The authors would like to acknowledge Innovate UK for funding this research under the DIRECT (33417-239227) and PCAP (27508-196153) projects. The authors would also like to thank PVOH Polymers Ltd., for providing materials and professional guidance during this work, and Unilever, AkzoNobel, and Carclo Technical Plastics, for their support.

1. Ink Formulation
<ol>
	<li>Prepare the solution for IJP by dissolving polyvinyl alcohol (8 wt.% PVOH in water) in purified water heated to 60 &#176;C.</li>
	<li>Add 10 g of mono-propylene glycol (MPG) (10 wt.% mono-propylene glycol in water), as a humectant, to the solution. 
	NOTE: The role of the humectant is to prevent blockages in the printhead.</li>
	<li>Stir the solution for several hours to ensure homogeneity and then filter it through a 5 &#181;m filter to remove any particulates that might block the noz...

<ol>
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M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inkjet+printing+-+the+physics+of+manipulating+liquid+jets+and+drops.">Inkjet printing - the physics of manipulating liquid jets and drops.</a> J Phys Conf Series. 105, 012001 (2008).</li><li>Derby, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inkjet+printing+of+functional+and+structural+materials:+Fluid+properties+requirements,+feature+stability+and+resolution.">Inkjet printing of functional and structural materials: Fluid properties requirements, feature stability and resolution.</a> Annu. Rev. Mater. Res. 40, 395-414 (2010).</li><li>Salaoru, I., Zhou, Z., Morris, P., Gibbons, G. 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In this work, we successfully demonstrated the ability of inkjet printing technology to deposit polymer multilayers. The rheological behavior was investigated, and the experimental results demonstrate that the formulated ink displays pseudoplastic shear thinning behavior. Also, the PVOH ink is a neutral solution (pH 7) and shows good stability over time. Notably, it was successfully demonstrated that IJP technology is capable of producing polyvinyl alcohol multilayer structures, but further improvements in printing cover...

Polyvinyl alcohol is semicrystalline, artificial, non-toxic, water-soluble, insoluble in most organic solvents, biodegradable, and biocompatible in human tissues and has excellent gas-barrier properties1. Furthermore, due to its many useful properties, PVOH is widely used in a large number of applications. Nowadays, PVOH is used in: the manufacture of cleaning and detergent products, the food packaging industry, water treatment, textile, agriculture, and construction (as additives)1. However, PVOH has recently attracted an increased amount of attention for pharmaceutical uses2 (i.e., drug delivery) and in medical applications3,4 (e.g., wound dressing, soft contact lenses, eye drops, and soft implants for cartilage replacement). PVOH films are produced either through a melt or solution form. Melt processing is compatible only with PVOH with low hydrolysis levels or heavily plasticized PVOH. Thus, when using this pathway, some properties can be sacrificed1. On the other hand, a PVOH layer can be deposited via the solution form by drop casting5, spin coating6, or electrospinning7. However, these methods have a number of limitations in terms of the waste of unwanted material. For example, in the case of spin coating, it has been reported8 that 95% of the material is wasted. Additionally, these methods are quite rigid in term of design/features (no patterning capability) and have high overall processing costs. In order to overcome the limitation of the conventional solution processing, we here explore the potential of inkjet printing technology to provide a novel platform to produce polyvinyl alcohol (PVOH) multi-layer structures that have a strong impact on both the material and application perspectives.
Recent developments in the manufacturing sector have focused on cheap, simple, eco-friendly, and energy-saving processes. Inkjet printing (IJP) is a modern fabrication process that fits perfectly within this framework. The major advantages of IJP technology are the efficiency of material use, the digital (mask-free) and additive patterning, the large area capability, the compatibility with rigid/flexible substrates, and the low cost.
IJP is a deposition method that uses polymeric materials dispersed in a solvent. To date, functional polymer-9, ceramic-10, conductive nanomaterial-11, 2D-12, biologically-, and pharmaceutically-based13 materials have been successfully deposited. Recently, it has been reported that IJP was involved in the deposition of components as part of electronic devices, such as transistors14, sensors15, solar cells16, and memory devices17, as well in electronic packaging18.
The ink, cartridge, and substrate are equally important components that are employed in the printing process. First, the physical properties of the ink, such as the surface tension and the rheological properties (i.e., shear viscosity), have a significant impact on the printability behavior. Also, the pH plays an important role on both the solution (e.g., drying, foaming, and viscosity) and on the lifetime of the IJP print cartridge. Second, for the cartridge (piezoelectric), the driving voltage waveform actually defines the drop formation and both the directionality and the uniformity of the liquid jet. Finally, it is imperative that the ink/substrate interaction is very well understood, as the resolution and accuracy of the printed object are strongly dependent upon this interface. Solvent evaporation, phase changes from liquid to solid, and chemical reactions are the main processes that occur between the fluid drop and the substrate. All aspects involved in the IJP, from ink properties to drop/substrate mechanisms, are highlighted in review papers by Hutchings19 and by Derby20.
In this study, we explore the capabilities of IJP to manufacture polyvinyl alcohol multilayers. First, a PVOH water-based ink was formulated, and the main physical properties, such as rheological behavior, surface tension, and pH, were investigated. In this work, a piezoelectric inkjet printer was employed, and the appropriate waveform parameters were then identified. PVOH multilayers were printed, and the quality and surface/thickness profiles were assessed by optical microscopy.

