An investigation of inkjet printing of polycaprolactone based inks

Traditional manufacturing methods like moulding or subtractive manufacturing place significant limitations on structures which could be manufactured in a single process. These limitations can now be overcome by a new manufacturing technology—Additive Manufacturing (AM), which provides the users much more freedom to design and produce structures in one piece. Additive manufacturing refers to a range of processing technologies, which fabricate 3D parts by adding successive layers. With this technology, complex 3D structures can be produced directly following the production of a geometric data. Additive manufacturing also enables production without the need of tooling, which brings the prospect of a revolution in the manufacturing industry. Material jetting is one of the additive manufacturing techniques, which generates material layers through inkjet printing. This technology also allows the user to build structures consisting of more than one material, which further expands the capability of additive manufacturing to include the production of multi-functional products. However, due to the strict requirements on the rheology of usable inks, there is a limited number of materials available for use in this technology. This research aims to develop a novel polycaprolactone based ink which is suitable for material jetting and could be potentially used for fabricating scaffolds. The bespoke nature of these devices often require a complex structures, customized design and small batch sizes, which all together make the product costly when using the traditional manufacturing methods. Additive manufacturing technology can reduce these costs, in the main due to the nil marginal cost (e.g. tooling cost, mould design etc.) when changing product design. In addition, material jetting can also incorporate multi-materials or multi-functional devices, mixing several materials at micron level, potentially enabling more advanced and intelligent functions to be incorporated into the final devices. In this project, Polycaprolactone (PCL), commonly used for its biodegradable properties, was investigated as a candidate for material jetting. Both solvent based and UV reaction based jetting techniques were attempted to build up an understanding of the aspects and parameters involved in material jetting ink development and jetting parameter optimization. For solvent based PCL ink, PCL flakes were dissolved into various solvents with different concentrations to prepare a low viscosity ink which could be printed. Volatility, viscosity and surface tension were investigated to confirm that the prepared ink was suitable for jetting. PCL with 5wt% in 1,4-dioxane was successfully jetted by using a Dimatix material printer. A range of experiments were carried out to investigate the ink’s printability under different conditions. During the study, efficiency limitation for solvent based ink was also realized. In order to meet the printing viscosity limit of the inkjet printheads, the loading level of a solute in a solvent ink as well as the efficiency of stacking precipitated layers were both restricted. This curbed the possibility of solvent based ink be applied in making large 3D parts. For UV reaction based inks, the printed ink can fully solidify to form structures after UV illumination, which overcame the processing efficiency limitation of the initial solvent based inks. Pure PCL is not UV curable and therefore chemical modifications were made to graft UV curable functional groups into the PCL structure. The rheology of synthesized UV curable PCL polymers were studied and modified to make them suitable for material jetting. Different photoinitiators were also investigated to work out the suitable composition to achieve real-time curing. Oxygen inhibition was found to be the main side effect which inhibited the curing reaction in an air environment. Type II photoinitiators can help overcome this effect and 3D structures were able to be obtained in both air and nitrogen. It was also found that a nitrogen environment can improve the properties of the printed specimens and the printed samples showed better hardness and modulus than those in printed in air. It was also noted that the increasing concentration of the photoinitiator can improve the curing speed of the ink printed in air. However the samples with higher concentration of photoinitiators manifested a reduction of hardness and modulus. A post-curing procedure, carried out using further UV illumination, was shown to help improve both the hardness and the modulus, but this improvement was limited to the directly illuminated surface

Design of highly stabilized nanocomposite inks based on biodegradable polymer-matrix and gold nanoparticles for Inkjet Printing

