In this study, we experimentally investigated the material flows of coloured dyes in coalescing small inkjet printed droplets of different volume ratios. With two differently coloured dyes, one in each droplet, we were able to distinguish the time-resolved contributions in dye transport across the coalescence bridge due to convection and diffusion. Droplets with differently coloured dyes were inkjet printed onto a glass substrate at a sufficiently large pitch such that they do not touch each other. Under UV exposure, the wetting of the substrate improves, causing the droplets to coalesce. Filmed at 50 fps, the coalescence and mixing of the droplets of volume ratios 1:1, 2:1 and 4:1 was followed. For equally sized drops, the mixing of the dyes shows good agreement with a 1D approximation of Fick’s second law along the central axes of the coalescing droplets with a diffusion coefficient D = 2 9 10-9 m2 s-1. For unequally sized droplets, convective flows from the small to the large droplet were demonstrated. The convective flows increase in size with increasing volume ratio, but only enter the droplet over a small distance. Complete mixing of the dyes in the unequally sized droplets is only reached after a long period and is diffusion controlled. At the initial moment of coalescence of unequally sized droplets, a small convective flow is observed from the large into the small droplets. Further investigation in this phenomenon is recommended.
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Mixing examples of different categories (interleaving) has been shown to promote inductive learning as compared with presenting examples of the same category together (massing). In three studies, we tested whether the advantage of interleaving is exclusively due to the mixing of examples from different categories or to the temporal gap introduced between presentations. In addition, we also tested the role of working memory capacity (WMC). Results showed that the mixing of examples might be the key component that determines improved induction. WMC might also be involved in the interleaving effect: participants with high spans seemed to profit more than participants with low spans from interleaved presentations. Our findings have relevant implications for education. Practice schedules should be individually customised so society as a whole can profit from differences between learners. (PsycINFO Database Record (c) 2017 APA, all rights reserved)
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With a market demand for low cost, easy to produce, flexible and portable applications in healthcare, energy, biomedical or electronics markets, large research programs are initiated to develop new technologies to provide this demand with new innovative ideas. One of these fast developing technologies is organic printed electronics. As the term printed electronics implies, functional materials are printed via, e.g. inkjet, flexo or gravure printing techniques, on to a substrate material. Applications are, among others, organic light emitting diodes (OLED), sensors and Lab-on-a-chip devices. For all these applications, in some way, the interaction of fluids with the substrate is of great importance. The most used substrate materials for these low-cost devices are (coated) paper or plastic. Plastic substrates have a relatively low surface energy which frequently leads to poor wetting and/or poor adhesion of the fluids on the substrates during printing and/ or post-processing. Plasma technology has had a long history in treating materials in order to improve wetting or promote adhesion. The µPlasma patterning tool described in this thesis combines a digital inkjet printing platform with an atmospheric dielectric barrier discharge plasma tool. Thus enabling selective and local plasma treatment, at atmospheric pressure, of substrates without the use of any masking materials. In this thesis, we show that dependent on the gas composition the substrate surface can either be functionalized, thus increasing its surface energy, or material can be deposited on the surface, lowering its surface energy. Through XPS and ATR-FTIR analysis of the treated (polymer) substrate surfaces, chemical modification of the surface structure was confirmed. The chemical modification and wetting properties of the treated substrates remained present for at least one month after storage. Localized changes in wettability through