Emerging Technologies for Multiphoton Writing and Reading of Polymeric Architectures for Biomedical Applications.

Objective: Two-photon polymerization (TPP) utilizes an optical nonlinear absorption process to initiate the polymerization of photopolymerizable materials. To date, it is the only technique capable of fabricating complex 3D microstructures with finely adjusted geometry on the cell and sub-cell scales. TPP shows a very promising potential in biomedical applications related to high-resolution features, including drug delivery, tissue engineering, microfluidic devices, and so forth. Therefore, it is of high significance to grasp the global scientific achievements in this field. An analysis of publications concerning the applications of TPP in the biomedical field was performed, and the knowledge domain, research hotspots, frontiers, and research directions in this topic were identified according to the research results. Methods: The publications concerning TPP applications in biomedical field were retrieved from WoSCC between 2003 and 2022, Bibliometrics and visual analysis employing CiteSpace software and R-language package Bibliometrix were performed in this study. Results: A total of 415 publications regarding the TPP applications in the biomedical field were retrieved from WoSCC, including 377 articles, and 38 review articles. The studies pertaining to the biomedical applications of TPP began back in 2003 and showed an upward trend constantly. Especially in the recent 5 years, studies of TPP in biomedical field have increased rapidly, with the number of publications from 2017 to 2021 accounting for 52.29% of the total. In terms of output, China was the leading country and Chinese Acad Sci, Tech Inst Phys and Chem was the leading institution. The United States showed the closest cooperation with other countries. ACS applied materials and interfaces was the most prolific journal (n = 13), followed by Biofabrication (n = 11) and Optics express (n = 10). The journals having the top cited papers were Biomaterials, Advanced materials, and Applied physic letters. The most productive author was Aleksandr Ovsianikov (27 articles). Meanwhile, researchers who had close cooperation with other researchers were also prolific authors. “cell behavior”, " (tissue engineering) scaffolds”, “biomaterials,” and “hydrogel” were the main co-occurrence keywords and “additional manufacturing”, “3D printing,” and “microstructures” were the recent burst keywords. The Keyword clusters, “stem cells,” and “mucosal delivery”, appeared recently. A paper reporting unprecedented high-resolution bull models fabricated by TPP was the most locally cited reference (cited 60 times). “Magnetic actuation” and “additive manufacturing” were recently co-cited reference clusters and an article concerning ultracompact compound lens systems manufactured by TPP was the latest burst reference. Conclusion: The applications of TPP in biomedical field is an interdisciplinary research topic and the development of this field requires the active collaboration of researchers and experts from all relevant disciplines. Bringing up a better utilization of TPP as an additive manufacturing technology to better serve the biomedical development has always been the research focus in this field. Research on stem cells behaviors and mucosal delivery based on microstructures fabricated using TPP were becoming new hotspots. And it can be predicted that using TPP as a sourcing technique to fabricate biomedical-related structures and devices is a new research direction. In addition, the research of functional polymers, such as magnetic-driven polymers, was the frontier topic of TPP biomedical applications.

The life of human beings is moving at a breakneck pace, with a fast-moving life demanding the need for devices for use in biomedical applications, which attracts the interested researcher to work on ensuring novel breakthroughs. Processing of biomaterials is one of the key factors that will exert an influence on impacting the attributes of a biomaterial. Additive manufacturing is one of the promising routes by which layer-by-layer creation of parts takes place from a computer-aided design (CAD) file. Parts that cannot or are difficult to manufacture by other processing routes can be easily manufactured using the technique of additive manufacturing (AM). Parts, such as (i) stents, (ii) customized prosthetics, (iii) organs, and (iv) implants can be easily manufactured using the technique of additive manufacturing (AM). With noticeable advances in the domain specific to additive manufacturing, the biomedical field is being revolutionized, and viable solutions to difficult problems are being put forth with ease, and the resultant by-products offer a combination of acceptable to good properties. The key benefits of the technique of additive manufacturing (AM) are low cost, minimal material waste, and enhanced product reliability. This study explores recent developments in both alloys and composite materials processed by the techniques of additive manufacturing for selection and use in biomedical applications. This review provides a highlight of the different additive manufacturing techniques with specific reference to biomedical applications and additive manufacturing of titanium alloys, the Co-Cr alloy, the magnesium alloys and their composite counterparts. Multidisciplinary research will be required to meet and overcome any and all obstacles while concurrently fulfilling the potential of additive manufacturing (AM) in the years ahead.

