Technical validation and feasibility of combined planarising and insulating intermediate layers for BIPVs
Keywords: Building Integrated Photovoltaics, printing, coating, steel substrates, intermediate layer
The versatility of printing technologies and their intrinsic ability to outperform other techniques in large-area deposition gives scope to revolutionize the building integrated photovoltaic (BIPV) manufacturing field. Printing allows the delivery of PVs with low fabrication cost per unit area and is also highly compatible with large area steel substrates. Among the third generation PVs the thin-film solar cells (TFSC) such as amorphous silicon (a-Si:H) show great potential for BIPVs. To accelerate their commercialization in BIPVs large-area functionalised steel substrates are needed.
The technical feasibility of steel/intermediate layer (IL) solutions was shown through different prototypes such as 30cm x 30cm sheets and 30cm wide coils. In this study functionalised steels were fabricated by large scale screen printing in ambient environment (humility ∼50%, temperature ∼20 °C), which produced steel/intermediate layer lengths as long as 30 cm and 250 m. A functional layer such as solvent resistant dielectric was successfully used to fabricate 30cm x 30cm demonstrators on four “rough” steel substrates and showed good performance with an amorphous silicon (a-Si:H) TFSC. Results of extensive characterisation of ILs printed onto four steel substrates, such as AISI430 stainless steel, DCO1 bare cold rolled low carbon steel as well as DX51D hot-dip galvanized with Zn (DX51D + Z) or Al (DX51D + AS) which was cold rolled to achieve the desired final thickness, are reported. Ra and Rz surface roughness parameters used in the statistical process control and process capability study are discussed in more detail.
Two different functional layers such as commercially available dielectrics were used to fabricate 250m long demonstrators on AISI430 stainless steel substrate. We have highlighted critical challenges in achieving smooth insulating IL on the stainless steel coil.
This study provides low-cost, large-scale techniques to fabricate large-area functionalised steels with great potential applications in BIPVs.
The Application of smart packaging in the food industry for spoilage detection and extended shelf life in high value food products.
This project aims to offer a solution to replace expiry dates on food packaging with a more accurate detection system, broadly termed, smart packaging.
A small ultra-low cost antenna will be printed onto food packaging and can be scanned to communicate the freshness of a food product to an operating system, controlled by the customer or industrial process. Additionally, the sensor will minimise food waste by providing real-time feedback on the food state rather than assumptions made by the manufacturers and customers. This will aid in the reduction of the 1.3 billion tonnes of food that is lost or wasted each year, which equates to approximately one third of all food production according to the Food and Agricultural Organisation of the United Nations.
This research will offer the food industry a valuable platform from which products can be tracked and freshness monitored throughout the manufacturing process and distribution lines, increasing visibility and enabling data analysis to improve efficiency. This cheap alternative to Amazon’s automated checkout system will reduce company losses via stolen goods and speed up customer check out times. This project offers benefits to both company and customer, and will be adaptable to easily work with other technologies in the bio-detection field.
Development and evaluation of low-cost solutions for urban air quality management
Globally, Cities are growing at an unprecedented pace, putting pressure on space, existing infrastructure and resources. Designing and planning sustainable cities, resilient to environmental and population change, which also promote human wellbeing and healthy lifestyles, is therefor one of the greatest challenges of the 21st century. Air pollution remains one of the biggest threats to human health and wellbeing and is also an increasing economic strain across all sectors of modern day living. Effective urban planning therefore requires a clear understanding of the interactions between the social, economic, and physical process operating in these cities with the management of air quality requiring the same modern solutions that are being applied to other domains within the urban environment.
The effect of screen printing parameters on print quality
Screen Printing is a very versatile and popular process, currently responsible for producing around 98% of printed electronics. An improved understanding of the science behind optimising parameters for functional inks would be beneficial to a range of applications. Some of which could include photovoltaics, for improving the performance of the carbon electrode in perovskite solar cells. As well as carbon-based electrodes in a variety of biosensors.
Studies have been conducted to assess the effect of a range of screen printing parameters, such as snap off distance, squeegee angle and print speed, in terms of their effects on print performance characteristics such as print resolution, roughness and conductivity. Additionally, the microstructures of the printed functional materials are explored to assess the links between particle orientation, alignment and distribution with print performance.
Control of flexographic print properties through tailored ink rheology
Keywords: flexography, non-uniformity, rheology, extensional flow
With the advent of printable electronics, new challenges have arisen that must be overcome to realise the full potential of functional printing. Among these challenges is print non-uniformity, which typically occurs in roller processes as a result of surface instabilities. This work seeks to understand the effects of ink rheology on flexographic print uniformity, paying particular attention to extensional flows. As such it is shown that specific print properties, both functional and graphical, may be obtained through tailored ink rheology.