Nowadays there is a worldwide growing interest in the Inkjet Printing technology owing to its potentially high levels of geometrical complexity, personalization and resolution. There is also social concern about usage, disposal and accumulation of plastic materials. In this work, it is shown that sugar-based biodegradable polyurethane polymers exhibit outstanding properties as polymer-matrix for gold nanoparticles composites. These materials could reach exceptional stabilization levels, and demonstrated potential as novel robust inks for Inkjet based Printing. Furthermore, a physical comparison among different polymers is discussed based on stability and printability experiments to search for the best ink candidate. The University of Seville logo was printed by employing those inks, and the presence of gold was confirmed by ToF-SIMS. This approach has the potential to open new routes and applications for fabrication of enhanced biomedical nanometallic-sensors using stabilized AuNP.Spanish Ministerio de Economía y Competitividad MINECO, (Grants Nos. CTQ2016- 78703-P and MAT2016-78703-P)Junta de Andalucía (Consolidation Grant for Research Group FQM135 and 2017/FQM-386, P-2018/809)University of Seville (V y VI Plan Propio PP2016-5937

FOXQ1 promotes proliferation and metastasis of epithelial ovarian cancer via activation of SIRT1/NRF2 signaling pathway

Purpose: To investigate the role of FOXQ1 in the progression of epithelial ovarian cancer and the underlying mechanism. Methods: Forkhead Box Q1 overexpression was evaluated by quantitative reverse-transcription (qRTPCR) in clinical epithelial ovarian cancer samples and cell lines. Proliferation, migration, and invasion of cancer cells were determined using CCK8, wound healing and transwell assay. Results: FOXQ1 depletion inhibited the proliferation, migration, and invasion of `epithelial ovarian cancer cells. Moreover, FOXQ1 overexpression increased the amount of cells in S phase of the cell cycle, and FOXQ1 knockdown arrested cells inG1 phase. Results from ChIP and luciferase reporter assays showed that FOXQ1 was able to bind SIRT1 promoters. In addition, it was involved in sustaining the stability of nuclear factor erythroid derived 2-like 2 (NRF2) by decreasing its acetylation (p < 0.01), which was mediated by SIRT1. The data also demonstrated that NRF2 promotes proliferation, migration, and invasion of cancer cells upon FOXQ1 overexpression. Conclusion: Forkhead Box Q1 contributes to the progression of epithelial ovarian cancer partly via SIRT1/NRF2 signaling pathway, this highlighting a novel strategy for treating epithelial ovarian cancer

An investigation of the behavior of solvent based polycaprolactone ink for material jetting

An initial study of processing bioresorbable polycaprolactone (PCL) through material jetting was conducted using a Fujifilm Dimatix DMP-2830 material printer. The aim of this work was to investigate a potential solvent based method of jetting polycaprolactone. Several solvents were attempt to prepared PCL solvent based ink and 1, 4-dioxane was chosen with the consideration of both solubility and safety. The morphology of PCL formed under different substrate temperatures, droplet spacings were investigated. Multi-layer PCL structures were printed and characterized. This work shows that biodegradable polycaporlactone can be processed through material jetting by dissolving it

Ink-jet 3D printing as a strategy for developing bespoke non-eluting biofilm resistant medical devices

Chronic infection as a result of bacterial biofilm formation on implanted medical devices is a major global healthcare problem requiring new biocompatible, biofilm-resistant materials. Here we demonstrate how bespoke devices can be manufactured through ink-jet-based 3D printing using bacterial biofilm inhibiting formulations without the need for eluting antibiotics or coatings. Candidate monomers were formulated and their processability and reliability demonstrated. Formulations for in vivo evaluation of the 3D printed structures were selected on the basis of their in vitro bacterial biofilm inhibitory properties and lack of mammalian cell cytotoxicity. In vivo in a mouse implant infection model, Pseudomonas aeruginosa biofilm formation on poly-TCDMDA was reduced by ∼99% when compared with medical grade silicone. Whole mouse bioluminescence imaging and tissue immunohistochemistry revealed the ability of the printed device to modulate host immune responses as well as preventing biofilm formation on the device and infection of the surrounding tissues. Since 3D printing can be used to manufacture devices for both prototyping and clinical use, the versatility of ink-jet based 3D-printing to create personalised functional medical devices is demonstrated by the biofilm resistance of both a finger joint prosthetic and a prostatic stent printed in poly-TCDMDA towards P. aeruginosa and Staphylococcus aureus.Engineering and Physical Sciences Research Council del Reino Unido-EP/I033335/2, EP/N024818/1, EP/P031684/1 y EP/L015072/1Wellcome Trust Senior Investigator Joint Awards del Reino Unido-103882/Z/14/Z y 103884/Z/14/