Two-photon polymerization (TPP) is an additive manufacturing technique with micron-scale resolution that is rapidly gaining ground for a range of biomedical applications. TPP is particularly attractive for the creation of microscopic three-dimensional structures in biocompatible and noncytotoxic resins. Here, TPP is used to develop microfluidic interfaces which provide chronic fluidic access to the brain of preclinical research models. These microcatheters can be used for either convection-enhanced delivery (CED) or for the repeated collection of liquid biopsies. In a brain phantom, infusions with the micronozzle result in more localized distribution clouds and lower backflow compared to a control catheter. In mice, the delivery interface enables faster, more precise, and physiologically less disruptive fluid injections. A second microcatheter design enables repeated, longitudinal sampling of cerebrospinal fluid (CSF) over time periods as long as 250 days. Moreover, further in vivo studies demonstrate that the blood-CSF barrier is intact after chronic implantation of the sampling interface and that samples are suitable for downstream molecular analysis for the identification of nucleic acid- or peptide-based biomarkers. Ultimately, the versatility of this fabrication technique implies a great translational potential for simultaneous drug delivery and biomarker tracking in a range of human neurological diseases.

Additive manufacturing (AM) plays a key role in fabricating micro and nanosensors because it can produce intricate shapes that are challenging to fabricate with conventional methods. AM offers unparalleled design flexibility and precision, particularly in the fields of diagnostics, health monitoring, and personalized medicine. Its layer-by-layer fabrication approach enables the precise integration of functional materials and the tailored sensor architecture at micro and nano scales, which is crucial for next-generation biomedical applications. This review explores recent advancements in AM techniques for sensor fabrication, integration of nanomaterials, and their diverse biomedical applications. Various AM techniques such as stereolithography, selective laser sintering, and direct ink writing are discussed, highlighting their capabilities in producing intricate sensor structures. The paper discusses various fabrication methods, highlights nanomaterial integration strategies, and examines the biomedical applications of these sensors. Overall, it provides insights into the state-of-the-art in AM for micro and nanosensors, with implications for future developments in this field.

Three-dimensional material microstructuring by femtosecond laser-induced two-photon polymerization is emerging as an important tool in biomedicine. During two-photon polymerization, a tightly focused femtosecond laser pulse induces a crosslinking photoreaction in the polymer confined within the focal volume. As a rapid-prototyping technique, two-photon polymerization enables the fabrication of truly arbitrary three-dimensional micro- and nano-structures directly from computer models, with a spatial resolution down to 100 nm. In this review, we discuss the fundamentals, experimental methods, and materials used for two-photon polymerization; in addition, we present some applications of this technology related to microfluidics and to biomaterial scaffolds for tissue engineering and regenerative medicine.

Additive micro-manufacturing of crack-free PDCs by two-photon polymerization of a single, low-shrinkage preceramic resin

A material odyssey for 3D nano/microstructures: two photon polymerization based nanolithography in bioapplications

Stents are medical devices used to treat the narrowing of the blood vessel, most commonly caused by atherosclerosis. Currently used bare-metal, drug-eluting stents are limited in size and architectural complexity, and there are a few risks associated with these medical devices. In some cases stents can cause thrombosis or even death. Furthermore, said risk increases while stenting relatively small vessels. This paper shows that vascular stents for relatively small vessels and/or for patient-specific stenting applications can be printed using two-photon polymerization (2PP). 2PP is an additive manufacturing technique with sub-m resolution and unlimited 3D geometry potential. These capabilities were used to produce stents for small blood vessels, which are 5 mm tall and 0.7 or 0.9 mm in diameter, with 3D struts as thin as 50 m. Several novel approaches were introduced to accommodate the printing of such a structure like voxel elongation and printing in stereolithography-like vat-sample holder configuration. Furthermore, the produced stents were tested mechanically proving their mechanical resilience to most common types of mechanical deformations. Experimental results were also compared to mathematical modeling, showing excellent agreement, hinting at the possibility of designing and testing complex micro-stent geometries before fabrication in silico. Finally, biocompatibility experiments were performed, in which rats survived the 7-day incubation period and showed no significant biocompatibility issues. Overall, the presented work gives an outlook on all aspects related to the 3D printing of stents - design, manufacturing, mechanical, and biological testing. We show that 2PP aligns very well with all these aspects and is a promising technique for the mass manufacturing of vascular stents for small vessels or specifically for the patient.

Two-photon polymerized poly(caprolactone) retinal cell delivery scaffolds and their systemic and retinal biocompatibility

