particles are spherical in shape, being stable for several months. The system was characterized by Infrared Spectroscopy (FTIR), Transmission Electronic Microscopy (TEM), and Zeta potential measurements (-28.2 ± 1.0 mV). The nanosilver presented antimicrobial activity against Xanthomonas axonopodis pv. citri (Xac), a phytopathogen that affects orange plantations provoking the citrus canker disease, thus, producing heavy damages in the agricultural sector not only in Brazil but worldwide. Nanosilver bacteriostatic capacity was assessed applying Minimum Inhibitory Concentration (MIC) assays, and a concentration in the range of μg/mL was sufficient for bacterial growth inhibition. Additionally, we present the production of nanocellulose films doped with these silver nanoparticles for antimicrobial applications in membranes.

Resume : We propose a unique thermoelectric material based on a carbon-nanotube(CNT)-composite paper that a composite material of the CNT and a paper, i.e., "thermoelectric power generating paper." Recently, CNTs have been found to show a giant Seebeck effect. However, it is generally difficult to apply the CNT as a thermoelectric material because general forms of them are like powder and its high thermal conductivity is not suitable for the thermoelectric material. Generally, for the thermoelectric power generation, materials must have low thermal and high electrical conductivities. To solve this problem, we propose the use of a CNT-composite paper that we have already developed. It shows almost all functions of the CNT despite of the paper. Moreover, it shows low thermal conductivity because the pulp which is raw materials of the CNT-composite paper is thermal insulation material. For the purpose of this study, we firstly studied the optimum pulp amount that can keep the temperature difference between both sides of the sample. After that, we tried to find a suitable amount ratio of the CNTs and the pulps for our paper under the condition that the paper showed the low thermal conductivity. Finally, we tested the thermoelectric power generation using the CNT-composite paper. As results, we confirmed the thermoelectric power generation from the CNT-composite paper. In concrete, our unique "thermoelectric power generating paper" showed a few tens mW order of power.

Resume : Direct-write techniques have the ability to print user-defined patterns without the need of masks, screens or rolls, thus significantly reducing the production costs when manufacturing devices. As one of the most extended techniques inkjet-printing allows producing patterns by depositing single droplets on demand. In spite of its success, there are still some constraints, such as the range of printable viscosities (1-50 mPa·s) and the size of the particles in suspension (<1/100th of the orifice), that can limit the choice of the transfer material and the scope of potential applications. It is in instances like this that a technique such as laser-induced forward transfer (LIFT), since it is free from all those issues, appears as an appealing alternative. In LIFT a laser pulse is focused on a liquid layer of the ink to transfer, which is separated a convenient gap from an acceptor substrate. As the ink absorbs the laser radiation, a tiny fraction is propelled forward and a droplet is thus deposited. By the systematic repetition of this process any pattern can be transferred. In this work we prove the feasibility of LIFT for paper electronics applications. In order to determine the optimum printing conditions, we performed a systematic study of the main process parameters, such as the laser pulse energy and focusing conditions. With the aim of providing a proof-of-concept, we printed and characterized a fully functional gas sensor on a paper substrate.

Resume : In this study, we propose development of a “paper antenna” using carbon-nanotube(CNT)-composite-paper (CNTCP). We here focus on electrical properties of the CNT for our purpose. It is known that the CNT has high electrical conductivity. However, it is difficult to use the CNT because it is a nanoscale material. Therefore, some contrivance is necessary to use it, generally. As a solution, we have developed the CNTCP by mixing the CNT and paper as a composite material. The reason why we have chosen the paper is that the ordinary paper is a flexible and low cost material, and familiar to us. Therefore, if we can develop our “paper antenna” using the CNTCP, it is expected to apply to a wide area. Recently, contactless integrated circuit (IC) cards have been widely used. Generally, copper and aluminum are used for the antenna of the contactless IC cards. We consider that our CNTCP can be used as the antenna instead of those materials. In this study, we have succeeded to make a low-resistance-metallic-CNTCP. To develop a paper antenna, we need to make an antenna pattern on the CNTCP. For contactless IC cards, e.g., the loop antenna is used. Therefore, we chose the loop pattern for our CNTCP antenna. We here try to make a loop antenna pattern on our CNTCP by some cutting methods, and measure and evaluate the operation of our paper antenna. We believe our paper antenna will be applied to various objects in our daily life in near future.

