Advanced materials for printing

Resume : Paper electronics is rapidly evolving and the possibility of extending the available information beyond the printed graphic is very interesting [1]. Many of the suggested approaches are for example to improving logistics or disposable sensing, e.g.as food sensors on packages to minimize food spoilage. However, for paper electronics to be truly recyclable and/or disposable the components need be environmentally friendly and bio-compatible, and preferably operating at low voltages. Here we propose an environmentally safe approach to such active circuits and electronic functionalities, by making ion-modulated transistors on paper. By blending the semiconductor poly(3-hexyl thiophene) (P3HT) with a biodegradable poly-lactic acid (PLLA), and using solidified ionic liquids (ILs) tocreate solution-processable deep eutectic mixtures that areliquid or semiliquid at room temperature wehave created printable transistor structures and logic circuits operating at ~1V [2,3]. The use of the transistors in paper electronics based sensing applications for biologically relevant systems will be discussed and presented. References [1] D. Tobjörk and R. Österbacka, Advanced Materials, 23, 1935-1961 (2011). [2] F. Pettersson, J. Koskela, T. Remonen, et al.,MRS Communications 4, 51-55 (2014). [3] F.Pettersson, T. Remonen, D. Adekanye, et al.,ChemPhysChem 16, 1286-1294 (2015)

Resume : Transparent conductors films (TCFs) are essential components in many optoelectronic devices. Indium tin oxide (ITO) has been widely used in TCFs due to its low sheet resistance and high visible light transmittance. However, the brittleness and rarity have restricted the application of ITO in flexible electrical devices. Metallic nanowires (NWs), like Ag NWs or Cu NWs, have become a promising alternative solution by forming a network structure on a transparent substrate. Although Cu is much cheaper than silver, oxidation of Cu NWs become a critical issue for electrical conduction and structure integrity considerations. In this study, Cu NWs were synthesized by pulsed electrodeposition with porous anodic aluminum oxide (AAO) templates. To improve their anti-oxidation property, a thin layer of silver was coated on the Cu NWs in a silver nitrate solution at room temperature through a galvanic replacement reaction. A filtration coating approach was used to fabricate the TCF with Cu-Ag NWs. We develop a thin film transfer process to embed the NW network in PMMA matrix, which not only provides a strong adhesion to the flexible substrate but also reduces the NWs contact resistance with an effective sheet resistance down below 10 Ω Sq-1. The study shall help the development of NW-based TCF technology for flexible electronic devices.

Resume : Chemical solution deposition (CSD) offers a versatile and low cost methodology for the production of coated conductors; however, reaching thick films (~1μm) by CSD becomes a great challenge due to the high stress produced during pyrolysis treatment, which may lead to buckling and crack formation and then decreasing the superconducting properties. Particularly, piezoelectric Inkjet printing (IJP) is presented as a robust and scalable technology to deposit by CSD YBa2Cu3O7 (YBCO) thick films starting from Y, Ba and Cu metalorganic low Fluor solutions with drop on demand single and multinozzle printheads. Ink formulation has been tuned using additives (i.e. diethanolamine, polyethylenglycol) to adapt the physicochemical and rheological properties to the printhead characteristics (viscosity, surface tension, solvent evaporation rates…) and also to control the interaction with the substrate (wettability, liquid distribution, drop fusion…) in order to obtain homogeneous and reproducible high performance YBCO films. In addition, these additives give toughness to the system avoiding defects during the pyrolysis treatment. We have performed an in-situ study (optical microscopy, interferometry) of the different stages during pyrolysis of the deposited films whose decomposition of the organic matter is identified by thermogravimetric, infrared spectroscopy and mass spectrometry analysis. All together our analysis has allowed defining the optimal heat treatment to prepare thick YBCO films.

