Inkjet drug printing onto contact lenses: Deposition optimisation and non-invasive dose verification

Inkjet printing has the potential to advance the treatment of eye diseases by printing drugs on demand onto contact lenses for localised delivery and personalised dosing, while near-infrared (NIR) spectroscopy can further be used as a quality control method for quantifying the drug but has yet to be demonstrated with contact lenses. In this study, a glaucoma therapy drug, timolol maleate, was successfully printed onto contact lenses using a modified commercial inkjet printer. The drug-loaded ink prepared for the printer was designed to match the properties of commercial ink, whilst having maximal drug loading and avoiding ocular inflammation. This setup demonstrated personalised drug dosing by printing multiple passes. Light transmittance was found to be unaffected by drug loading on the contact lens. A novel dissolution model was built, and in vitro dissolution studies showed drug release over at least 3 h, significantly longer than eye drops. NIR was used as an external validation method to accurately quantify the drug dose. Overall, the combination of inkjet printing and NIR represent a novel method for point-of-care personalisation and quantification of drug-loaded contact lenses

Hiding patterns with daylight fluorescent inks

We propose a method for hiding patterns within printed images by making use of classical and of two daylight fluorescent magenta and yellow inks. Under the D65 illuminant we establish in the CIELAB space the gamut of a classical cmyk printer and the gamut of the same printer using a combination of classical inks with daylight fluorescent inks. These gamuts show that a significant part of the classical ink gamut can be reproduced by combining classical inks with daylight fluorescent inks. By printing parts of images with a combination of classical and daylight fluorescent inks instead of using classical inks only, we can hide security patterns within printed images. Under normal daylight, we do not see any difference between the parts printed with classical inks only and the parts printed with daylight fluorescent inks and classical inks. By changing the illumination, e.g. by viewing the printed image under a tungsten lamp or under a UV lamp, the daylight fluorescent inks change their colors and reveal the security pattern formed by combinations of classical inks and of daylight fluorescent inks

How Can We Provide Additively Manufactured Parts with a Fingerprint? A Review of Tagging Strategies in Additive Manufacturing

Additive manufacturing (AM) is rapidly evolving from “rapid prototyping” to “industrial production”. AM enables the fabrication of bespoke components with complicated geometries in the high-performance areas of aerospace, defence and biomedicine. Providing AM parts with a tagging feature that allows them to be identified like a fingerprint can be crucial for logistics, certification and anti-counterfeiting purposes. Whereas the implementation of an overarching strategy for the complete traceability of AM components downstream from designer to end user is, by nature, a cross-disciplinary task that involves legal, digital and technological issues, materials engineers are on the front line of research to understand what kind of tag is preferred for each kind of object and how existing materials and 3D printing hardware should be synergistically modified to create such tag. This review provides a critical analysis of the main requirements and properties of tagging features for authentication and identification of AM parts, of the strategies that have been put in place so far, and of the future challenges that are emerging to make these systems efficient and suitable for digitalisation. It is envisaged that this literature survey will help scientists and developers answer the challenging question: “How can we embed a tagging feature in an AM part?”

Characterisation of Implant Supported Soft Tissue Prostheses Produced with 3D Colour Printing Technology

The numbers of patients needing facial prostheses has increased in the last few decades due to improving cancer survival rates. The many limitations of the handmade prostheses together with rapid expansion of prototyping in all directions, particularly in producing human anatomically accurate parts, have raised the question of how to employ this technology for rapid manufacturing of facial soft tissue prostheses. The idea started to grow and the project was implemented based on CAD/CAM principles – additive manufacturing technology, by employing layered fabrication of facial prostheses from starch powder and a water based binder and infiltrated with a silicone polymer (SPIS). The project aimed to produce a facial prosthesis by using 3D colour printing, which would match the patient’s skin shade and have the desirable mechanical properties, through a relatively low cost process that would be accessible to the global patient community. This was achieved by providing a simple system for data capture, design and reproducible method of manufacture with a clinically acceptable material. The prosthesis produced has several advantages and few limitations when compared to existing products/prostheses made from silicone polymer (SP). The mechanical properties and durability were not as good as those of the SP made prosthesis but they were acceptable, although the ideal properties have yet to be identified. Colour reproduction and colour matching were more than acceptable, although the colour of the SPIS parts was less stable than the SP colour under natural and accelerated weathering conditions. However, it is acknowledged that neither of the two methods used represent the natural life use on patients and the deficiencies demonstrated in terms of mechanical properties and colour instability were partially inherent in the methodology used, as the project was still at the developmental stage and it was not possible to apply real life tests on patients. Moreover, deficiencies in mechanical and optical properties were probably caused by the starch present, which was used as a scaffold for the SP. Furthermore, a suitable retention system utilising existing components was designed and added to the prosthesis. This enabled the prosthesis to be retained by implants with no need for the addition of adhesive. This would also help to prolong the durability and life span of the prosthesis. The capability of the printer to produce skin shades was determined and it was found that all the skin colours measured fall within the range of the 3D colour printer and thereby the printer was able to produce all the colours required. Biocompatibility was also acceptable, with a very low rate of toxicity. However, no material is 100% safe and each material has a certain range of toxicity at certain concentrations. At this stage of the project, it can be confirmed that facial prostheses were successfully manufactured by using 3D colour printing to match the patient’s skin shade, using biocompatible materials and having the desirable mechanical properties. Furthermore, the technology used enabled prostheses to be produced in a shorter time frame and at a lower cost than conventional SP prostheses. They are also very lightweight, easier to use and possibly more comfortable for the patients. Moreover, this technology has the capability of producing multiple prostheses at the time of manufacture at reduced extra cost, whilst the data can be saved and can be utilised/modified for producing further copies in the future without having to going through all the steps involved with handmade prostheses. Based on the mechanical properties and colour measurements the prostheses will have a finite service life and the recommendation is that these prostheses will need replacing every 6 to 12 months, depending on how the patient handles and maintains the prostheses and whether the prosthesis is being used as an interim or definitive prosthesis. This was largely comparable to existing prostheses but without the time and cost implications for replacement. However, it is acknowledged that further investigations and clinical case studies are required to investigate the “real life” effect on the prostheses and to get feedback from the patients in order to make appropriate improvements to the mechanical properties and the durability of the prosthesis