This review paper delves into the manufacturing methods, material properties, and applications of polymer‐based composites in the field of advanced manufacturing, offering a detailed explanation of their production through various additive manufacturing (AM) techniques and their diverse applications across multiple industries. Polymer‐based composite materials have emerged as crucial elements in AM due to their enhanced properties and design versatility, enabling the creation of components with unprecedented performance characteristics. The paper comprehensively covers the major AM methods employed for composite materials, including fused filament fabrication, Digital Light Processing/Stereolithography, Direct Ink Writing, and Selective Laser Sintering. Each of these methods is explored in terms of its mechanism, suitability for different composite materials, and the resulting material properties. The review also provides an insightful analysis of how these AM techniques are revolutionizing industries such as soft robotics, mechanical, electrical, and biomedical fields. The paper concludes by discussing the current challenges in this domain and projecting future trends in the development and application of composite materials in advanced manufacturing. This review aims to offer a comprehensive resource for researchers and practitioners in the field, highlighting the transformative impact of polymer‐based composites in AM and their growing significance across various sectors.Highlights Comprehensive review and classification of novelties in printing method for polymer based composite material manufacturing. Introduces innovative techniques to create and enhance material properties of composites. Explores interdisciplinary applications in biomedical, electronics, and sensors, demonstrating material versatility. Provides a systematic correlation between manufacturing method, material properties, and applications of novel polymer‐based composites.

4 - Biofabrication via integrated additive manufacturing and electrofluidodynamics

Schwarz P unit cell-based tissue scaffolds comprised of poly(D,L-lactide-co- ε -caprolactone)(PLCL) fabricated via the additive manufacturing technique, two-photon polymerisation (2PP) were found to undergo geometrical transformations from the original input design. A Schwarz P unit cell surface geometry CAD model was reconstructed to take into account the geometrical transformations through CAD modeling techniques using measurements obtained from an image-based averaging technique before its implementation for micromechanical analysis. Effective modulus results obtained from computational mechanical characterization via micromechanical analysis of the reconstructed unit cell assigned with the same material model making up the fabricated scaffolds demonstrated excellent agreement with a small margin of error at 6.94% from the experimental mean modulus (0.69 ± 0.29 MPa). The possible sources for the occurrence of geometrical transformations are discussed in this paper. The inter-relationships between different dimensional parameters making up the Schwarz P architecture and resulting effective modulus are also assessed and discussed. With the ability to accommodate the geometrical transformations, maintain efficiency in terms of time and computational resources, micromechanical analysis has the potential to be implemented in tissue scaffolds with a periodic microstructure as well as other structures outside the field of tissue engineering in general.

The ability to create complex three-dimensional microstructures has reached an unprecedented level of sophistication in the last 15 years. For the most part, this is the result of a steady development of the additive manufacturing technique named two-photon polymerization (TPP). In a short amount of time, TPP has gone from being a microfabrication novelty employed largely by laser specialists to a useful tool in the hands of scientists and engineers working in a wide range of research fields including microfluidics. When used in combination with traditional microfabrication processes, TPP can be employed to add unique three-dimensional components to planar platforms, thus enabling the realization of lab-on-a-chip solutions otherwise impossible to create. To take full advantage of TPP, an in-depth understanding is required of the materials photochemistry and the fabricated microstructures’ mechanical and chemical properties. Thus, we review methods developed so far to investigate the underling mechanism involved during TPP and analytical methods employed to characterize TPP microstructures. Furthermore, we will discuss potential opportunities for using optofluidics and lab-on-a-chip systems for TPP metrology.

The needs for high-resolution, well-defined and complex 3D microstructures in diverse fields call for the rapid development of novel 3D microfabrication techniques. Among those, two-photon polymerization (TPP) attracted extensive attention owing to its unique and useful characteristics. As an approach to implementing additive manufacturing, TPP has truly 3D writing ability to fabricate artificially designed constructs with arbitrary geometry. The spatial resolution of the manufactured structures via TPP can exceed the diffraction limit. The 3D structures fabricated by TPP could properly mimic the microenvironment of natural extracellular matrix, providing powerful tools for the study of cell behavior. TPP can meet the requirements of manufacturing technique for 3D scaffolds (engineering cell culture matrices) used in cytobiology, tissue engineering and regenerative medicine. In this review, we demonstrated the development in 3D microfabrication techniques and we presented an overview of the applications of TPP as an advanced manufacturing technique in complex 3D biomedical scaffolds fabrication. Given this multidisciplinary field, we discussed the perspectives of physics, materials science, chemistry, biomedicine and mechanical engineering. Additionally, we dived into the principles of tow-photon absorption (TPA) and TPP, requirements of 3D biomedical scaffolders, developed-to-date materials and chemical approaches used by TPP and manufacturing strategies based on mechanical engineering. In the end, we draw out the limitations of TPP on 3D manufacturing for now along with some prospects of its future outlook towards the fabrication of 3D biomedical scaffolds.

Compared with conventional microfabrication techniques, two-photon polymerization has attracted significant interest due to its capability of building arbitrary, complex and ultraprecise three-dimensional (3D) microstructures with sub-100 nm resolution. The process exploits femtosecond laser pulses and a photo resist that is transparent at the laser wavelength (515 nm) but absorbs two photons at high intensity to polymerize, resulting in the possibility of fabricating devices for advanced photonics and biomedical applications. In this paper, the manufacturing of 3D microstructures through two-photon polymerization is discussed.