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Curl distortion has been a persistent challenge for vat photopolymerization‐based printing technology such as digital light processing (DLP), leading to structural deformation and print failures. This study presents a new approach to mitigate curling distortion and heat effects during DLP printing by dividing the printing layer image into sequential subimages, using a breadth‐first search algorithm. The progressive curing process, resembling a ripple pattern, results in a significant improvement in printing accuracy. The deviation is reduced tenfold when the layer image is divided into subimages with 10 pixels for a 32 mm diameter disc. Additionally, subdivision strategy helps to reduce the heat effect during photopolymerization, as monitored in situ by a long‐wave infrared camera. The successful reduction of residual stress using the subdivision strategy results in a 75% improvement in the mechanical performance of the printed products. The simple adoption of subdivision strategy in practical 3D printing applications is also demonstrated. For solid 3D printing structures, introducing intervals within the solid printing layers—such as using a grid structure instead of a fully solid one, can help to reduce curling and heat effects, thereby improving 3D printing accuracy. [ABSTRACT FROM AUTHOR] more...

Hydrogel 3D printing holds immense potential in fields like personalized medicine, regenerative therapies, and organ creation, offering biocompatible structures similar to the extracellular matrix. Gelatin‐Methacryloyl (GelMA) emerges as a promising candidate, while its high viscosity poses a significant challenge, especially in vat photopolymerization‐based 3D printing. Here, a new approach is presented by using Hofmeister ionic effect to substantially reduce the viscosity of high‐content (up to 60%) Gelatin bioink at room temperature with enhanced mechanical performance of the printed structures. The thinning effect induced by chaotropic Hofmeister ions is investigated through complex viscosity analysis, optical rotation measurements, and sol–gel conversion studies. The thinning effect induced by chaotropic ions enables precise 3D printing of Gelatin hydrogel, achieving accuracy comparable to prints made with polymers. Furthermore, after polymerization, the cations of the chaotropic salt change their role to cross‐linkers, leading to stronger scaffolds that exhibit biocompatibility with robust cell attachment, proliferation, and suitability for cell growth. The combination facilitates the creation of customizable structures and high printing accuracy will promote the wide application of Gelatin in the development of patient‐specific implants, drug delivery systems, and tissue scaffolds, further improving medical treatment efficacy and personalized healthcare. [ABSTRACT FROM AUTHOR] more...

Hydrogels have revolutionized the field of soft robotics with their ability to provide dynamic and programmable responses to different stimuli, enabling the fabrication of highly adaptable and flexible robots. This continual development holds significant promise for applications in biomedical devices, active implants, and sensors due to the biocompatibility of hydrogels. Actuation in hydrogel-based soft robotics relies on variations in material properties, structural design, or a combination of both to generate desired movements and behaviors. While such traditional approaches enable hydrogel actuation, they often rely on complex material design, bringing challenges to hydrogel fabrication and hindering practical use. Therefore, this work seeks to present a simplified and versatile approach for fabricating programmable single-component hydrogel-based soft robotics using an encoded building block design concept and 3D printing. A series of structural building blocks have been designed to achieve various actuation characteristics, including the direction, degree, and kinetics of actuation. By assembling these building blocks into various configurations, a broader range of actuation responses can be encoded, allowing for the fabrication of versatile, programmable soft robotics using a single uniform material through vat photopolymerization 3D printing. This approach enables adaptation to a wide range of applications, providing highly customizable encoding designs. [ABSTRACT FROM AUTHOR] more...

Vat photopolymerization (VPP) based three‐dimensional (3D) printing, including stereolithography (SLA) and digital light projection (DLP), is known for producing intricate, high‐precision prototypes with superior mechanical properties. However, the challenge lies in the non‐recyclability of covalently crosslinked thermosets used in these printing processes, limiting the sustainable utilization of printed prototypes. This review paper examines the recently explored avenue of VPP 3D‐printed dynamic covalent network (DCN) polymers, which enable reversible crosslinks and allow for the reprocessing of printed prototypes, promoting sustainability. These reversible crosslinks facilitate the rearrangement of crosslinked polymers, providing printed polymers with chemical/physical recyclability, self‐healing capabilities, and degradability. While various mechanisms for DCN polymer systems are explored, this paper focuses solely on photocurable polymers to highlight their potential to revolutionize the sustainability of VPP 3D printing. [ABSTRACT FROM AUTHOR] more...