Resume : For a decade, solution-processed functional materials and various printing technologies have attracted increasingly the significant interest in realizing low-cost flexible electronics. In this study, we report the preparation of highly conductive metal nanoparticle inks which can be successfully printed onto polymeric substrate and controlled the line width of printed inkjet-pattern. Cu nanoparticles were synthesized via the chemical reduction of Cu ions under inert atmosphere. To prevent interparticle agglomeration and surface oxidation, oleic acid was incorporated as a surface capping molecule and hydrazine was used as a reducing agent. To endow water-compatibility, the surface of synthesized Cu nanoparticles was modified. For reducing the surface tension and the evaporation rate of aqueous Cu nanoparticle inks, the solvent composition of Cu nanoparticle ink was investigated in the range of 30~70wt% of DI water with constant ratio of water mixable solvent. The effects of DI water content as a dispersion medium on rheology and solid concertation of aqueous based Cu nanoparticle ink for inkjet printing were investigated. The 40wt% aqueous Cu nanoparticle inks with 0.9wt% of dispersant showed the “Newtonian flow” and had a low viscosity under 10mPa∙S, which was applicable to inkjet printing. The line with of printed Cu patterns was controllable by the dispersion medium. The Cu patterns with a line width of 40~60㎛ were successfully fabricated, and which were depended on water content of dispersion medium. The 60wt% aqueous Cu nanoparticle ink was prepared with “Newtonian flow”. The resistivities of Cu patterns are measured to be ~10μΩ∙㎝ at annealing temperature of 300℃. (Ref.; Sunho Jeong et al., Langmuir, 2011, 27 (6), pp 3144–3149)

Resume : Recently the implementation of solution-processed or printed inorganic semiconductors, such as zinc oxide (ZnO) is becoming a real alternative in printed electronics to organic semiconductors regarding chemical stability, switching speeds and mobility. In addition, their implementation in electrolyte-gated transistors (EGTs) open the way to the development of fully-printed devices, which can operate at low voltages owing to the use of high capacitance electrolytes. The ultimate goal is to move towards ultra-cost-effective, flexible and environmentally friendly electronic devices, embracing green electronics for a sustainable environment, as demanded by modern society standards. We report the development of a fully-printed and flexible inorganic EGTs on paper substrates. The channel of the devices is based on ZnO nanoparticles blended in ethyl cellulose. The devices besides low operation voltages (-2 to 4 V), displayed n-type behavior with a subthreshold swing of 0.11 Vdec-1, a saturation mobility of 0.08 cm2 V-1s-1 and an on/off ratio of 6.70x103. Investigation in this field could potentiate effective roll-to-roll fabrication of printed logic circuits, showing huge implications for industrial printing standards. In the near future, we foresee this technology to be omnipresent in a wide range of applications, reaching from smart packaging to wearable electronics owing to the present proof-of-concept of a fully-printed inorganic EGT.

Resume : With the discovery of electrically conductive polymers (ECPs) an attractive object of research has begun. ECPs combine the electrical properties of metals with the advantages of plastics (flexibility, lightness, stability, etc.). Among them polyaniline (PANI) is unique for its high thermal and environmental stability, ease of synthesis and interesting redox properties. The combination of electrical conductivity and tunable processability of PANI make this polymer particularly tempting for application in numerous sectors, included printing processes. Even though many methods have developed to synthesized PANI of good quality in terms of conductivity, stability and solubility, all these approaches are based on the use of toxic stoichiometric oxidants (typically metals in high oxidation state) and lead to the production of carcinogenic coproducts (i. e. benzidine). In line with the growing environmental sensitivity and the necessity of clean products, we have recently addressed our efforts on the development of environmentally friendly protocols to produce “green” PANI. Herein, we report a brief overview of the state of the art on the PANI synthesis by environmentally friendly approaches, our results in the PANI preparation by clean processes and our recent goals in their used for printable PANI-based inks fabrication. The electronic, chemical and physical properties of printed devices will be also discussed.

Resume : A single graphene layer can absorb 20% of microwave energy [1] and a sandwich structure of six graphene layers separated by 100 nm thick PMMA layers already absorbs 50% [1]. Based on this fact we developed an easy to use, cheap, 3D printing process for producing complex 3D structures made from a nanocarbon-plastic composite fibre and a pure plastic (PLA) fibre. The 3D printing process makes it possible to fabricate devices with predefined BRDF (Bidirectional Reflection Distribution Function) and BTDF (Bidirectional Transmittance Distribution Function). Indeed, by applying ordered and disordered dielectric protonic crystal structures one can realize tailor-made BRDF functions [2], adding lossy material to the structure, however, makes it also possible to precisely define the BTDF function. We demonstrate this approach by creating an antireflection layer, which, besides its low microwave transmission minimises the reflection by introducing an appropriate nanocarbon concentration gradient. Theoretical calculations convincingly explain the measured electromagnetic absorption and transmission data in the GHz domain. 3D printing of nanocarbon containing microstructures offers a flexible and cheap technology to produce complex structures with tuneable electromagnetic characteristics, which provides a new route for microwave filters, absorbers, and sensors. 1. K. Batrakov et al, Scientific Reports 4 (2014) 7191. 2. G. I. Mark et al, PRB 80 (2009) 051903.

