Tuning the material properties of a water-soluble ionic polymer using different counterions for material extrusion additive manufacturing

Fused Deposition Modelling (FDM) of Thermoplastic-Based Filaments: Process and Rheological Properties-An Overview

The fused deposition modeling (FDM) process, an extrusion-based 3D printing technology, enables the manufacture of complex geometrical elements. This technology employs diverse materials, including thermoplastic polymers and composites as well as recycled resins to encourage sustainable growth. FDM is used in a variety of industrial fields, including automotive, biomedical, and textiles, as a rapid prototyping method to reduce costs and shorten production time, or to develop items with detailed designs and high precision. The main phases of this technology include the feeding of solid filament into a molten chamber, capillary flow of a non-Newtonian fluid through a nozzle, layer deposition on the support base, and layer-to-layer adhesion. The viscoelastic properties of processed materials are essential in each of the FDM steps: (i) predicting the printability of the melted material during FDM extrusion and ensuring a continuous flow across the nozzle; (ii) controlling the deposition process of the molten filament on the print bed and avoiding fast material leakage and loss of precision in the molded part; and (iii) ensuring layer adhesion in the subsequent consolidation phase. Regarding this framework, this work aimed to collect knowledge on FDM extrusion and on different types of rheological properties in order to forecast the performance of thermoplastics.

Mechanically promoted lipid-based filaments via composition tuning for extrusion-based 3D-printing

Lipid excipients are favorable materials in pharmaceutical formulations owing to their natural, biodegradable, low-toxic and solubility/permeability enhancing properties. The application of these materials with advanced manufacturing platforms, particularly filament-based 3D-printing, is attractive for personalized manufacturing of thermolabile drugs. However, the filament's weak mechanical properties limit their full potential. In this study, highly flexible filaments were extruded using PG6-C16P, a lipid-based excipient belonging to the group of polyglycerol esters of fatty acids (PGFAs), based on tuning the ratio between its major and minor composition fractions. Increasing the percentage of the minor fractions in the system was found to enhance the relevant mechanical filament properties by 50-fold, guaranteeing a flawless 3D-printability. Applying a novel liquid feeding approach further improved the mechanical filament properties at lower percentage of minor fractions, whilst circumventing the issues associated with the standard extrusion approach such as low throughput. Upon drug incorporation, the filaments retained high mechanical properties with a controlled drug release pattern. This work demonstrates PG6-C16 P as an advanced lipid-based material and a competitive printing excipient that can empower filament-based 3D-printing.

Role of Rheology in Morphology Development and Advanced Processing of Thermoplastic Polymer Materials: A Review

This review presents fundamental knowledge and recent advances pertaining to research on the role of rheology in polymer processing, highlights the knowledge gap between the function of rheology in various processing operations and the importance of rheology in the development, characterization, and assessment of the morphologies of polymeric materials, and offers ideas for enhancing the processabilities of polymeric materials in advanced processing operations. Rheology plays a crucial role in the morphological evolution of polymer blends and composites, influencing the type of morphology in the case of blends and the quality of dispersion in the cases of both blends and composites. The rheological characteristics of multiphase polymeric materials provide valuable information on the morphologies of these materials, thereby rendering rheology an important tool for morphological assessment. Although rheology extensively affects the processabilities of polymeric materials in all processing operations, this review focuses on the roles of rheology in film blowing, electrospinning, centrifugal jet spinning, and the three-dimensional printing of polymeric materials, which are advanced processing operations that have gained significant research interest. This review offers a comprehensive overview of the fundamentals of morphology development and the aforementioned processing techniques; moreover, it covers all vital aspects related to the tailoring of the rheological characteristics of polymeric materials for achieving superior morphologies and high processabilities of these materials in advanced processing operations. Thus, this article provides a direction for future advancements in polymer processing. Furthermore, the superiority of elongational flow over shear flow in enhancing the quality of dispersion in multiphase polymeric materials and the role of extensional rheology in the advanced processing operations of these materials, which have rarely been discussed in previous reviews, have been critically analyzed in this review. In summary, this article offers new insights into the use of rheology in material and product development during advanced polymer-processing operations.

Fused Deposition Modeling (FDM), the new asset for the production of tailored medicines

Over the last few years, conventional medicine has been increasingly moving towards precision medicine. Today, the production of oral pharmaceutical forms tailored to patients is not achievable by traditional industrial means. A promising solution to customize oral drug delivery has been found in the utilization of 3D Printing and in particular Fused Deposition Modeling (FDM). Thus, the aim of this systematic literature review is to provide a synthesis on the production of pharmaceutical solid oral forms using FDM technology. In total, 72 relevant articles have been identified via two well-known scientific databases (PubMed and ScienceDirect). Overall, three different FDM methods have been reported: "Impregnation-FDM", "Hot Melt Extrusion coupled with FDM" and "Print-fill", which yielded to the formulation of thermoplastic polymers used as main component, five families of other excipients playing different functional roles and 47 active ingredients. Solutions are underway to overcome the high printing temperatures, which was the initial brake on to use thermosensitive ingredients with this technology. Also, the moisture sensitivity shown by a large number of prints in preliminary storage studies is highlighted. FDM seems to be especially fitted for the treatment of rare diseases, and particular populations requiring tailored doses or release kinetics. For future use of FDM in clinical trials, an implication of health regulatory agencies would be necessary. Hence, further efforts would likely be oriented to the use of a quality approach such as "Quality by Design" which could facilitate its approval by the authorities, and also be an aid to the development of this technology for manufacturers.

