The field of 3D printing, also known as additive manufacturing (AM), is developing rapidly in both academic and industrial research environments. New materials and printing technologies, which enable ...rapid and multimaterial printing, have given rise to new applications and utilizations. However, the main bottleneck for achieving many more applications is the lack of materials with new physical properties. Here, some of the recent reports on novel materials in this field, such as ceramics, glass, shape‐memory polymers, and electronics, are reviewed. Although new materials have been reported for all three main printing approaches—fused deposition modeling, binder jetting or laser sintering/melting, and photopolymerization‐based approaches, apparently, most of the novel physicochemical properties are associated with materials printed by photopolymerization approaches. Furthermore, the high resolution that can be achieved using this type of 3D printing, together with the new properties, has resulted in new implementations such as microfluidic, biomedical devices, and soft robotics. Therefore, the focus here is on photopolymerization‐based additive manufacturing including the recent development of new methods, novel monomers, and photoinitiators, which result in previously inaccessible applications such as complex ceramic structures, embedded electronics, and responsive 3D objects.
Photopolymerization‐based 3D printing materials have been reported widely in recent years. Various materials such as hydrogels, ceramics, and responsive polymers, along with new applications of these materials and methods are described.
This paper introduces a novel method of 3D designing and 3D printing of a hybrid orthodontic tooth-borne personalized distalizer for treatment of unilateral Class II malocclusion. Research objectives ...were to clinically utilize 3D printed distalizers, appraise feasibility of this technique and compare two different biocompatible photopolymers (white and transparent). Frequency of distalizers' debonding and patients' aesthetical perception was evaluated on the set of 12 complete orthodontic treatments. The mean duration of treatment period with a bonded distalizer was 6.4 months. All cases were adults with unilateral Class II malocclusion managed with a hybrid approach as a part of Invisalign
comprehensive treatment. Results showed that such perspective practice is feasible for 3D design and in-office 3D printing of a personalized distalizer. Results also showed no clinically significant differences between both studied biopolymers. The paper discusses an evaluation of such personalized distalizer functionality with regard to the current state of the art and compares to conventional prefabricated alternatives like a Carriere
Distalizer™ appliance. Research showed a preference of patients towards transparent biocompatible photopolymer instead of the white A2 shade. The paper concludes that additive manufacturing from dental resins is a viable method in personalization and in-office 3D printing of orthodontic auxiliaries, particularly distalizers. New materials for orthodontic 3D printing endow enhanced individualization, thus more efficient treatment.
Since the first report of 3D printed biodegradable structures by stereolithography, vat photopolymerization has shown great potential in the fabrication of medical implants and devices. Despite its ...superior printing quality and manufacturing speed, the development of biodegradable devices by this technique remains challenging. This results from the conflicting viscosity requirements for the printing resins, i.e., low viscosity is required for high‐resolution 3D printing, whereas high viscosity is often needed to provide high mechanical strength. Recently emerging photopolymerization‐based 3D printing techniques, including heat‐assisted digital light processing (DLP) and volumetric printing, have brought new hope to the field. With its tolerance to high viscosity resins, heat‐assisted DLP enables the fabrication of complex, personalizes architectures from biodegradable photopolymers that are not printable by conventional printing techniques. On the other hand, volumetric printing, which abandons the layer‐by‐layer printing principle and thus circumvents the dependence on low viscosity resins, could be highly beneficial for the 3D printing of biodegradable devices. This perspective evaluates the key challenges associated with biodegradable photopolymers used in the 3D printing of medical implants and devices. One focuses on their chemical structures and physical properties and discusses future directions offered by these emerging techniques.
The key challenges associated with biodegradable photopolymers for 3D printed medical implants and devices are analyzed, and the new opportunities brought by recently emerged techniques in particular heat‐assisted vat photopolymerization and volumetric 3D printing are explored. An outlook on the possible future research directions involving material design and technical progress is also provided.
Projection micro stereolithography (PμSL) is a high-resolution (up to 0.6 μm) 3D printing technology based on area projection triggered photopolymerization, and capable of fabricating complex 3D ...architectures covering multiple scales and with multiple materials. This paper reviews the recent development of the PμSL based 3D printing technologies, together with the related applications. It introduces the working principle, the commercialized products, and the recent multiscale, multimaterial printing capability of PμSL as well as some functional photopolymers that are suitable to PμSL. This review paper also summarizes a few typical applications of PμSL including mechanical metamaterials, optical components, 4D printing, bioinspired materials and biomedical applications, and offers perspectives on the directions of the further development of PμSL based 3D printing technology.
Phenanthraquinone-doped polymethyl methacrylate (PQ/PMMA) photopolymers are considered to be the most promising holographic storage media due to their unique properties, such as high stability, a ...simple preparation process, low price, and volumetric shrinkage. This paper reviews the development process of PQ/PMMA photopolymers from inception to the present, summarizes the process, and looks at the development potential of PQ/PMMA in practical applications.
Volume reflection hologram-based sensors are designed to visibly change colour in response to a target stressor or analyte. However, reflection holograms fabricated in thick photopolymer films are ...highly angularly selective, making these sensors challenging to view and interpret by non-experts. Here, the use of speckle holography to improve the visibility of reflection holograms is presented. A novel recording approach combining speckle recording techniques with Denisyuk reflection recording geometry is described. The recorded speckle reflection grating operates as a series of multiplexed reflection gratings with a range of spatial frequencies, capable of reflecting light at a wider range of angles. A comparative study of the angular and wavelength selectivity of speckle and standard reflection gratings was conducted. The FWHM of the angular selectivity curves of the speckle reflection gratings is doubled (4°) in comparison to standard 4500 lines/mm reflection gratings (2°). The wavelength selectivity FWHM is also doubled from 4.2 to 8.6 nm. The comparative ability of the speckle and standard reflection gratings to act as colour-changing compressional pressure sensors in the 0.88-5.31 MPa range is described. Finally, we present a prototype reflection hologram viewer which enables the easy observation of angularly specific reflection holograms by non-experts.
To avoid mixing of the undesired frequencies in a free‐space, the point sources of gratings, defined by a spatially varying refractive index, should be sinusoidally rather than binarily arranged. ...This long‐lasting but gold standard lesson attainable from a classical Fourier optics, however, is underutilized in the practical materialization of gratings, mainly because most of the fabrication methods, developed thus far, are intrinsically compatible with a binary rather than sinusoidal grating. Recently, such design concept of optical Fourier elements has been implemented into the real surface gratings (referred to as optical Fourier surfaces) by taking advantage of advanced nanofabrication, whereas their volumetric equivalents (optical Fourier volumes, OFVs) have yet to be conceptually and experimentally elucidated. In this work, the key characteristics of OFVs and their structural requirements are systematically exploited with the assistance of analytical and numerical calculations. Especially, the dynamic range and thickness of volume gratings, required for OFVs, are newly defined. Given these theoretical blueprints, both the holographic photopolymers and photoaddressable polymers are then revisited and they are experimentally validated as easy‐to‐craft mediums of OFVs. The landscape of volume gratings is extended by providing an integrative pipeline of OFVs across their theoretical design and practical materialization.
The concept of optical Fourier volumes (OFVs) has come to the fore. In this work, the distinct concept of OFVs is elucidated with the assistance of an integrative pipeline across the analytical and numerical calculations; then, both holographic photopolymers and photoaddressable polymers are experimentally validated as the recording mediums of OFVs.
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