Resume : With the popularity of flexible electronics, applications of stretchable or wearable devices require advanced electronic materials, which exhibit excellent mechanical robustness and electronic functionality at high strains. This is of special interest for the fabrication of conductive tracks, which are used as interconnects for such devices. One of the most significant hurdles to achieving stretchable conductive tracks using conventional materials , e.g. metallic nano-structures, arise from their intrinsic limitations like poor mechanical stretchability. As an alternative, carbon nanotubes (CNTs) offer outstanding electrical and mechanical properties. Especially, when CNTs are deposited as thin films, they provide superior mechanical stretchability. In addition, CNTs can be formulated as inks and adapted for different printing processes, e.g. inkjet printing. In our study, we fabricated conductive tracks, composed of monolithically inkjet-patterned CNT films on polymer substrates, and we investigated the relationship between printing process, film morphology and their electro-mechanical properties. Experimental results have shown that, those films offer excellent mechanical and electrical properties. They show excellent mechanical stretchability up to 50% of tensile strain without significantly degrading their electrical performance, and outstanding mechanical durability up to 1 million cycles at a strain amplitude of 2%. Those promising properties of CNT-based conductive tracks will benefit the production of high-performance stretchable electronic devices.

Resume : Inkjet printing is a promising manufacturing route for the production of large area and low cost flexible electronics. Recently, graphene, which is a monolayer of sp2-bonded carbon, has been considered as a potential candidate to replace metallic conductors in printed devices due to its remarkable mechanical, electrical properties. Graphene inks based on pristine graphene flakes or reduced graphene oxide (rGO) formed by liquid phase exfoliation (LPE) have been printed for electronic applications, such as transistors, conductive electrodes, chemical sensors, and radio frequency devices. However, the size of graphene or rGO by LPE method in previous work is in a relatively small mean graphene flake size, typically < 1 µm. Such small flake size will increase the number of inter-flake junctions in any conductive pathway, which will reduce the conductivity of a printed graphene film to below that of CVD grown graphene or of mechanically exfoliated graphene sheets. Here, we present a holistic approach to produce highly conductive printed rGO patterns through oxidization of graphite, liquid exfoliation of graphite oxide (GO), ink formulation, inkjet printing, and final reduction. We have produced large GO sheets with diameter up to 200 µm using the improved Hummers method. Such large size GO sheets can be successfully ejected to form stable droplets through a 60 µm nozzle, which is significantly smaller than the largest GO flakes in the ink. These large flake inks can be used to print stable linear and 2D features after drying. After reduction, the rGO pattern shows conductivity as high as 2.51 × 10^4 S/m for processing temperature lower than 100 °C. In addition, we produced a fully printed flexible humidity sensor by using rGO as the electrode and GO as the sensor layer on plastic substrate.

