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INSPIRED Report Summary

Project ID: 646155
Funded under: H2020-EU.

Periodic Reporting for period 1 - INSPIRED (INdustrial Scale Production of Innovative nanomateRials for printEd Devices)

Reporting period: 2015-01-01 to 2016-06-30

Summary of the context and overall objectives of the project

The INSPIRED project will develop and demonstrate cost-effective, innovative high throughput synthesis and functionalization of nanomaterials already validated in the laboratory (e.g. currently at TRL 4) for printed electronic systems using high volume printing techniques which surpass currently available printing technologies.
This will be achieved through development of high performance, cost effective nanomaterial formulations in a range of commercial applications in relevant industrial environments (TRL6) against the relevant industrial standards and end user applications:
The core of the research activities of the INSPIRED project will be (i) the development of independent synthesis routes for nano-copper, AgNW and graphene (lab scale and then industrial scale quantities for end users), (ii) development and optimisation of the high throughput printing systems and (iii) demonstration of the functional nanomaterials within three exemplar end use systems in relevant industrial environments.
The INSPIRED project consortium consists of specialists in complimentary fields particularly suited towards the development of nanomaterials, ink formulation, printing, and equipment and curing, nanomaterial safety and end use applications of touch screen, LCD displays and thin film photovoltaics (CIGS). The clear objectives of developing and demonstrating in relevant industrial environments the synthesis and functionalization of nanomaterials for printing applications with high throughput will be achieved via well integrated activities during 11 work packages. Throughout the project we will consider safe-by-design approaches and will conduct nanosafety assessments at each step of the production process (from BioNanoNet) in partnership with nanomaterials producers (IML, Nanogap, SWAN), equipment and process developers (NTCW and M-Solv) and end users (TNx, Nexcis/Midsummer and EuroLCDs) with technology support from the Universities of Bologna and Santiago de Compostela Dissemination activities will be led by NIA.

The key exemplar technologies to be demonstrated include:

Capacitive touch screen - Capacitive touch panels (CTS) are used, rather than resistive touch panels, in almost all smartphones and tablets. They offer greatly improved sensitivity and multi-touch capability. Current devices are generally based on double sided (x and y position location) designs on ~0.5 mm thick glass or on pairs of PET foils laminated together. Bus bars are generally required at the panel edges to connect the electrodes to the cable connector made from screen printed silver. There is a strong industry pull towards developing better performing, lighter devices which are less expensive and towards all-digital processing to allow lower volume projects to be realised.
INSPIRED will develop nano-copper ink formulations which can be inkjet printed and laser patterned to form the copper bus bars to replace the screen printed silver currently used. Additionally, ITO will be replaced with Ag nanowires in combination to enable new large area CTS.

LCD display signage - Over the past decade, display technologies have seen major advances in resolution and drastic cost reductions. Researchers are now pushing the limits to further reduce costs and increase performance (switching speed, contrast and increased readability characteristics, information safety), quality of experience and energy efficiency.
We will be developing optically transparent conductive materials to replace ITO which could be used to drive high capacitance liquid crystal displays as conventionally used ITO has relatively high electrical resistance, to further reduce costs and increase performance to reduce switching speed and energy consumption.

Solar cell – Nexcis (latterly Midsummer) focus on the development of thin film CIGs modules using electrodeposition techniques which are able to accurately control the thickness of Cu, In and Ga layers with a high thickness uniformity ≤3% (eq. PVD). The process has uses Ag based metal grid for cell interconnect (independent of ZnO resistivity) and has easy tuning of I/V modules characteristics.
The project aims to replace the Ag grid with nano-copper as a cost reduction measure and to use inkjet printing as opposed to the conventionally used screen printing process. Therefore INSPIRED will develop nano-copper ink formulations and the corresponding inkjet printing process to deposit interconnects and will also develop silver nanowires which can be deposited using printing technologies in order to replace the standard TCO material.

Nanosafety – The INSPIRED consortium are duly committed to assessing risks associated with nanomaterials. Therefore, future development of nanomaterials and nanomaterials formulations will consider exposure assessment, both via experimental activity and modelling, for groups of products, activities, and uses. We will build upon the outputs from the NanoREG and NanoFORCE projects through involvement of BioNanoNet .