This research was supported by EPSRC (EP/M008827/1)
The effects of plasma functionalization on the print performance and time stability of graphene-nanoplatelet inks.
Graphene nano-platelets are high aspect ratio nano-particles which due to carbon’s inert nature and their high specific surface area tend to agglomerate under Brownian motion due to van der Waals forces. Plasma functionalisation is a surface treatment method that involves bombarding the surface of nano-particles with a high energy plasma gas within a vacuum, removing any contamination that may be present and replacing them with specific functional groups. This paper examines how NH3 plasma functionalisation affects the print and electronic performance of graphene nano-platelet inks at different concentrations and how we can identify the dispersion and subsequent agglomeration of these nano-particles by studying their complex rheology in time.
Hybrid coatings based on nanocellulose/silver nanowires to develop barrier and antimicrobial properties for active packaging applications
Hugo Spieser1, Aurore Denneulin1, Davide Deganello2, David Gethin2, Julien Bras1, 3
Keywords: Cellulose nanofibrils, silver nanowires, antimicrobial properties, barrier properties, packaging
The field of nanocellulose science has met a strong enthusiasm in the past ten years. Especially due to their exceptional properties (mechanical properties, film forming, rheological modifier, barrier properties, etc.), cellulose nanofibrils (CNF) can have numerous applications such as printed electronics, cosmetics, tissue engineering, or packaging, etc. Today, packaging is expected to fulfill more and more requirements such as being light, strong, recyclable, biodegradable, etc. More recently the potential for the integration of advanced functionalities such as sensing, active functions and security is being explored. For instance, silver nanoparticles have been deeply studied for their antimicrobial activity in polymer nanocomposites and the packaging field remains still a challenge.
Within this framework, this work proposes to explore the barrier and antimicrobial properties of hybrid systems based on the combination of cellulose nanofibrils and silver nanowires (Ag NWs). Hybrid layers of CNF/Ag NWs systems were deposited on PET and PLA polymer substrates using bar coater process. The morphology of the coated layers was found to be well structured and the resulting barrier properties of the films were increased. The coated films also display a strong antibacterial effect and the thickness of the layers was optimized compared to antimicrobial efficiency. A relative high transparency was then achieved for a 100% antibacterial activity against E. coli. Finally, due to the strong entanglement of the cellulose nanofibrils network and the interaction with the active silver nanowires, the activity of the designed materials was found to be working by contact only, making it very promising for the targeted food packaging application.
Using advanced rheology to link mechanical properties of model screen inks with print outcome
“The printing industry often relies on crude measures of rheology which frequently bear no correlation with print quality. This is unsurprising since the techniques employed (e.g. flow cups, tack testers) lack relevance to the print process (in which the material is exposed to a complex fluid dynamical environment) or the complex rheological nature of the process fluids (which are usually non-Newtonian and frequently viscoelastic). This work makes a major advance in quality assurance in establishing that there is a relationship between print quality parameters and rheological data obtained using the advanced rheometric technique of Controlled Stress Parallel Superposition (CSPS). The benefit of using a novel multifrequency implementation of CSPS, known as Fourier Transform CSPS (FT-CSPS) in reducing the time required to characterise each sample is also demonstrated. The development of FT-CSPS has the potential to provide the basis for in line, real time, measurement and control of ink rheology in applications associated with formulation and processing of functional inks and coatings.”
Testing of flexible printed wires for wearable technology
One of the major issues affecting wearable technology is how do you connect all the sensors, control board, power supply and outputs together. The problem with conventional wiring is that it can be bulky and time consuming to attach. Using printed wires which can be pressed or printed directly onto the fabric would significantly improve the performance, look and feel of the final garment. The printed wires would need to be flexible, conductive and insulted.
This talk covers the testing procedure for analysing the performance of flexible printed wires, including variations in the ink formulation and substrate. The prints were made using conductive silver and carbon inks on the DEK 248 screen press to produce samples suitable for stretch testing using the houndsfield. The samples were pulled at different strain rates and the change in electrical properties and the force required to produce the strain were recorded, allowing the best combination of formulation and substrate to be determined.
Formulation of NASICON as a solid electrolyte for a sea water open cathode battery’
NASICON is a ceramic material adopted as a solid electrolyte for sodium batteries. NASICON has a relatively high inherent ionic conductivity but performs poorly in comparison to liquid electrolytes. This work presents an investigation into the effect of particle size and processing conditions on the electrochemical performance of NASICON, with an emphasis on performance in the sea-water cell. Alongside, consideration is given to manufacturing optimisation, which is of major importance to the future adoption of NASICON type materials.