Resume : The conductive ink and paste business is a large market that is expected to grow to $2.87 billion by 2025,1 comprising nanometal inks (silver, copper), conductive polymers and carbon-based inks. Nanometal inks are high cost2 (silver: $550/kg; copper: $7.4/kg on average during 2014), requiring high temperature sintering to remove polymeric stabilizers,3 and have high specific gravity which leads to reduced stability upon storage.3 Nanometals also suffer long-term oxidation.4 Conductive polymer inks are limited by their solubility, stability, and processability.3 Graphene, however, can be exfoliated5-7 from highly abundant, low cost2 graphite ($1.5-2/kg on average during 2014).Furthermore, the electrical, mechanical and thermal properties of graphene combined with its high surface area,7 make it highly desirable for electrodes in energy storage devices.8Here, we use a scalable microfluidic processing route to exfoliate graphite in water-surfactant solutions. Graphene nanoplatelets (GNPs) with lateral size ~1 µm and thickness ~10 nm, are produced at loadings >50 mg/mL. These are significantly higher than current graphene production routes (sonication5 or shear mixing9) that afford low concentrations of few layer graphenes (<0.1 mg/mL) following additional centrifugation steps to remove the non-exfoliated particles.5,9The ink rheology is tuned using sodium carboxymethyl cellulose over the range of 1 1800 cP, so that roll-to-roll flexographic and screen printing can be achieved. The high GNP loading affords high conductivities when printed(~2.2 Ω/□ @ 25 µm thickness; 2 x 104 S/m), essential for fast charge/discharge rates in energy storage devices.8 In this context, we demonstrate screen and flexographic printed electrodes on plastic for flexible supercapacitors with an areal capacitance of 10 mF/cm2 with 5 µm thick electrodes, comparable to state of the art flexible planar supercapacitor electrodes.10 [1] K. Ghaffarzadeh and H. Zervos, Conductive Ink Markets 2015-2025: Forecasts, Technologies, Players. IDTechEx, 2016 [2] US Department of the Interior and US Geological Survey, Mineral Commodity Summaries 2015 [3] A. Pekarovicova, Recent Advances in Electrical Engineering and Computer Science, 13-21 (2015) [4] S. Magdassi et al. Materials, 3,4626-4638, (2010) [5] Y|. Hernandez et al. Nature Nanotechnol.3, 563-568 (2008) [6] F. Bonacorso et al. Materials Today, 15, 12, 564, (2012) [7] A. C. Ferrari et al. Nanoscale7, 4598 (2015) [8] F. Bonacorso et al. Science, 347, 6217, (2015) [9] K. R. Paton et al. Nature Materials 13, 624 (2014) [10] Y. Shao et al. Chem. Soc. Rev.,44, 3639-3665 (2015)

Resume : We report fully-printed top-gate-bottom-contact organic thin-film transistors using substrates prepared from cellulose nanofibers and commercially available printing inks to fabricate the devices. Gravure printing was used to coat the substrate with a polymer resist to decrease the surface roughness and close the surface. Transistor structures were fabricated using inkjet printing for metal-based conductors and gravure printing for the polymer-based dielectric and semiconducting layers. The maximum processing temperature was 120 °C. The obtained transistor performance is compared to that of similar sheet-to-sheet and roll-to-roll printed transistors on plastic substrate in terms of mobility, threshold voltage, on/off ratio, and bias stress stability.

Resume : We realize on the advanced control of straightforward fabrication of an organic thin-film pattern using digitally-controllable organic vapor-jet printing (D-OVJP) method, in which deposition of organic materials is controlled point by point in a digital manner by producing a jet of organic vapor in a pulsed mode only on demand. The D-OVJP can utilize all the benefits of the current OVJP technology which combines the advantages of both (i) a conventional evaporation method such as use of well-established, sublime-grade small molecules resulting in high performance and long-term reliability and (ii) ink-jet printing technology such as mask-less pattern formation and a good scalability. In D-OVJP system, the “jet-on-demand” type operation can be possible in a straightforward manner through the change of input digital signals, implying the number of the pulses and/or to the duty ratio of the digital signal. By utilizing the full advantages of D-OVJP method, the point-by-point control of conductivity of doped organic semiconductors can be realized, which can give an enhanced performance of printed electronic devices with organic materials. We will also present some device applications based on the localized control of the concentration of dopant molecules at the co-deposition system by using D-OVJP method.

Resume : We suggest a novel method of fabricating water-borne colloids of semiconducting polymers for use in environmentally benign processes involving organic electronics, without compromising the high charge carrier mobility of the polymeric semiconductors. Non-ionic surfactants were utilized as a key material to fabricate aqueous colloids of semiconducting polymers via a miniemulsion process. By developing smart surfactant engineering techniques, we could selectively remove non-ionic surfactants after film deposition, rendering efficient inter-particle charge coupling. We introduced such non-ionic surfactants-technique onto a donor-acceptor type polymeric semiconductor with an inherently high charge carrier mobility, resulting in a high-mobility (~2.51 cm2/ V s) water-borne polymer field effect transistor for the first time

