Photopolymerization in 3D Printing
20 Feb 2019-Vol. 1, Iss: 4, pp 593-611
TL;DR: The field of 3D printing is continuing its rapid development in both academic and industrial research environments as mentioned in this paper, which offers flexibility over the final properties of the 3D printed materials (such as optical, chemical and mechanical properties) using versatile polymer chemistry.
Abstract: The field of 3D printing is continuing its rapid development in both academic and industrial research environments. The development of 3D printing technologies has opened new implementations in rapid prototyping, tooling, dentistry, microfluidics, biomedical devices, tissue engineering, drug delivery, etc. Among different 3D printing techniques, photopolymerization-based process (such as stereolithography and digital light processing) offers flexibility over the final properties of the 3D printed materials (such as optical, chemical, and mechanical properties) using versatile polymer chemistry. The strategy behind the 3D photopolymerization is based on using monomers/oligomers in liquid state (in the presence of photoinitiators) that can be photopolymerized (via radical or cationic mechanism) upon exposure to light source of different wavelengths (depending on the photoinitiator system). An overview of recent evolutions in the field of photopolymerization-based 3D printing and highlights of novel 3D print...
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TL;DR: In this article, three photopolymerization technologies, namely, stereolithography (SLA), digital light processing (DLP), and continuous digital light process (CDLP), are reviewed.
Abstract: Additive manufacturing (3D printing) has significantly changed the prototyping process in terms of technology, construction, materials, and their multiphysical properties. Among the most popular 3D printing techniques is vat photopolymerization, in which ultraviolet (UV) light is deployed to form chains between molecules of liquid light-curable resin, crosslink them, and as a result, solidify the resin. In this manuscript, three photopolymerization technologies, namely, stereolithography (SLA), digital light processing (DLP), and continuous digital light processing (CDLP), are reviewed. Additionally, the after-cured mechanical properties of light-curable resin materials are listed, along with a number of case studies showing their applications in practice. The manuscript aims at providing an overview and future trend of the photopolymerization technology to inspire the readers to engage in further research in this field, especially regarding developing new materials and mathematical models for microrods and bionic structures.
191 citations
04 Jun 2020
TL;DR: This review paper summarizes a few typical applications of P μSL 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.
Abstract: 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.
174 citations
Cites background from "Photopolymerization in 3D Printing"
...The photopolymerization is a free radical based polymerization, and includes four main steps: radical generation, initiation, propagation, and termination [62, 63]....
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TL;DR: In this work, crosslinking methods used in 3D bioprinting studies are reviewed, parameters that affect bioink chemistry are discussed, and the potential toward improving crossl linking outcomes and construct performance is highlighted.
Abstract: Three-dimensional (3D) bioprinting has recently advanced as an important tool to produce viable constructs that can be used for regenerative purposes or as tissue models. To develop biomimetic and sustainable 3D constructs, several important processing aspects need to be considered, among which crosslinking is most important for achieving desirable biomechanical stability of printed structures, which is reflected in subsequent behavior and use of these constructs. In this work, crosslinking methods used in 3D bioprinting studies are reviewed, parameters that affect bioink chemistry are discussed, and the potential toward improving crosslinking outcomes and construct performance is highlighted. Furthermore, current challenges and future prospects are discussed. Due to the direct connection between crosslinking methods and properties of 3D bioprinted structures, this Review can provide a basis for developing necessary modifications to the design and manufacturing process of advanced tissue-like constructs in future.
150 citations
TL;DR: Improved tissue adhesion of the bioinspired MN allows for more stable and robust performance for drug delivery, biofluid collection, and biosensing.
143 citations
TL;DR: An overview of the vat polymerization techniques, their unique applications in the fields of drug delivery and medical device fabrication, material examples and the advantages they provide within healthcare, is provided.
136 citations
References
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TL;DR: The use of photoinitiated polymerization is continuously growing in industry as reflected by the large number of applications in not only conventional areas such as coatings, inks, and adhesives but also high-tech domains, optoelectronics, laser imaging, stereolithography, and nanotechnology as mentioned in this paper.
Abstract: The use of photoinitiated polymerization is continuously growing in industry as reflected by the large number of applications in not only conventional areas such as coatings, inks, and adhesives but also high-tech domains, optoelectronics, laser imaging, stereolithography, and nanotechnology. In this Perspective, the latest developments in photoinitiating systems for free radical and cationic polymerizations are presented. The potential use of photochemical methods for step-growth polymerization is also highlighted. The goal is, furthermore, to show approaches to overcome problems associated with the efficiency, wavelength flexibility, and environmental and safety issues in all photoinitiating systems for different modes of activation. Much progress has been made in the past 10 years in the preparation of complex and nano-structured macromolecules by using photoinitiated polymerizations. Thus, the new and emerging applications of photoinitiated polymerizations in the field of biomaterials, surface modific...