µPlasma patterning were obtained with a resolution of 300µm. Next to the control of wettability of an ink on a substrate in printed electronics is the interaction of ink droplets with themselves of importance. In printing applications, coalescence of droplets is standard practice as consecutive droplets are printed onto, or close to each other. Understanding the behaviour of these droplets upon coalescence is therefore important, especially when the ink droplets are of different composition and/or volume. For droplets of equal volume, it was found that dye transport across the coalescence bridge could be fully described by diffusion only. This is as expected, as due to the droplet symmetry on either side of the bridge, the convective flows towards the bridge are of equal size but opposite in direction. For droplets of unequal volume, the symmetry across the bridge is no longer present. Experimental analysis of these merging droplets show that in the early stages of coalescence a convective flow from the small to large droplet is present. Also, a smaller convective flow of shorter duration from the large into the small droplet was identified. The origin of this flow might be due to the presence of vortices along the interface of the bridge, due to the strong transverse flow to open the bridge. To conclude, three potential applications were showcased. In the first application we used µPlasma patterning to create hydrophilic patterns on hydrophobic dodecyl-trichlorosilane (DTS) covered glass. Capillaries for a Lab-on-a-chip device were successfully created by placing two µPlasma patterned glass slides on top of each other separated by scotch tape. In the second application we showcased the production of a RFID tag via inkjet printing. Functional RFID-tags on paper were created via inkjet printing of silver nanoparticle ink connected to an integrated circuit. The optimal operating frequency of the produced tags is in the range of 860-865 MHz, making them usable for the European market, although the small working range of 1 m needs further improvement. Lastly, we showed the production of a chemresistor based gas sensor. In house synthesised polyemeraldine salt (PANi) was coated by hand on top of inkjet printed silver electrodes. The sensor proved to be equally sensitive to ethanol and water vapour, reducing its selectivity in detecting changes in gas composition.
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Eggshell particles as bio-ceramic in sustainable bioplastic engineering – ESP-BIOPACK Plastics make our lives easier in many ways. However, if they are not properly disposed of, they end up in the environment. Recently, biodegradable biopolymers, such as polylactic acid (PLA) and polyhydroxy alkanoates (PHAs), have moved towards alternatives for applications such as sustainable packaging. The major limitations of these biopolymers are the high cost, which is due to the high cost of the starting materials and the small volumes, and the poor thermal and mechanical properties such as limited processability and low impact resistance. Attempts to modify PHAs have been researched in many ways, such as blending various biodegradable polymers or mixing inorganic mineral fillers. Eggshell (10 million tons per year by 2030) is a natural bio-ceramic mineral with a unique chemical composition of calcium carbonate (>95% calcite). So far it has been regarded as a zero-value waste product, but it could be a great opportunity as raw material to reduce the cost of biopolymers and to improve properties, including the decomposition process at the end-of-life. In this project, we aim to develop eggshell particles that serve as bio-fillers in biopolymers to lower the cost of the product, to improve mechanical properties and to facilitate the validation of end-of-life routes, therefore, economically enhance the wide applications of such. The developed bioplastic packaging materials will be applied in SME partner EGGXPERT’s cosmetics line but also in other packaging applications, such as e.g. biodegradable coffee capsules. To be able to realize the proposed idea, the partnership between Chemelot Innovation and Learning Labs (CHILL), EGGXPERT B.V. and the Research Centre Material Sciences of Zuyd University of Applied Sciences is needed to research the physical, mechanical and end-of-life influences of eggshell particles (ESP) in biopolymers such as PLA and PHA and optimize their performance.