Resume : Metallic nanowires (NWs) such as silver and copper NWs have been dispersed on polymer substrates serving as transparent conductive films to replace the predominant indium tin oxide (ITO) films in flexible electronic devices. Although Cu NWs have desired cost advantage, oxidation is the detrimental issue associated with Cu NW fabrication process. It was hypothesized that the oxidation resistance could be improved by coating an inert metal on Cu NWs to form an oxidation barrier layer. In this study we intend to improve both oxidation resistance and mechanical strength through introducing dense nanoscale twinning structure in cupronickel NWs. First, nanotwinned Cu NWs were synthesized using porous anodic aluminum oxide (AAO) templates by pulsed electroplating. After the nanotwinned Cu NWs were released from AAO templates by a wet chemical method, they were coated a thin layer of Ni using a low-toxicity reducing agent, sodium borohydride, in ethylene glycol solvent. A microstructural and compositional analysis has been conducted on the cupronickel core-shell structure by transmission electron microscopy. The temperature-dependent oxidation characteristics of single cupronickel NW was investigated by monitoring the evolution of electrical resistivity in ambient using a 4-point method. Moreover, the cupronickel NWs were embedded into PMMA through vacuum filtration method and pressing process. The NW contact resistance is greatly improved by the pressing process. The NW embedded transparent film has achieved a low sheet resistance of 16 Ohm/sq. The study shall help the development of low-cost transparent conductive films using Cu-based NWs.

Resume : In this study, we report about the laser synthesis and characterization of the gradient core–shell HTS covered with polycarbonate and/or polyesterketone shells of ultra-fine particles and layerwise selective laser melting of the 3D samples. The optimal regimes of such synthesis are being discussed. Optical and scan electron microscopy with EDX, X-ray diffraction studies show that both core–shell systems have a complex structure with interesting electro-physical properties. Expanding computer aid design of the SHTC core distribution in polymer matrix opens door to manipulate of electromagnetic field distribution within such 3D complex core-shell samples. Keywords: selective laser melting (SLM); high temperature superconductivity (HTS), core-shell structures, polycarbonate, polyesterketone.

Resume : Carbon nanotubes (CNTs) constitute a unique class of materials with a wide range of applications. The sp2 chemical bonding of carbon atoms provides exceptional electronic, thermal and mechanical properties [1, 2]. With proper solvent, surfactant or stabilizer chemistry, CNTs can be dispersed with different binders to produce inks that can be used with various printing methods (screen printing, aerosol jet printing, transfer printing, contact printing) [3]. Screen printing offers a fast, economic and potentially large scale method for the deposition of carbon nanostructures on a wide range of substrates. This technique is already used for the deposition of conductive, resistive and dielectric layers in the fields of photovoltaics, hybrid integrated circuits, energy storage, automotive and electrochemical sensors [4]. In this work, screen printed multi-walled carbon nanotubes (MWCNTs) are deposited as thick films by forcing a high viscosity ink through a 2.5x2.5 (mm) open area on a 90 T polyester mesh with a squeegee [5]. The rheological and dielectric properties of the films have been modulated through different combinations of binders, solvents, inks? additives and MWCNT concentration. MWCNT powders, inks and films are characterized by FESEM, Raman spectroscopy, thermal analysis, and sheet resistance measurements. Thick films comprising different types of MWCNTs are integrated in printed patch antennas and slot ring resonators fabricated on commercial substrates (FR4, Arlon) to investigate the tuning of their resonances at microwave frequencies. It is observed that the MWCNT films essentially present a constant surface resistance (or conductivity) but a varying capacitive reactance that is responsible for tuning the circuit or antenna in which the film is embedded. The ring resonator exhibits higher sensitivity to tuning in the WLAN band (2.4 GHz) than the patch antenna which is resonant in the X-band (8 GHz). Results from electromagnetic simulations as well as microwave measurements will be presented at the conference. References [1] H. Dai, ?Carbon Nanotubes:Synthesis, Integration and Properties,? Accounts of Chemical Research, vol. 35, no.12, pp.1035-1044, 2002. [2] T.E. Chang, A. Kisliuk, S.M. Rhodes, W.J. Brittain, A.P. Sokolov, ?Conductivity and mechanical properties of well-dispersed single-wall carbon nanotube/polystyrene composites,? Polymer, vol. 47, pp. 7740-7746, 2006. [3] C.S. Jones, X. Lu, M. Renn, M. Stroder, W.-S. Shih, ?Aerosol-jet-printed, high-speed, flexible thin-film transistor made using single-walled carbon nanotube solution,? Microelectron. Eng., vol. 87, pp. 434-437, 2010. [4] X. Cao, H. Chen, X. Gu, B. Liu, W. Wang, Y. Cao, F. Wu and C. Zhou, ?Screen Printing as a Scalable and Low-Cost Approach for Rigid and Flexible Thin-Film Transistors Using Separated Carbon Nanotubes,? ACS Nano, vol. 8, no. 12, pp. 12769-12776, 2014. [5] Y. Zhou, L. Hu, G. Grüner, ?A method of printing carbon nanotube thin films,? Appl. Phys. Lett. , vol. 88, pp. 109-123, 2006.