Quadruple Hydrogen Bonding Supramolecular Elastomers for Melt Extrusion Additive Manufacturing

This manuscript describes the versatility of highly directional, noncovalent interactions, i.e., quadruple hydrogen bonding (QHB), to afford novel polyurea segmented supramolecular polymers for melt extrusion three-dimensional (3D) printing processes. The molecular design of the polyurea elastomers features (1) flexible polyether segments and relatively weak urea hydrogen-bonding sites in the soft segments to provide elasticity and toughness, and (2) strong ureido-cytosine (UCyt) QHB in the hard segments to impart enhanced mechanical integrity. The resulting polyureas were readily compression-molded into mechanically-robust, transparent, and creasable films. Optimization of polyurea composition offered a rare combination of high tensile strength (95 MPa), tensile elongation (788% strain), and toughness (94 MJ/m³), which are superior to a commercially available Ninjaflex elastomer. The incorporation of QHB facilitated melt processability, where hydrogen bonding dissociation provided low viscosities at printing temperatures. During cooling, directional self-assembly of UCyt QHB facilitated the solidification process and contributed to part fidelity with the formation of a robust physical network. The printed objects displayed high layer fidelity, smooth surfaces, minimal warpage, and complex geometries. The presence of highly directional QHB effectively diminished mechanical anisotropy, and the printed samples exhibited comparable Young's moduli along (x-y direction, 0°) and perpendicular to (z-direction, 90°) the layer direction. Remarkably, the printed samples exhibited ultimate tensile strains approaching 500% in the z-direction prior to failure, which was indicative of improved interlayer adhesion. Thus, this design paradigm, which is demonstrated for novel polyurea copolymers, suggests the potential of supramolecular polymers with enhanced mechanical performance, melt processability, recyclability, and improved interlayer adhesion for melt extrusion additive manufacturing processes.

100th Anniversary of Macromolecular Science Viewpoint: Macromolecular Materials for Additive Manufacturing

Additive manufacturing (AM) has drawn tremendous attention as a versatile platform for the on-demand fabrication of objects with excellent spatial control of chemical compositions and complex architectures. The development of materials that are specifically designed for AM is highly desirable for a variety of applications ranging from personal healthcare, tissue engineering, biomedical devices, self-folding origami structures, and soft robotics. Polymeric macromolecules have received increasing attention due to a wide variety of materials, the versatility for novel chemistries, and the ability to tune chemical composition and architecture. This Viewpoint highlights the development of polymeric materials for direct-ink writing and vat photopolymerization for 3D printing applications. Recent chemical innovations and polymer architectures are overviewed, which also includes recent developments in responsive and adaptive objects from AM. Polymers for biological interface and sustainability in AM are also discussed.

Synthesis and characterization of imidazolium-mediated Tröger's base containing poly(amide)-ionenes and composites with ionic liquids for CO2 separation membranes

Considerable attention has been given to polymeric membranes either containing, or built from, ionic liquids (ILs) in gas separation processes due to their selective separation of CO₂ molecules.

Sensing and Self-Sensing Actuation Methods for Ionic Polymer-Metal Composite (IPMC): A Review

Ionic polymer-metal composites (IPMC) are smart material transducers that bend in response to low-voltage stimuli and generate voltage in response to bending. IPMCs are mechanically compliant, simple in construction, and easy to cut into desired shape. This allows the designing of novel sensing and actuation systems, e.g., for soft and bio-inspired robotics. IPMC sensing can be implemented in multiple ways, resulting in significantly different sensing characteristics. This paper will review the methods and research efforts to use IPMCs as deformation sensors. We will address efforts to model the IPMC sensing phenomenon, and implementation and characteristics of different IPMC sensing methods. Proposed sensing methods are divided into active sensing, passive sensing, and self-sensing actuation (SSA), whereas the active sensing methods measure one of IPMC-generated voltage, charge, or current; passive methods measure variations in IPMC impedances, or use it in capacitive sensor element circuit, and SSA methods implement simultaneous sensing and actuation on the same IPMC sample. Frequency ranges for reliable sensing vary among the methods, and no single method has been demonstrated to be effective for sensing in the full spectrum of IPMC actuation capabilities, i.e., from DC to ∼100 Hz. However, this limitation can be overcome by combining several sensing methods.