Inkjet printing of polyimide insulators for the 3D printing of dielectric materials for microelectronic applications

In this article, we report the first continuous fabrication of inkjet-printed polyimide films, which were used as insulating layers for the production of capacitors. The polyimide ink was prepared from its precursor poly(amic) acid, and directly printed on to a hot substrate (at around 160 °C) to initialize a rapid thermal imidization. By carefully adjusting the substrate temperature, droplet spacing, droplet velocity, and other printing parameters, polyimide films with good surface morphologies were printed between two conducting layers to fabricate capacitors. In this work, the highest capacitance value, 2.82 ± 0.64 nF, was achieved by capacitors (10 mm × 10 mm) with polyimide insulating layers thinner than 1 μm, suggesting that the polyimide inkjet printing approach is an efficient way for producing dielectric components of microelectronic devices. © 2016 The Authors Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43361

Inkjet 3D Printing of Polymers Resistant to Fungal Attachment

Inkjet 3D printing is an additive manufacturing method that allows the user to produce a small batch of customized devices for comparative study versus commercial products. Here, we describe the use of a commercial 2D ink development system (Dimatix material printing) to manufacture small batches of 3D medical or other devices using a recentlycharacterized fungal anti-attachment material. Such printed devices may resist problems that beset commercial medical products due to colonization by the fungal pathogen Candida albicans. By sequentially introducing the cross-section bitmapsof the product's CAD model and elevating the print head height usingthe auto-clicking script, we were able to createcomplex self-support geometries with the 2D ink development system. The use of this protocol allows researchers to produce a small batch of specimens for characterization fromonly a few grams of raw material. Additionally, wedescribe the testing of manufactured specimens for fungal anti-attachment. In comparisonwith most commercial AM systems, which require at least a few hundred grams ofink for printing trials, our protocol is well suited for smaller-scale production in material studies

Additive manufacture of three dimensional nanocomposite based objects through multiphoton fabrication

Three dimensional structures prepared from a gold-polymer composite formulation have been fabricated using multiphoton lithography. In this process, gold nanoparticles were simultaneously formed through photoreduction whilst polymerisation of two possible monomers was promoted. The monomers, trimethylopropane triacrylate (TMPTA) and pentaerythritol triacrylate (PETA) were mixed with a gold salt, but it was found that the addition of a Ruthenium (II) complex enhanced both the geometrical uniformity and integrity of the polymerized / reduced material, enabling the first production of 3D gold-polymer structures by single step multiphoton lithography

Enhancing the 3D printing fidelity of vat photopolymerization with machine learning-driven boundary prediction

Like many pixel-based additive manufacturing (AM) techniques, digital light processing (DLP) based vat pho-topolymerization faces the challenge that the square pixel based processing strategy can lead to zigzag edges especially when feature sizes come close to single-pixel levels. Introducing greyscale pixels has been a strategy to smoothen such edges, but it is a challenging task to understand which of the many permutations of projected pix-els would give the optimal 3D printing performance. To address this challenge, a novel data acquisition strategy based on machine learning (ML) principles is proposed, and a training routine is implemented to reproduce the smallest shape of an intended 3D printed object. Through this approach, a chessboard patterning strategy is developed along with an automated data refining and augmentation workflow, demonstrating its efficiency and effectiveness by reducing the deviation by around 30%

Author Correction: Additive manufacture of complex 3D Au-containing nanocomposites by simultaneous two-photon polymerisation and photoreduction

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