The successful outcome of the INSPIRED project will have a significant impact on the promotion of strategic targets of the European economy and society as described in the call for proposals. The technologies developed will extend the limits of conventional printed electronics solutions by providing cost effective solution to the synthesis and functionalization of nanomaterials for printing applications with high process throughput. Successful application and commercialisation for the INSPIRED technology will:
• Create new market opportunities for SME nanomaterial suppliers (IML, Nanogap and Swan);
• Promote closer collaboration between supply chain partners (nanomaterials suppliers, printing process equipment manufacturers and developers (M-Solv) and end users (TNx, Nexcis and EuroLCDs) thus leading to competitive advantage;
• Contribute to standardisation of nanomaterials and high volume printing process to enable better product and process design (NTCW, M-Solv and IML) enhanced through material characterisation (TEC) and process simulation expertise (UNIBO)
• Promote safe-by-design principals through collaboration with EU nanosafety cluster through inclusion in the consortium of key players in this network (BNN and NIA).

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The work is centred around the production of three different types of nanoparticles – nano-copper, silver nanowires and graphene nonoplatelets. The three types of particles are then formulated into inks which are used to fabricate printed electronic structures. This involves the printing and coating of the nanoparticle inks, further processing steps and then using them in various applications.

The first stage was to set the target parameters and specifications for the particle production and ink formulation. This was based on requirements for the end users, but taking into account the practicalities of particle synthesis and processing.

The approach to copper nanoparticle production is through the use of a high power plasma torch. The processes occurring in the plasma, and the condensation of particles are extremely complex, so advanced modelling work was carried out to understand the processes occurring in the plasma and the production rig. This has enabled parameters and configurations to be identified which optimise the particle manufacture. A review of the production has also identified methods to make the particle production more cost effective. Copper nanoparticles have been formulated into a number of different inks with different properties for different printing methods and applications. Key formulations have been created for digital ink-jet printing, with low viscosities and control over stability and surface tension. High viscosity copper pastes have been produced for screen printing, which can be used to produce thicker copper lines for a high degree of electrical conduction.

Silver nanowires offer the potential to make transparent coatings with high electrical conductivity. Work in this project has been focussed on understanding the parameters involved in the synthesis of these fibres, and in optimising a production procedure to increase the production from laboratory synthesis to a pilot scale. By improving the conditions, the production yield of the standard grade silver nanowires was almost doubled. The reproducibility of the nanowires produced has also been improved. On the laboratory scale further tuning of the reaction conditions and materials has enabled fibres to be made with a range of different properties. In particular interest is a thinner variety of silver nanowires with particularly good transparency, which is planned to be the next target for scale-up. Work is also being carried out to formulate these materials into inks and sprayable coatings.

The objective for the graphene work is to develop and optimize a large scale exfoliation process for the production of nanoplatelet materials. The primary focus is the scaling up of the manufacturing capability of SWAN`s Elicarb® Graphene Grades, to a scale sufficient to support the needs of the flexible electronics industry, from a starting point of a few grams per day up to approximately 25 kg/day quantities. Optimization of the process has involved maximizing recovery of “waste” materials back into the process along with optimizing the first pass yield of graphene nanoplatelets. Other modifications to the graphene production have enabled the process to become more efficient, reducing operating costs and reducing process waste. Root cause analysis techniques were used to overcome problems with the wear of a particular component and statistical process control has been used to determine the consistency of manufacture according to quality control procedures. Three different grades of graphene platelets have been produced with different particle sizes. These have been dispersed into various solvents, with the best stability found in a water/alcohol blend. These dispersions form the basis of graphene inks which could also be combined with silver nanowires.

Ink-jet printing of copper tracks using nano-particle inks has been successful with controlled fine lines being produced. This required some feedback and formulation changes to control the wetting and spreading of the ink which depended on the particular substrate. Ink-jet printing with silver nanowires did not work so well due to Ink-jet system limitations, but films were successfully deposited using spray deposition.

The copper ink is not conductive as-printed, due to surface oxidation of the copper particles, but requires an extra sintering step to give high conductivity tracks. There are a number of ways to do this. In this project an advanced laser treatment has been used. This not only gave good conductivity and adhesion but the equipment has been developed to track the copper lines so that all the laser power is focused on the ink ensuring maximum effect and preventing any possible laser damage to the surrounding material. Laser equipment has also been used to create fine line patterns, both in nano-copper ink and in silver nanowire coatings.

A variety of characterization techniques have been used to investigate the properties of the nano-particles, inks and substrates. These include atomic force microscopy (AFM), dynamic light scattering, zeta potential measurement, contact angle analysis, surface tension measurement, rheometry, fluorescence spectroscopy, mass spectrometry (ESI-MS, MALDI-TOF-MS), atomic spectroscopy (FAAS, ETAAS, ICP), scanning and transmission electron microscopies (SEM, TEM) and thermogravimetry (TGA). These have all helped in understanding the materials and their interactions which in turn feeds back into the optimisation of the process.