Resume : A novel approach of using layer by layer reactive inkjet printing of regenerated silk fibrin was used to generate micron-sized silk rockets which have the enzyme catalase immobilised inside the scaffold structure and use catalase to drive their motion in samples containing H2O2. We show that it is possible to digitally define the enzyme distribution within the rockets and alter their trajectory behaviour accordingly. This technique has great potential to easily incorporate different enzymes, proteins, chemicals or other biomolecules and build versatile devices. Small scale devices that can generate thrust via catalytic reactions within fluidic environments have potential applications including environmental monitoring and remediation, in vivo drug delivery and repair, and lab on a chip diagnostics. Current manufacturing processes of such devices often use slow and lengthy production processes (e.g. evaporation) combined with expensive materials such as platinum. The location of catalyst on these devices has been shown to influence trajectory behaviour but is not easy to control using conventional methods. Devices using e.g. platinum as a catalyst can undergo biofouling thus inhibiting their catalytic reaction. By using biocompatible silk scaffolds created by reactive inkjet printing the devices generated have the potential to overcome all these problems.

Resume : Fabrications of organic field-effect transistors (OFETs) based sensors have attracted immense attention for monitoring health and wellness parameters and other medical applications due to the capability to easily integrate into the main electronics with multi-parameters analysis to derive the physiological parameters of interests. In addition, such devices can be fabricated on transparent, stretchable and ultra flexible substrates for large area measurements. In this work, we are going to present how the polarization of gate dielectric layer can be exploited to fabricate temperature sensors, which is highly sensitive to temperature within ?30oC to 80oC. Tri-layer dielectric system of PMMA/PVA/Al2O3 was used for the fabrication of CuPc based OFETs. PVA layer is polar (contain ?OH groups) and highly sensitive to ambient condition. This layer has been sandwiched between hydrophobic PMMA and anodized Al2O3 layer to protect degradation of PVA layer in ambient. Polarization of ¬?OH groups was found to be highly sensitive to temperature, which was exploited to fabrication of temperature sensors using OFETs. In addition, we have demonstrated remarkable enhancement of OFET performances under ambient condition [1,2]. The observed temperature range is going to be suitable to found application in monitoring body measurement, temperature for chemicals and vaccine, or transporting medicine and organs etc. The devices were also fabricated on flexible substrates and were found to be suitable in flexible applications. References: [1] Enhanced Environmental Stability Induced by Effective Polarization of a Polar Dielectric Layer in a Trilayer Dielectric System of Organic Field-Effect Transistors: A Quantitative Study, Nimmakayala V. V. Subbarao, Murali Gedda, Parameswar K. Iyer and Dipak K. Goswami, ACS Appl. Mater. Interfaces, 7 (2015) 1915?1924 [2] Organic Field-Effect Transistors as High Performance Humidity Sensors with Rapid Response, Recovery Time and Remarkable Ambient Stability, Nimmakayala V. V. Subbarao, Murali Gedda, Parameswar K. Iyer and Dipak K. Goswami, Organic Electronics (2016)

Resume : We investigated the deposition of a silver nanowire (Ag NW) ring generated by being encapsulated inside fine droplets. The regime of the droplet size required to transform the Ag NWs into a ring shape was determined. The electrostatically spray method was used to ensure the generation of fine droplets with a size in the necessary regime for the ring formation. Coiled NW rings were obtained by utilizing the force equilibrium of the NW’s axial stress and the droplet surface tension. When the NW’s axial stress was greater than the pressure change across the droplet surface due to the surface tension, a NW inside a droplet was observed in the form of a coiled ring along the rims of the droplet.

