Bioprinting has emerged as a strong tool for devising regenerative therapies to address unmet medical needs. However, the translation of conventional in vitro bioprinting approaches is partially ...hindered due to challenges associated with the fabrication and implantation of irregularly shaped scaffolds and their limited accessibility for immediate treatment by healthcare providers. An alternative strategy that has recently drawn significant attention is to directly print the bioink into the patient’s body, so-called ‘in situ bioprinting’. The bioprinting strategy and the associated bioink need to be specifically designed for in situ bioprinting to meet the particular requirements of direct deposition in vivo. In this review, we discuss the developed in situ bioprinting strategies, their advantages, challenges, and possible future improvements.
Bioprinting has emerged a strong tool for engineering of complex tissues; however, its clinical translation has been challenging due to unreliable fabrication and implantation scaffolds and its limited accessibility.In situ bioprinting, direct bioprinting inside the defect, has been introduced as an alternative strategy for translation of bioprinting from bench to bedside.Different automatic and handheld in situ bioprinting strategies have been developed to realize in vivo printing inside a patient’s body.Both automated and handheld bioprinting strategies have their own benefits and challenges, which should be addressed before their clinical application.The integration of human intelligence and accuracy of robotic systems through the development of robotic-assisted bioprinting could be a future trend in the bioprinting field for regenerative applications.
Volumetric muscle loss (VML), which refers to a composite skeletal muscle defect, most commonly heals by scarring and minimal muscle regeneration but substantial fibrosis. Current surgical ...interventions and physical therapy techniques are limited in restoring muscle function following VML. Novel tissue engineering strategies may offer an option to promote functional muscle recovery. The present study evaluates a colloidal scaffold with hierarchical porosity and controlled mechanical properties for the treatment of VML. In addition, as VML results in an acute decrease in insulin-like growth factor 1 (IGF-1), a myogenic factor, the scaffold was designed to slowly release IGF-1 following implantation. The foam-like scaffold is directly crosslinked onto remnant muscle without the need for suturing. In situ 3D printing of IGF-1-releasing porous muscle scaffold onto VML injuries resulted in robust tissue ingrowth, improved muscle repair, and increased muscle strength in a murine VML model. Histological analysis confirmed regeneration of new muscle in the engineered scaffolds. In addition, the scaffolds significantly reduced fibrosis and increased the expression of neuromuscular junctions in the newly regenerated tissue. Exercise training, when combined with the engineered scaffolds, augmented the treatment outcome in a synergistic fashion. These data suggest highly porous scaffolds and exercise therapy, in combination, may be a treatment option following VML.
Reconstructive surgery remains inadequate for the treatment of volumetric muscle loss (VML). The geometry of skeletal muscle defects in VML injuries varies on a case-by-case basis. Three-dimensional ...(3D) printing has emerged as one strategy that enables the fabrication of scaffolds that match the geometry of the defect site. However, the time and facilities needed for imaging the defect site, processing to render computer models, and printing a suitable scaffold prevent immediate reconstructive interventions post-traumatic injuries. In addition, the proper implantation of hydrogel-based scaffolds, which have generated promising results in vitro, is a major challenge. To overcome these challenges, a paradigm is proposed in which gelatin-based hydrogels are printed directly into the defect area and cross-linked in situ. The adhesiveness of the bioink hydrogel to the skeletal muscles was assessed ex vivo. The suitability of the in situ printed bioink for the delivery of cells is successfully assessed in vitro. Acellular scaffolds are directly printed into the defect site of mice with VML injury, exhibiting proper adhesion to the surrounding tissue and promoting remnant skeletal muscle hypertrophy. The developed handheld printer capable of 3D in situ printing of adhesive scaffolds is a paradigm shift in the rapid yet precise filling of complex skeletal muscle tissue defects.