The flexibility and controllability of 3D printing technologies have made them popular for creating integrated wearable sensors. However, producing sensors with 3D anisotropic response is still difficult with current printing materials and techniques. To address this challenge, digital light process (DLP) printing technology with blading function to fabricate 3D anisotropic pressure and strain sensors is used. By applying blading‐induced shearing force, nanoalignment of carbon nanotubes (CNTs) in each layer is achieved, while the continuous liquid interface production of the DLP printing process facilitates good electrical communication between adjacent microlayers. The constructed 3D sensor displays high tensile and pressure responses up to 40 MPa and the ability to detect pressure changes in all directions. Additionally, the resistance anisotropy ratio range is adjustable. Finite‐element method (FEM) simulation shows that the relative change in resistance has an anisotropic distribution that aligns well with experimental results. The work would offer a new way to create 3D anisotropic pressure/strain sensors for advanced flexible and stretchable sensing applications. [ABSTRACT FROM AUTHOR] more...

Materials with negative Poisson's ratio have attracted considerable attention and offered high potential applications as biomedical devices due to their ability to expand in every direction when stretched. Although negative Poisson's ratio has been obtained in various base materials such as metals and polymers, there are very limited works on hydrogels due to their intrinsic brittleness. Herein, we report the use of methacrylated cellulose nanocrystals (CNCMAs) as a macro‐cross‐linking agent in poly(2‐hydroxyethyl methacrylate) (pHEMA) hydrogels for 3D printing of auxetic structures. Our developed CNCMA‐pHEMA hydrogels exhibit significant improvements in mechanical properties, which is attributed to the coexistence of multiple chemical and physical interactions between the pHEMA and CNCMAs. Structures printed by using CNCMA‐pHEMA hydrogels show auxetic behavior with greatly enhanced toughness and stretchability compared to the hydrogel with a traditional cross‐linking agent. Such strong and tough auxetic hydrogels would contribute toward establishing advanced flexible implantable devices such as biodegradable oesophageal self‐expandable stents. [ABSTRACT FROM AUTHOR] more...

One‐dimensional fillers such as rods and fibers have shown effective mechanical reinforcement in polymer nanocomposites, but their application in vat polymerization‐based 3D printing techniques was hindered due to the rapidly increased viscosity of the resin. In order to improve the fluidity of the composites without sacrificing the mechanical performance, herein we demonstrated that one‐dimensional hydroxyapatite (HAP) whiskers could be surface modified with 3‐(trimethoxysilyl) propyl methacrylate, to decrease the viscosity of the resulting resins and to enhance the interfacial adhesion between the filler and matrix. Rheology results showed that the resin was still fluidic with loading of HAP whiskers up to 20 wt%, with Young's modulus increased by a factor of 98% and the ultimate tensile strength increased by 26%. Successful printing of the resin on a DLP printer was achieved with high resolution and fine surface, and the biocompatibility test showed an increase in cell viability with the addition of HAP whiskers. These results provide a promising approach to develop high‐performance printable resin for orthopedic and related bio‐printing. [ABSTRACT FROM AUTHOR] more...

The development of additive manufacturing has offered great potential as well as challenge to resins with good performance. Here we report a facile strategy to obtain significant enhancement of mechanical properties for resins via incorporation of boehmite nanowires surface modified by a new modifier β -carboxyethyl acrylate ( β -CEA), instead of the commonly used coupling agent 3-trimethoxysilylpropyl methacrylate (TMSPM). Fourier Transform Infrared Spectroscopy (FT-IR) and thermogravimetric analysis (TGA) characterizations were conducted to demonstrate the grafting of β -CEA onto the surface of boehmite nanowires. Significant mechanical enhancement was demonstrated by manufacturing and evaluation of product quality of delicate Fullerene model with neat acrylate and composite resins with β -CEA-AlOOH via Digital Light Processing (DLP) 3D printing. [ABSTRACT FROM AUTHOR] more...

ABSTRACT Liquid resins-based three-dimensional (3D) printing techniques such as stereolithography and digital light processing (DLP) show higher resolution and accuracy than other printing techniques, but their applications have been impeded by the limited materials selection and lack of functions. We here reported the preparation of luminescent resins for DLP-based 3D printing. Homogeneous dispersion of the fluorescent dyes was achieved by small acrylate molecules screening, and the cure depth studies was used to optimize both resin composition and printing parameters setting. In addition, we showed that the optical analysis of absorption and emission spectra is an important tool to reduce the complex mutual-interference of the light absorption of dye, photoinitiator and photo-absorber in the printable resin. We also developed the mater batch technique to tune the emitting colors in the whole visible range, together with white emitting. By using the developed resins, different 3D structures with different emitting colors were successfully printed by DLP technique. These results will further widen the applications of the liquid resins-based 3D printing techniques, and these luminescent resins show highly potential applications in education, lighting, UV converters, and so on. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44988. [ABSTRACT FROM AUTHOR] more...