1,082 citations
TL;DR: This paper, presenting a first-time comprehensive review of EBB, discusses the current advancements in EBB technology and highlights future directions to transform the technology to generate viable end products for tissue engineering and regenerative medicine.
1,048 citations
TL;DR: This Perspective presents recent advances in macromolecular engineering enabled by ATRP with emphasis on various catalytic/initiation systems that use parts-per-million concentrations of Cu catalysts and can be run in environmentally friendly media, e.g., water.
Abstract: This Perspective presents recent advances in macromolecular engineering enabled by ATRP. They include the fundamental mechanistic and synthetic features of ATRP with emphasis on various catalytic/initiation systems that use parts-per-million concentrations of Cu catalysts and can be run in environmentally friendly media, e.g., water. The roles of the major components of ATRP—monomers, initiators, catalysts, and various additives—are explained, and their reactivity and structure are correlated. The effects of media and external stimuli on polymerization rates and control are presented. Some examples of precisely controlled elements of macromolecular architecture, such as chain uniformity, composition, topology, and functionality, are discussed. Syntheses of polymers with complex architecture, various hybrids, and bioconjugates are illustrated. Examples of current and forthcoming applications of ATRP are covered. Future challenges and perspectives for macromolecular engineering by ATRP are discussed.
985 citations
TL;DR: A water soluble lithium acylphosphinate salt is evaluated for its ability to polymerize diacrylated poly(ethylene glycol) (PEGDA) monomers rapidly into hydrogels, while maintaining high viability during direct encapsulation of cells.
948 citations
TL;DR: Despite the obvious, practical advantages of visible light as an “infinitely available” promoter for chemical synthesis, the simple inability of most organic molecules to absorb light in the visible range of the spectrum has greatly limited the potential applications of photochemical reactions.
Abstract: The increasing need for more efficient synthetic methods and sustainable processes can be seen as a major driving force for new inventions; it also stimulates the creative rethinking of known concepts, which, in turn, will lead to the development of innovative chemistry. For example, starting from the challenge to mimic and understand enzymatic transformations, organocatalysis has now become an important tool in modern organic synthesis with new reactivity that complements that of enzyme and metal catalysis. As early as the beginning of the 20th century, photochemistry had already attracted the attention of (organic) chemists. But recent years have seen broader interest in photochemical transformations because of the generally mild conditions required for substrate activation—ideally light alone—and their suitability for “green reactions”. While classical photochemical steps have found notable applications in synthesis and the direct transformation of light into electric energy (photovoltaics) can already be considered a highly developed research field, efforts in photocatalysis have mainly targeted the development of artificial photosynthesis systems for the conversion of solar energy into storable chemical fuels. However, despite the obvious, practical advantages of visible light as an “infinitely available” promoter for chemical synthesis, the simple inability of most organic molecules to absorb light in the visible range of the spectrum has greatly limited the potential applications of photochemical reactions. One major strategy to address this drawback and to develop new efficient processes using visible light is the use of photosensitizers and photocatalysts. Upon irradiation, molecules are converted into their photoexcited states, which are chemically more reactive because of the significantly altered electronic distribution. Apart from following various common physical decay pathways, these photoexcited states can undergo chemical “deactivation” processes, which are either unimolecular and correspond to classical photochemical transformations (isomerizations, rearrangements, etc.) or proceed in a bimolecular manner. The interactions with other species range from bimolecular reactions such as photocycloadditions to quenching processes. Here, the most important pathways are energy-transfer reactions and electron-transfer reactions; both play a crucial role as indirect initiators for all types of photocatalytic reactions. Photoredox catalysis relies on the general property of excited states to be both more easily reduced as well as more easily oxidized than their corresponding ground states, and so the photocatalyst can serve either as an electron donor or an electron acceptor to be regenerated in the catalytic cycle (Scheme 1). The photocatalyst undergoes two distinct electron-transfer steps; both the “quenching” and the “regenerative” electron transfer can be productive with respect to a desired chemical transformation. Ideally, the two electrontransfer processes are connected by the substrates or intermediates of the catalyzed reaction and therefore do not require any sacrificial electron donor or acceptor.
831 citations