<table border="0" cellpadding="0" cellspacing="0" width="573">
	<tbody>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Polyvinyl alcohol&#160;</td>
			<td style="width:71px;">PVOH Polymers Ltd, UK</td>
			<td style="width:119px;">Poval 4-88</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;">Mono-propylene glycol&#160;</td>
			<td style="width:71px;">Sigma Aldrich, UK</td>
			<td style="width:119px;">W29004</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">DV2T viscometer&#160;</td>
			<td style="width:71px;">Brookfield, UK</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Attension Theta Optical Tensiometer&#160;</td>
			<td style="width:71px;">Biolin Scientific, Sweden</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">HANNA pH meter&#160;</td>
			<td style="width:71px;">HANNA Instruments, UK</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">industrial Inkjet XYPrint100Z</td>
			<td style="width:71px;">Industrial Inkjet Ltd, UK</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">ContourGT-K 3D optical microscope&#160;</td>
			<td style="width:71px;">Bruker Corp, USA</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

inkjet-printed polyvinyl alcohol multilayers

Inkjet printing is a modern method for polymer processing, and in this work, we demonstrate that this technology is capable of producing polyvinyl alcohol (PVOH) multilayer structures. A polyvinyl alcohol aqueous solution was formulated. The intrinsic properties of the ink, such as surface tension, viscosity, pH, and time stability, were investigated. The PVOH-based ink was a neutral solution (pH 6.7) with a surface tension of 39.3 mN/m and a viscosity of 7.5 cP. The ink displayed pseudoplastic (non-Newtonian shear thinning) behavior at low shear rates, and overall, it demonstrated good time stability. The wettability of the ink on different substrates was investigated, and glass was identified as the most suitable substrate in this particular case. A proprietary 3D inkjet printer was employed to manufacture polymer multilayer structures. The morphology, surface profile, and thickness uniformity of inkjet-printed multilayers were evaluated via optical microscopy.

The physical properties of PVOH water-based ink, such as surface tension, viscosity/rheological behavior, pH, wetting, and time stability, were investigated. The viscosity of the ink used in this work was 7.5 cP, and the surface tension was 39.3 mN/m. Additionally, the formulated ink was neutral (pH 7), with the results summarized in Table 1.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Ink</...

Watch this Scientific Journal Video about Inkjet-printed Polyvinyl Alcohol Multilayers at JoVE.com

Inkjet-printed Polyvinyl Alcohol Multilayers

An inkjet printer was used to manufacture polyvinyl alcohol multilayers. Polyvinyl alcohol water-based ink was formulated, and the main physical properties were investigated.

Inkjet printing is a modern method for polymer processing, and in this work, we demonstrate that this technology is capable of producing polyvinyl alcohol ...

The overall goal of this procedure is to manufacture polyvinyl alcohol multilayers using inkjet printing methods. Inkjet printing is a flexible and efficient, free printing technology that enables us to manufacture complex 3D structures in multiple materials. The main advantages of this technique are the efficiency in material use, digital and additive partnering, noncontact process, compatibility with many materials in substrate, room temperature deposition, high speed and low cost fabrication.To begin this procedure, heat a beaker of purified water to 60 degrees Celsius. Add polyvinyl alcohol such that the final weight percentage of polyvinyl alcohol in solution is 8%Then add monopropylene glycol such that its final weight percentage in solution is 10%Stir the solution for six to eight hours to ensure homogeneity. After this, filter the solution through a five micrometer filter.Visually assess the ink for homogeneity and signs of sedimentation. Characterize the ink as outlined in the text protocol. Next, thoroughly clean the glass substrate, first with acetone and then with deionized water.Using a nitrogen spray gun, dry the wash substrate. Load the substrate onto the print bed and secure it firmly. Flush ink through the print head to remove any air or cleaning solution from the reservoir and nozzles.After this, load the cartridge into the printer. Connect the print head to the GIS print manager via the head personality board. Load the ink solution into the 150 milliliter syringe situated above the cartridge.Seal the syringe with an air tight cap. Next, press the purge button to purge the ink through the nozzle. After setting up the wave form and printing parameters, load the desired image for printing.Start the digital process and print the image pattern onto the substrate. Then, analyze the printed pattern as outlined in the text protocol. In this study, the physical properties of PVOH water based ink are investigated.The reological behavior is examined by measuring the viscosity as a function of shear rate. The viscosity is seen to decrease with increasing shear rate, which suggests the ink displays pseudoplastic shear thinning behavior. The ink's stability is then tested by measuring the viscosity and pH as a function of time over 30 days.The average viscosity is 7.76 centipoys while the average pH is 6.71, which reveals that the ink is very stable over time. The wetting behavior of the ink is then investigated. As can be seen, the PVOH ink demonstrates a good level of wettability with the first contact contact angle of 54.5 degrees.A slight decrease in the contact angle is then observed for the first 25 seconds after which it stabilizes. An optical micrograph of the inkjet printing with 10 layers of printing passes shows a number of defects generated by the ring coffee stain effect. However, the quality is seen to improve significantly with 75 layers of printing passes.This may be the result of a shift in solvent evaporation rate and the change in interface interaction between the additional overlapping layers. After watching this video, you should have a good understanding of how to formulate an ink and about all steps required to paint the pot in using an additive layer manufacturing method called ink jet printing. Overall, our goal was to explore the potential of ink jet printing technology to provide another platform for producing polyvinyl alcohol multilayers.The interest for many industry sectors has gained momentum for this technology. We now have the ability to dose actives in a precise multilayer structure while protecting the consumer or the active with a soluble protective eight of barrier layer.

inkjet-printed-polyvinyl-alcohol-multilayers

Research

JoVE Journal

Engineering

12.5K vistas.  De Montfort University. The overall goal of this procedure is to manufacture polyvinyl alcohol multilayers using inkjet printing methods. Inkjet printing is a flexible and efficient, free printing technology that enables us to manufacture complex 3D structures in multiple materials. The main advantages of this technique are the efficiency in material use, digital and additive partnering, noncontact process, compatibility with many materials in substrate, room temperature deposition, high speed and low cost fabricati...