Tijdens het eindevent en in de eindrapportage van het Flow4nano project zijn verschillende onderdelen geïdentificeerd die voor de verdere duurzame doorwerking van de resultaten, en het vergroten van de impact, gewenst zouden zijn. Met deze Top-up willen de verkregen kennis door ontwikkelen en volledige datasets genereren die daarna gepubliceerd kunnen worden om zodoende het onderzoeksveld en bedrijfsleven te informeren over het gecontroleerd maken van nanodeeltjes in flow reactoren. Tevens willen wij door middel van het verwerken van de resultaten in het onderwijscurriculum ook toekomstige generaties studenten inlichten over de mogelijke toepassingen van de in Flow4nano gemaakte materialen. 1. Duurzame doorwerking naar de beroepspraktijk In Flow4nano hebben we twee belangrijke resultaten gehaald die nog niet volledig ingezet kunnen worden in de beroepspraktijk, omdat er nog wat meer onderzoek nodig is en incomplete datasets volledige disseminatie tegenhouden. a) We hebben een flow reactor ontwikkelt die twee vloeistofstromen kan mixen. Om er zeker van te kunnen zijn dat deze reactor ook goed geschikt is voor het maken van nanodeeltjes zijn we begonnen de mixing in deze flow reactor, onder invloed van nanodeeltjes in de vloeistofstromen, in kaart te brengen. De volgende stap hierin is deze dataset compleet te maken en deze te dissemineren naar stakeholders uit de beroepspraktijk via de lectoraatsnieuwsbrief en een poster op het jaarlijkse Nanotechnology crossing borders symposium (organisatoren: TNO/Brightlands Materials Center, Zuyd Hogeschool en Universiteit van Hasselt). b) We hebben kristallijne ZrO2 nanodeeltjes gemaakt. Zo hebben we kunnen aantonen dat onze flow reactoren niet alleen heel precies TiO2 nanodeeltjes kunnen maken, maar bredere inzetbaarheid hebben. Ook hier moeten we de dataset compleet maken en zullen we de resultaten dissemineren naar de beroepspraktijk via de lectoraatsnieuwsbrief en een poster. 2. Duurzame doorwerking naar het onderzoek De resultaten die behaald zullen worden tijdens het in de “duurzame doorwerking naar de beroepspraktijk” paragraaf beschreven onderzoek zijn ook zeer relevant voor het onderzoeksveld. Het is het doel om tijdens het Top-up project deze resultaten te dissemineren in twee open access artikelen, naast de disseminatie naar onderzoeksstakeholders door disseminatie via de lectoraatsnieuwsbrief en de poster. 3. Duurzame doorwerking naar het onderwijs In de laatste maanden van het Flow4nano Pro project is besloten om een nieuw vak aan het programma van de Material Science afstudeerrichting toe te voegen en zodoende het curriculum van de Applied Science studie te verbeteren. Dit vak zal ingaan op de energietoepassingen van materialen (in bijvoorbeeld zonnecellen) en het principe van de optische folies, zoals gemaakt in het Flow4nano project, past hier goed in. Binnen dit Top-up project willen we een set lesmateriaal voor dit vak ontwikkelen.
Granular materials (GMs) are simply a collection of individual particles, e.g., rice, coffee, iron-ore. Although straightforward in appearance, GMs are key to several processes in chemical-pharmaceutical, high-tech, agri-food and energy industry. Examples include laser sintering in additive manufacturing, tableting in pharma or just mixing of your favourite crunchy muesli mix in food industry. However, these bulk material handling processes are notorious for their inefficiency and ineffectiveness. Thereby, affecting the overall expenses and product quality. To understand and enhance the quality of a process, GMs industries utilise computer-simulations, much like how cars and aeroplanes have been designed and optimised since the 1990s. Just as how engineers utilise advanced computer-models to develop our fuel-efficient vehicle design, energy-saving granular processes are also developed utilising physics-based simulation-models, using a computer. Although physics-based models can effectively optimise large-scale processes, creating and simulating a fully representative virtual prototype of a GMs process is very iterative, computationally expensive and time intensive. On the contrary, given the available data, this is where machine learning (ML) could be of immense value. Like how ML has transformed the healthcare, energy and other top sectors, recent ML-based developments for GMs show serious promise in faster virtual prototyping and reduced computational cost. Enabling industries to rapidly design and optimise, enhancing real-time data-driven decision making. GranML aims to empower the GMs industries with ML. We will do so by (i) performing an in-depth GMs-ML literature review, (ii) developing open-access ML implementation guidelines; and (iii) an open-source proof-of-concept for an industry-relevant use case. Eventually, our follow-up mission is to build upon this vital knowledge by (i) expanding the consortium; (ii) co-developing a unified methodology for efficient computer-prototyping, unifying physics- and ML-based technologies for GMs; (iii) enhancing the existing computer-modelling infrastructure; and (iv) validating through industry focused demonstrators.