Resume : Recently, the issues of flexible transparent electrode (TE) have attracted a great of attention as the interests in flexible opto-electronics. Indium-tin-oxide is one of the most representative materials as TE, however, its brittleness is a major bottleneck for applying to flexible electronics. For replacement of ITO, many alternative materials such as other metal oxide, graphene and carbon nanotube have been studied. Among the alternatives, a random network of silver nanowires is a viable candidate for replacing ITO because of highly optical transparency, electrical conductivity and mechanical flexibility. Although the great potentials of silver nanowire as TE, unstable thermal and environmental properties of silver nanowire have been prevented commercialization. In this study, we applied plasma technology to silver nanowire TE. Ultrathin film grown on the silver nanowire deposited by plasma process enhance the thermal and environmental stabilities as well as electrical properties without the losses of optical transparency. The hybrid silver nanowire could endure more than 200 Celsius degree of temperature, advance 100% for corrosion resistance compared to pristine silver nanowire transparent electrode. Transparent heater based on the hybrid silver nanowire showed improved lifetime and maximum operation temperature.

Resume : Thick and narrow conductive flexible electrodes were printed on a multilayer coated paper substrate using an electroconductive functional ink, which was designed and formulated for screen-printing. The inks were prepared using simple, non-expensive and eco-friendly materials by blending carbon fibers (CFs) into the matrix of a water-soluble cellulose derivative, such as carboxymethyl cellulose (CMC). For low concentration of CFs (10 wt.%), the printed films exhibit an average resistivity of 4.69 ± 0.95 ?cm , after 10 printing steps and without any post-printing annealing process. After 6 months the ink remained stable and the printed films kept their initial resistance. When bended the resistivity decreases under compressive strain while an abrupt loss on conduction was observed under tensile strain. After 1000 bending cycles, a reduction of the resistivity was observed on the printed films in the flat conditions. The developed ink was successfully used in a fully-screen-printed electric circuit.

Resume : Over the last decade, drop-on-demand inkjet printing has drawn very much interest from printing text or graphics to scientific research [1]. Inkjet printing is precise, quick and inexpensive. Hence it is a good candidate for conductive metallic pattern fabrication. Inks must be manufactured to be suited with the rheological requirements of fluid flow deposited on the proper substrates. Inks are exploited in two different approaches such metallic nanoparticles suspensions, that consist of metal organic precursors in appropriate solvents [2-4] and metal organic decomposition, which is synthesized from metallic salt and formed in “true solution” [5-6]. Herein, we report a study on a simple, economic and low-toxic fabrication route of conductive silver patterns obtained from aqueous ink solutions of silver nitrate (AgNO3) [7]. AgNO3 patterns were printed on flexible polyimide (PI) substrates from 3M of AgNO3 aqueous inks using a DMP 2831 Dimatix-Fujifilm apparatus. To increase the adhesive force between the printed patterns and PI, an extreme small amount of dishwashing detergent of about 0.0025 % (v/v) was added into the ink to act as surfactant, along with oxygen plasma etching treatment. Conductive Ag patterns were achieved via thermal annealing at about 250 °C under argon-5% hydrogen gas flow. We report a systematic analysis of the printed patterns in terms of their morphology and behavior of electrical resistivity as a function of temperature in the 4.2 K to 300 K range.

Resume : Electro photography (laser printing) has emerged to one of the leading print technologies during the last decades. The xerographic process enables the simultaneous two dimensional alignment of multiple toner materials with high spatial resolution (600 dpi, resolution <100 μm). Due to its solvent-free character, a high solid content can be transferred in a single printing cycle, offering the possibility for a quick layer-by-layer construction of three-dimensional objects. [1] However, the conventional melting process prohibits accurate structure building and in contrast to the well-established ink jet process, three-dimensional electro photography has not yet been examined for the assembly of biofunctional materials. Especially the cytotoxicity of common toner components as well as the requirement of high temperatures during the conventional curing procedure have prevented the approach towards this interesting application. Therefore, a new biocompatible class of organic-inorganic composite particles has been developed to be processed as toners at low temperatures using common laser printing techniques. [2] In this paper, we provide a detailed kinetic investigation about the controlled surface functionalization of acrylic particles in respect to the hydrolysis time, temperature and the sodium hydroxide concentration. Furthermore, we have studied the subsequent carbodiimide mediated coupling of numerous functional amines onto the generated carboxylic group.