A survey has been carried out to understand the market for touchscreen devices and the potential for using nanoparticle inks. One particular potential identified was the possible use of silver nanowire transparent conductive layers in flexible devices, as they are less brittle than the normal ITO coatings. A test prototype touchscreen device was produced using ink-jet printed lines copper ink, although further work is required to make this fully functioning.

Spray deposited silver nanowires have been assessed in for LCD applications. Commercially available silver nanowires did not have sufficient transparency, but initial indications are that the nanowires being produced in this project will be much better in this respect. Protective coatings are being investigated for enhancing the durability. Copper busbars have also been deposited as an initial investigation. The conductivity of the lines was encouraging, but further work is required to improve the adhesion to the substrate. Additionally protective coatings were investigated for the copper patterns.

For CIGS solar cells, copper nanoparticle printed inks have been assessed with the aim of being able to replace the more expensive existing silver inks. Screen printed copper lines have shown good adhesion to the surface of the cells and good conductivity when laser sintered. The original work was carried out on the Nexcis cells but with their leaving the project this is now being repeated on Midsummer CIGS cells with similarly encouraging results so far. There is a possible contamination issue which may arise from the sintering of the paste which still needs to be resolved.

An important part of the scaling up of the project is the assessment of health and safety of the materials and processes involved. Preliminary assessments have already been carried out and protocols established for a more thorough risk analysis when the production methods and materials are more established. This will lead to guidelines for the safe use and production of the nanomaterials.

Thirty five dissemination activities have been conducted to date, including conferences presentations and posters, newsletters, trade exhibitions and publications. Three patent applications have been filed, and a website has been created for the project. Twelve exploitable results were identified within the scope of the project.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Some of the main points of progress beyond the state of the art are as follows:

An advanced exfoliation method for producing graphene had been developed at the beginning of this project. This project has progressed this beyond the existing state of the art by scaling from being able to produce a few grams in the laboratory to a more industrially relevant, commercial scale which will be able to produce large quantities, consistent with achieving a TRL of 6 and above. In order to achieve this, improved methods for separation and purification have been developed, as well as novel methods for improving the yield of the graphene.

An advanced model has been developed which has enabled greater insight than before into the complex processes occurring in plasma based nanoparticle synthesis. This has been applied to the parameters for manufacturing copper nanoparticles enabling greater insight into the important factors for process optimisation - in particular the effect of radiative cooling on the evaporation efficiency and the effect of using passive versus active quenching with the cooling gas.

New nanoparticle copper based inks have been developed with a greater control of stability, surface tension and viscosity. This has enabled improved ink-jet performance in combination with optimised printer settings.

The laser sintering of printed copper inks to produce high conductivity tracks has been improved beyond previously achievable results. New optical designs have been used to demonstrate high speed sintering, with tracking of the laser directly onto the printed metal lines. This means that the sintering is faster, more precise and of higher quality.

The first demonstration of working copper interconnects for CIGS solar cells has been made. Previously this had only been achieved using expensive silver paste.
The copper tracks were formed on the CIGS cells by screen printing a specially formulated copper paste, together with precisely targeted laser sintering.

The technology for the production of 20 nm nanowires synthesised in this project is still state of the art, in comparison to the thinnest commercially available nanowires at 30 nm. The narrow diameter of these wires is expected to lead to even further improvements in optical transparency. In the first 18 months of this project, methods for producing these 20 nm nanowires have improved although further work is required on scale-up and purification methods before a product could be made commercially available.

The first ever demonstration of working silver nanowire touch sensor has been formed by spray coating and laser pattering.

The above developments beyond the state of the art have led to three patent applications and two scientific publications to date, as well as a number of conference presentations and posters.

The immediate impact will be on the advancement of the production of the nanomaterials, manufacture and performance of inks for printed electronics as well as the equipment for printing and processing these materials, and the advancement of their potential uses in touchscreens, displays and CIGS solar cells. In the longer term the project will have a direct positive impact across the entire printed electronics sector value chain, benefiting the nanomaterial suppliers, ink manufacturers, printing companies and equipment suppliers and the high value manufacturing sectors. Each of these partners are already very active in the use of nanomaterial formulations, printing equipment, electronics and printed electronics in their particular sectors which are all of high strategic importance to the EU economy and will all benefit from increased uptake of printed production high value multi-functional electronic structures and components. The INSPIRED project is an industry-driven Research and Innovation Action that supports the objectives and vision of the “Nanotechnologies, Advanced Materials and Production” programme by increasing the technology base of these EU manufacturers, enabling them to adapt to global competitive pressures. INSPIRED will contribute to each of the Europe 2020 targets, through: (i) Increased employment of 20-64 year-olds; (ii) Increased R&D spending; (iii) Reduced energy usage and greenhouse gas emissions and (iv) Increased education, especially at third level education.

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