bioprinting-the process of depositing bioinks at a defected area, has recently emerged as a versatile technology for tissue repair and restoration
site-specific delivery of pro-healing constructs. ...The ability to print multiple materials
is an exciting approach that allows simultaneous or sequential dispensing of different materials and cells to achieve tissue biomimicry. Herein, we report a modular handheld bioprinter that deposits a variety of bioinks
with exquisite control over their physical and chemical properties. Combined stereolithography 3D printing and microfluidic technologies allowed us to develop a novel low-priced handheld bioprinter. The ergonomic design of the handheld bioprinter facilitate the shape-controlled biofabrication of multi-component fibers with different cross-sectional shapes and material compositions. Furthermore, the capabilities of the produced fibers in the local delivery of therapeutic agents was demonstrated by incorporating drug-loaded microcarriers, extending the application of the printed fibers to on-demand, temporal, and dosage-control drug delivery platforms. Also, the versatility of this platform to produce biosensors and wearable electronics was demonstrated via incorporating conductive materials and integrating pH-responsive dyes. The handheld printer's efficacy in generating cell-laden fibers with high cell viability for site-specific cell delivery was shown by producing single-component and multi-component cell-laden fibers. In particular, the multi-component fibers were able to model the invasion of cancer cells into the adjacent tissue.
In situ printing gives insight into the evolution of morphology and optical properties during slot-die coating of active layers for application in organic solar cells and enables an upscaling and ...optimization of the thin film deposition process and the photovoltaic performance. Active layers based on the conjugated polymer donor with benzodithiophene units PBDB-T-2Cl and the non-fullerene small-molecule acceptor IT-4F are printed with a slot-die coating technique and probed in situ with grazing incidence small-angle X-ray scattering, grazing incidence wide-angle X-ray scattering, and ultraviolet/visible light spectroscopy. The formation of the morphology is followed from the liquid state to the final dry film for different printing conditions (at 25 and 35 °C), and five regimes of film formation are determined. The morphological changes are correlated to changing optical properties. During the film formation, crystallization of the non-fullerene small-molecule acceptor takes place and polymer domains with sizes of some tens of nanometers emerge. A red shift of the optical band gap and a broadening of the absorbance spectrum occurs, which allow for exploiting the sun spectrum more efficiently and are expected to have a favorable effect on the solar cell performance.
In the construction industry, the labor shortage is a global issue. Characterized by the forming process of layered extrusion and rapid solidification, 3D concrete printing (3DCP) technology begins ...to be used in digital concrete construction to minimize the demand for manpower. However, the utilization of 3DCP in full-scale architectural constructions is still in its infancy, involving many manual processes like rebars-binding and formwork-making, which reduces the benefits of construction automation that should be brought by such technology. Therefore, this study proposes a design-to-printing workflow to 3D print the entire structure of a farmhouse in Wujiazhuang (WJZ) village. Firstly, design strategies are built up by a series of multi-disciplinary research, including printing system development, site planning, material design, and structure evaluation. Secondly, construction strategies involving printing process organization and man-hour-saving construction methods are utilized in the 3D printing process. By applying the introduced workflow, the project saves 62.4 % of human resources compared with the traditional reinforced concrete (RC) method, and the participation of 3D printing technologies arises from 18.3 % in the common 3DCP scenario to 76.5 % in this project. The on-site construction duration of the WJZ farmhouse is also reduced by 24.5 % in comparison with the unplanned construction process.
•The paper introduces a mobile robotic 3D concrete printing system for in-situ construction.•An organized design-to-printing workflow is applied in a housing project located in a remote mountain village.•The sulpho-aluminous cement is adopted as printing inks to build the entire structure of the house.•Practical construction methods are utilized to simplify manual procedures and solve problems brought by the compact site.•The proposed workflow effectually saves both human resources and on-site construction duration.
Printing of active layers for high‐efficiency organic solar cells with the slot‐die coating technique can overcome the challenge of upscaling, which will be needed for organic photovoltaics on its ...way to marketability. The morphology of a bulk‐heterojunction organic solar cell has a very high impact on its power conversion efficiency. Therefore, it is of particular importance to understand the mechanisms of structure formation during printing of active layers to enable further optimization of the solar cell performance and upscaling of the production process. Meniscus‐guided slot‐die coating of the blend of a low bandgap conjugated polymer donor with benzodithiophene units PBDB‐T‐SF and the nonfullerene small molecule acceptor IT‐4F is studied in situ with optical microscopy, Ultraviolet–visible spectroscopy, and grazing incidence small angle X‐ray scattering. The structure formation is followed from the liquid to the final dry film state. Thereby, five regimes of morphology formation are determined. The morphological evolution in the printed active layer is correlated to changing optical properties of the thin film. In the final dry film, polymer domains of several tens of nanometers are observed, which will be favorable for application in high‐efficiency organic solar cells.
