Fluid bath-assisted three-dimensional (3D) printing is an innovative 3D printing strategy that extrudes liquid ink materials into a fluid bath to form various 3D configurations. Since the support bath can provide in situ support, extruded filaments are able to freely construct complex 3D structures. Meanwhile, the supporting function of the fluid bath decreases the dependence of the ink material's cross-linkability, thus broadening the material selections for biomedical applications. Fluid bath-assisted 3D printing can be divided into two subcategories: embedded 3D printing and support bath-enabled 3D printing. This review will introduce and discuss three main manufacturing processes, or stages, for these two strategies. The stages that will be discussed include preprinting, printing, and postprinting. In the preprinting stage, representative fluid bath materials are introduced and the bath material preparation methods are also discussed. In addition, the design criteria of fluid bath materials including biocompatibility, rheological properties, physical/chemical stability, hydrophilicity/hydrophobicity, and other properties are proposed in order to guide the selection and design of future fluid bath materials. For the printing stage, some key technical issues discussed in this review include filament formation mechanisms in a fluid bath, effects of nozzle movement on printed structures, and design strategies for printing paths. In the postprinting stage, some commonly used postprinting processes are introduced. Finally, representative biomedical applications of fluid bath-assisted 3D printing, such as standalone organoids/tissues, biomedical microfluidic devices, and wearable and bionic devices, are summarized and presented.
Yield-stress support bath-enabled three-dimensional (3D)
printing
has been widely used in recent years for diverse applications. However,
current yield-stress fluids usually possess single microstructures
and still face the challenges of on-demand adding and/or removing
support bath materials during printing, constraining their application
scope. This study aims to propose a concept of stimuli-responsive
yield-stress fluids with an interactive dual microstructure as support
bath materials. The microstructure from a yield-stress additive allows
the fluids to present switchable states at different stresses, facilitating
an embedded 3D printing process. The microstructure from stimuli-responsive
polymers enables the fluids to have regulable rheological properties
upon external stimuli, making it feasible to perfuse additional yield-stress
fluids during printing and easily remove residual fluids after printing.
A nanoclay-Pluronic F127 nanocomposite is studied as a thermosensitive
yield-stress fluid. The key material properties are characterized
to unveil the interactions in the formed dual microstructure and microstructure
evolutions at different stresses and temperatures. Core scientific
issues, including the filament formation principle, surface roughness
control, and thermal effects of the newly added nanocomposite, are
comprehensively investigated. Finally, three representative 3D structures,
the Hall of Prayer, capsule, and tube with changing diameter, are
successfully printed to validate the printing capability of stimuli-responsive
yield-stress fluids for fabricating arbitrary architectures.
Pediatric orbital trapdoor fractures are common in children and adolescents and usually require emergency surgical intervention. Herein, a personalized 3D printing-assisted approach to surgical treatment is proposed, serving to accurately and effectively repair pediatric orbital trapdoor fractures. We first investigated stress distribution in external force-induced orbital blowout fractures via numerical simulation, determining that maximum stresses on inferior and medial walls exceed those on superior and lateral walls and thus confer higher probability of fracture. We also examined 36 pediatric patients treated for orbital trapdoor fractures between 2014 and 2019 to verify our theoretical construct. Using 3D printing technique, we then created orbital models based on computed tomography (CT) studies of these patients. Absorbable implants were tailor-made, replicating those of 3D-printed models during surgical repairs of fractured orbital bones. As follow-up, we compared CT images and clinical parameters (extraocular movements, diplopia, enophthalmos) before and 12 months after operative procedures. There were only two patients with diplopia and six with enophthalmos >2 mm at 12 months, attesting to the efficacy of our novel 3D printing-assisted strategy.
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