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Over the years, the field of bioprinting has attracted attention for its highly automated 16 fabrication system that enables the precise patterning of living cells and biomaterials at pre-17 defined positions for enhanced cell-matrix and cell-cell interactions. Notably, vat polymerization 18 (VP)-based bioprinting is an emerging bioprinting technique for various tissue engineering 19 applications due to its high fabrication accuracy. Particularly, different photo-initiators (PIs) are 20 utilized during the bioprinting process to facilitate the crosslinking mechanism for fabrication of 21 high-resolution complex tissue constructs. The advancements in VP-based printing have led to a 22 paradigm shift in fabrication of tissue constructs from cell-seeding of tissue scaffolds (non-23 biocompatible fabrication process) to direct bioprinting of cell-laden tissue constructs 24 (biocompatible fabrication process). This paper, presenting a first-time comprehensive review of 25 the VP-based bioprinting process, provides an in-depth analysis and comparison of the various 26 biocompatible PIs and highlights the important considerations and bioprinting requirements. This 27 review paper reports a detailed analysis of its printing process and the influence of light-based 28 curing modality and PIs on living cells. Lastly, this review also highlights the significance of VP-29 based bioprinting, the regulatory challenges and presents future directions to transform the VP-30 Page 1 of 47 AUTHOR SUBMITTED MANUSCRIPT -BF-102156.R2based printing technology into imperative tools in the field of tissue engineering and regenerative 31 medicine. The readers will be informed on the current limitations and achievements of the VP-32 based bioprinting techniques. Notably, the readers will realize the importance and value of 33 highly-automated platforms for tissue engineering applications and be able to develop objective 34 viewpoints towards this field.

Additive manufacturing (AM) has brought about a revolution in the way we can manufacture complex products with customized features. AM has paved its way in the application areas ranging from aerospace, automotive, consumer to biomedical. AM of composites has attracted special attention due to its promise in improving, modifying, and diversifying the properties of generic materials through introducing reinforcements. This review provides a detailed landscape of fiber‐reinforced composites processed via AM techniques. Different AM processes, various material formulations, and strengths and drawbacks of AM methods are discussed. Emphasis is paid to AM techniques focusing on continuous fibers, as they hold the promise of becoming the next‐generation composite fabrication methodology. The article also tries to identify the potential of AM technology for fiber‐reinforced composites and delves into challenges facing the area.

Bioprinting is a promising automated platform that enables the simultaneous deposition of multiple types of cells and biomaterials to fabricate complex three-dimensional (3D) tissue constructs. Collagen-based biomaterial used in most of the previous works on skin bioprinting has poor printability and long crosslinking time. This posed an immense challenge to create 3D constructs with pre-determined shape and configuration at high throughput. Recently, the use of chitosan for wound healing applications has attracted huge attention due to its attractive traits such as its antimicrobial properties and ability to trigger hemostasis. In this paper, we optimized polyelectrolyte gelatin-chitosan hydrogel for 3D bioprinting. Modification to the chitosan was carried out via the oppositely charged functional groups from chitosan and gelatin at a specific pH of ~pH 6.5 to form polyelectrolyte complexes. The polyelectrolyte hydrogels were evaluated in terms of physical interactions within polymer blend, rheological properties (viscosities, storage and loss modulus), printing resolution at varying pressures and feed rates and biocompatibility. The polyelectrolyte gelatin-chitosan hydrogels formulated in this work was optimized for 3D bioprinting at room temperature to achieve high shape fidelity of the printed 3D constructs and good biocompatibility with fibroblast skin cells.

This article provides a database of the mechanical properties of additively manufactured polymeric materials fabricated using material extrusion (e.g., fused filament fabrication (FFF)).Mechanical properties available in the literatures are consolidated in table form for different polymeric materials for FFF. Mechanical properties such as tensile, compressive, flexural, fatigue and creep properties are discussed in detail. The effects of printing parameters such as raster angle, infill, and specimen orientation on properties are also provided, together with a discussion of the possible causes (e.g., texture, microstructure changes, and defects) of anisotropy in properties. In addition to that, research gaps are identified which warrant further investigation.

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Flexible and stretchable strain sensors are in great demand for many applications like wearables and home health. This work reports a strain sensor fabricated using aerosol jet printing technology on a commercially available bandage to be used as a low-cost wearable. Laser light is explored to sinter the silver nanoparticle ink on low-temperature bandage substrate. The laser parameters, their effects on the microstructure of the film, and the resulting sensor performance are systematically investigated. The results showed that the sensor is stretchable, has good sensitivity, and stability for 700 cycles of repeated bending.

Hydrogels are 3D networks that have a high water content. They have been widely used as cell carriers and scaffolds in tissue engineering due to their structural similarities to the natural extracellular matrix. Among these, "Smart" hydrogels refer to a group of hydrogels that is responsive to various external stimuli such as pH, temperature, light, electric, and magnetic field. Combining the potential of 3D printing and smart hydrogels is an exciting new paradigm in the fabrication of a functional 3D tissue. In this article, we provide a state-of-the-art review on smart hydrogels and bioprinting. We identify the critical material properties needed for the most commonly used bioprinting techniques, namely extrusion-based, inkjet-based, and laser-based techniques. The latest progress in different smart hydrogel systems and their applications in bioprinting are presented. The challenges of printing these hydrogel systems are also highlighted. Lastly, we present the potentials and the future perspectives of smart hydrogels in 3D bioprinting.