Resume : We propose an unique solar cell, i.e., a paper dye-sensitized solar cell(DSSC) based on a carbon-nanotube(CNT)-composite paper(CP). Nowadays, because of recent environment problems, clean power generation(CPG) has been attracting much attention. We here focus on solar cells for the CPG. As the targeted device, we study the DSSC. Commonly, it consists of conductive and dye-absorbed-semiconducting(SC) electrodes facing each other. Also, an electrolyte is poured between two electrodes. For our DSSC, a metallic(M)-CNT-CP for a conductive electrode and a SC-CNT-CP with dye for a dye-absorbed-SC electrode are used, correspondingly. By using the following method based on the Japanese washi papermaking method, the M- and SC-CNT-CP can be fabricated easily. In the beginning, a pulp suspension is prepared by dispersing pulps in water. At the same time, a M- or a SC-CNT suspension is prepared. Then, above two suspensions are mixed. Next, fibers is scooped up from the mixture by wire netting and dried them by a heating press. We have clarified that our paper-DSSC has been able to be fabricated and generate power so far. However, its conversion efficiency has not been enough yet. We here try to overcome its low power generation problem by studying and improving its structure, used chemicals, dyes, and so on. As a first step, we apply a grid electrode on the SC-CNT-CP electrode for efficient current collection. Thus, the efficiency was 1.5 times better comparing with the previous one.

Resume : Paper has assisted the development of human civilization for millennia enabling knowledge transfer. Nowadays, the use of paper has gone beyond printed information towards electronic devices. While paper electronics is challenging due to paper’s highly porous framework and surface roughness, energy storage devices can benefit from these features. Furthermore, paper can enable lightweight and environmentally friendly Li-ion batteries. Here, we show that a common inkjet printer can be used to dispense aqueous inks containing battery’s active materials on paper. In addition, in this configuration, paper is also used as the separator. We used commercially available materials, focusing on lithium titanate (LTO)-based anodes and lithium iron phosphate (LFP)-based cathodes to exemplify the inkjet-printed paper battery concept, performances and feasibility. The LTO/LPF chemistry is well known and commercial solutions are available for an extensive range of energy storage systems. The developed inkjet-compatible aqueous ink formulations containing active materials are stable and allow continuous printing for more than 1 hour. The paper electrodes were first evaluated in a half-cell configuration, showing stable cycling at different cycling rates. The active material load can be adjusted with the number of prints. For example, 10 prints are required for a load of 1 mg/cm2. Full LTO/LFP cells using paper as separator are fabricated by printing on both sides of the paper (275 g/m2). These inkjet-printed paper batteries can meet the requirements of numerous size- and shape- sensitive applications. In addition, paper can facilitate battery recycling that currently relies on exhaustive metallurgical processes.

Resume : In the present day flexible display industry, the popular packaging approach engages a so-called anisotropic conductive adhesive film (ACF) technology. Advanced microelectronics packaging using anisotropic conductive film (ACF) is a low-temperature, fine-pitch interconnect solution that exhibits an attractive alternative to solders in many applications, such as chip-on-glass, chip-on-board and chip-on-flex. Conventional ACFs are composed metallic microparticles or metal-coated polymer balls randomly dispersed in a polymer glue of 5-20% particle distribution. However, as the pitch between bonding pads is getting smaller, lateral leakage between electrodes becomes problematic due to the connecting of those useless conductive particles. Furthermore, in the case of flexible printed circuit (FPC) boards, the process temperature during compression is limited and a lower bonding temperature is desirable. Here, we propose a novel method for decreasing the lateral leakage issue in small pitch bonding pad on circuit and it will improve the reliability of package in next generation product. In this work, we investigate the application of microstructures in improving electrical contact between bonding pads on display panels and IC boards or FPC boards. We demonstrate a kind of microstructures, directly plated Au micro-pillars on electrodes that will be attached on the bonding pads of circuit boards. The drawing illustration as shown in Fig. 1 are the fabrication process of Au micro-pillar structure and the modules of Au micro-pillars to withstand in non-conductive film for the bonding between ITO glass and Flexible IC chip. In this study, we will describe this Au micro-pillar from its fabrication to the structural and electrical characterization and the application in flexible circuit.