Resume : In this paper, we summarise our latest research on printed metal oxide transistors on flexible substrates. By using conventional printing processes such as sheet-fed inkjet printing [1] or rotary flexographic printing [2], In-nitrate-based precursor inks can be deposited on substrates and converted via annealing into thin, high-quality In2O3 semiconductor films for thin-film transistor (TFT) applications. The required temperature budget for the precursor to metal-oxide conversion can be reduced from ~300 °C down to 180 °C using far ultraviolet light-assisted (FUV) annealing method [3]. The thickness of the printed semiconductor layer critically affects the TFT device performance, such as the saturation mobility (µsat) and turn-on voltage (Von). The increase in the film thickness leads into a shift in the device operation from enhancement- to depletion-mode which can be exploited in depletion-load NMOS inverters that allow high gains [1]. References: [1] J. Leppäniemi, K. Eiroma, H. S. Majumdar, A. Alastalo, “In2O3 Thin-Film Transistors via Inkjet Printing for Depletion-Load NMOS Inverters”, IEEE Electron Dev. Lett., accepted [2] J. Leppäniemi, O.-H. Huttunen, H. Majumdar, A. Alastalo, “Flexography-Printed In2O3 Semiconductor Layers for High-Mobility Thin-Film Transistors on Flexible Plastic Substrate”, Adv. Mater. 2015, 27, 7168-7175 [3] Appl. Phys. Lett. 2014, 105, 113514

Resume : In the present study, a Resistive Switching Device (RSD) is fabricated by means of inkjet printing. The pristine device shows different switching behaviors according to printed patterns, one being a stable unipolar switching[1] with an on/off ratio of 104. Ageing of RSD is investigated with XPS, which confirmed the oxidation of the silver nanoparticles, leading to a decrease in the “on” state conductivity of the RSD. The second behavior corresponds to a write-once-read-many[2] effect. The present study gives an insight into the field induced formation of conductive silver filament[3], which gives rise to a transition in the resistance. The active switching matrix used in the present case serves as a good ink for an easy deposition onto various substrates thus widening its scope in various fields of printed electronics[4]. 1. Y. Ji, B. Cho, S. Song, M. Choe, T.W. Kim, J.S. Kim, B.S. Choi, T. Lee. Unipolar Bistable Switching of Organic Non-Volatile Memory Devices with Poly(styrene-co-styrenesulfonic acid Na). Journal of Nanoscience and Nanotechnology, 11, 2011, 1385-1388. 2. S. Moller, C. Perlov, W. Jackson, C. Taussig, S.R. Forrest. A polymer /semiconductor write-once-read-many-times memory. Nature, 426, 2003,166-169. 3. E.J Sandouk, J.K. Gimzewski, A.Z. Stieg. Multistate resistive switching in silver nanoparticle films. Sceince and Technology of Advanced Materials, 16(4), 2015. 4. Nanotechnology, Science and Applications, 9, 2015, 1-13.

Resume : The detection of glucose and hydrogen peroxide is a critical analytical goal due to its importance for many fields of science and industry. Despite the fact enzyme sensors are successfully used in clinical practice and produced on industrial scale, they have a number of disadvantages such as high oxygen dependency, low temporal and thermal stability. Alternative to enzyme sensors is the non-enzymatic ones. Researches are shown the promising electrodes have surface with nano-sized feature, because it facilitates the charge transfer and prevents the molecule denaturation. This work presents one-step approach for the fabrication of Cu, Cu-Au and Ni nanostructures electrodes by laser deposition technique. Topology was investigated with the use of a SEM, XRD and EDX. Electrocatalytic activity of sensor platforms towards hydrogen peroxide and glucose was investigated by cyclic voltammetry and amperometry. Cu electrode showed the highest activity, it has a linear dependence of the current-concentration in the range of 10-100 μmol/L for H2O2 and 0.6-3.0 mmol/L for glucose. Research was performed at Educational Resource Center of Chemistry, Center for Geo-Environmental Research and Modeling and Center for X-ray Diffraction Methods of SPSU Research park. Study was funded by RFBR (16-33-00645) and SPSU (12.38.219.2015).