Meniscus‐guided slot‐die coating of the blend of a low bandgap conjugated polymer donor with benzodithiophene units PBDB‐T‐SF and the nonfullerene small molecule acceptor IT‐4F is studied in situ using optical microscopy, UV–vis spectroscopy, and grazing incidence small angle X‐ray scattering. The structure formation is followed from the liquid to the final dry film state.
Traditional tissue engineering methods face challenges, such as fabrication, implantation of irregularly shaped scaffolds, and limited accessibility for immediate healthcare providers. In situ ...bioprinting, an alternate strategy, involves direct deposition of biomaterials, cells, and bioactive factors at the site, facilitating on-site fabrication of intricate tissue, which can offer a patient-specific personalized approach and align with the principles of precision medicine. It can be applied using a handled device and robotic arms to various tissues, including skin, bone, cartilage, muscle, and composite tissues. Bioinks, the critical components of bioprinting that support cell viability and tissue development, play a crucial role in the success of in situ bioprinting. This review discusses in situ bioprinting techniques, the materials used for bioinks, and their critical properties for successful applications. Finally, we discuss the challenges and future trends in accelerating in situ printing to translate this technology in a clinical settings for personalized regenerative medicine.
Among various printing technologies for fabrication of electronic devices, microplotter printing and inkjet printing provide the best printing resolution. For inkjet printing, which is compatible ...with only low-viscosity inks, the “coffee ring effect” and time-/labor-consuming nonprinting operations are among the most that impose challenges to its applications for rapid and large-scale fabrication of electronic devices. When printing a flexible electronic device that tends to bend spontaneously, relocating an unfinished/undried workpiece for post-printing treatments usually causes ink diffusion, resulting in deteriorated printing resolution, nonuniformity, and defects. Taking the printing of a poly(vinylidene fluoride)- (PVDF-) based flexible nanogenerator as an example, this work utilized a high-viscosity compatible microplotter printer and a concentrated/viscous PVDF ink (which minimized the “coffee ring effect)” and an in situ fabrication process (which not only maximally facilitated and minimized the nonprinting operations but also avoided the deterioration of the printing resolution and the nonuniformity/defects). A morphological comparison investigation showed that a PVDF patch printed (for only two passes with a concentrated 7 wt % PVDF ink) with a microplotter was morphologically homogeneous with no observable defects, while a PVDF patch printed (for 80 passes with a diluted 0.5 wt % PVDF ink) with a typical inkjet printer exhibited conspicuous nonuniformity and defects like grooves, pits, and cracks. Performance characterization of such a nanogenerator showed that it generated negative–positive twin pulses of short-circuit current during its cyclic bending and unbending, with a short-circuit current density magnitude up to ∼0.4 μA/cm2. A flexible carbon nanotube-based chemiresistive gas sensor was also fully printed in situ, in order to demonstrate that the in situ printing method utilized in this work is also compatible with fine features and low-viscosity inks.
Purpose
Path planning is an important part of three-dimensional (3D) printing data processing technology. This study aims to propose a new path planning method based on a discontinuous grid partition ...algorithm of point cloud for in situ printing.
Design/methodology/approach
Three types of parameters (i.e. structural, process and path interruption parameters) were designed to establish the algorithm model with the path error and the computation amount as the dependent variables. The path error (i.e. boundary error and internal error) was further studied and the influence of each parameter on the path point density was analyzed quantitatively. The feasibility of this method was verified by skin in situ printing experiments.
Findings
Path point density was positively correlated with Grid_size and negatively related to other parameters. Point_space, Sparsity and Line_space had greater influence on path point density than Indentation and Grid_size. In skin in situ printing experiment, two layers of orthogonal printing path were generated, and the material was printed accurately in the defect, which proved the feasibility of this method.
Originality/value
This study proposed a new path planning method that converted 3D point cloud data to a printing path directly, providing a new path planning solution for in situ printing. The discontinuous grid partition algorithm achieved controllability of the path planning accuracy and computation amount that could be applied to different processes.
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