Engineering three-dimensional bone macro-tissues by guided fusion of cell spheroids

Introduction: Bioassembly techniques for the application of scaffold-freetissue engineering approaches have evolved in recent years towardproducing larger tissue equivalents that structurally and functionally mimicnative tissues. This study aims to upscale a 3-dimensional bone in-vitromodel through bioassembly of differentiated rat osteoblast (dROb) spheroidswith the potential to develop and mature into a bone macrotissue.Methods: dROb spheroids in control and mineralization media at differentseeding densities (1 × 104, 5 × 104, and 1 × 105 cells) were assessed for cellproliferation and viability by trypan blue staining, for necrotic core byhematoxylin and eosin staining, and for extracellular calcium by Alizarin redand Von Kossa staining. Then, a novel approach was developed tobioassemble dROb spheroids in pillar array supports using a customizedbioassembly system. Pillar array supports were custom-designed and printedusing Formlabs Clear Resin® by Formlabs Form2 printer. These supports wereused as temporary frameworks for spheroid bioassembly until fusionoccurred. Supports were then removed to allow scaffold-free growth andmaturation of fused spheroids. Morphological and molecular analyses wereperformed to understand their structural and functional aspects.Results: Spheroids of all seeding densities proliferated till day 14, andmineralization began with the cessation of proliferation. Necrotic core sizeincreased over time with increased spheroid size. After the bioassembly ofspheroids, the morphological assessment revealed the fusion of spheroidsover time into a single macrotissue of more than 2.5 mm in size with mineralformation. Molecular assessment at different time points revealed osteogenicmaturation based on the presence of osteocalcin, downregulation of Runx2(p < 0.001), and upregulated alkaline phosphatase (p < 0.01).Discussion: With the novel bioassembly approach used here, 3D bonemacrotissues were successfully fabricated which mimicked physiological osteogenesis both morphologically and molecularly. This biofabricationapproach has potential applications in bone tissue engineering,contributing to research related to osteoporosis and other recurrentbone ailments

Microextrusion 3D Printing of Optical Waveguides and Microheaters

The drive for smaller and more compact devices presents several challenges in materials and fabrication strategies. Although photolithography is a well-developed method for creating microdevices, the disparate requirements in fabrication strategies, material choices, equipment and process complexities have limited its applications. Microextrusion printing (μEP) provides a promising alternative for microfabrication. Compared to the traditional techniques, the attractions lie in the wide range of printable material choice, greater design freedom, fewer processing steps, lower cost for customized production, and the plurality of compatible substrates. However, while extrusion-based 3D printing processes have been successfully applied at the macroscale, this seeming simplicity belies the dynamic complexities needed for consistent, repeatable, and cost-effective printing at the microscale. The fundamental understanding of the microextrusion printing process is still lacking. One primary goal of this dissertation, therefore, is to develop the fundamental understanding of μEP. This study elucidates the underlying principles of this printing technique, offering an overall roadmap - stepwise guide for successful printing based on both results in the literature and our experimental tests. The primary motivation is to provide users at both the research and industrial platforms with the requisite knowledge base needed for adapting μEP for microfabrication. Ultimately, this understanding, optimization of materials properties, and process parameters dictate the resolution and quality of the printed features. Following the improved understanding of microextrusion printing, two complementary goals were set. First, in order to test and validate the applicability the framework, a high-resolution microextrusion 3D printer was designed and implemented to enable high precision printing of microdevices and microstructures. Second, taking advantage of the guiding framework and printing platform, printing of novel materials and devices including flexible optics and a high-temperature microheater were explored and demonstrated. One common thread is observed throughout this work, that is, the development of the fundamental understanding of microextrusion 3D printing and its application for creating functional microdevices and structures. This work opens new possibilities and versatile approach for low-cost patterning of materials and functional devices

Automatic Media Identification

Català: Identificació automàtica de paper basat en mesures espectrals i de radiació difusa.Castellano: Identificación del tipo de papel basado en medidas espectrales y de radiación difusa.Anglés: Media type identification based in spectral and diffuse measurements

New Trends in 3D Printing

A quarter century period of the 3D printing technology development affords ground for speaking about new realities or the formation of a new technological system of digital manufacture and partnership. The up-to-date 3D printing is at the top of its own overrated expectations. So the development of scalable, high-speed methods of the material 3D printing aimed to increase the productivity and operating volume of the 3D printing machines requires new original decisions. It is necessary to study the 3D printing applicability for manufacturing of the materials with multilevel hierarchical functionality on nano-, micro- and meso-scales that can find applications for medical, aerospace and/or automotive industries. Some of the above-mentioned problems and new trends are considered in this book