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•Discussion of 3D to 4D transition and its associated processes for printing.•Decoded the world of shape memory effect in materials for 4D Printing.•Potential of stimuli in 4D ...printing have been reviewed.•Parametric evaluation of materials for 4D Printing and its influences on final properties.
The idea of 3D printing ever since 1980’s has agitated the research domains challenging the conventional techniques with its inordinate efficiency in the utility of material, superior surface resolution and single step production which are applied in biomedical, electronics, self-healing and most prominently in biomimetic applications. However, this additive technique could not be controlled to produce intricate structure, to suppress strain controlled dimensional change, and anisotropic behavior. This complexity and inflexible design that had barricaded their dimension were vanquished by 4D printing with its dynamic structures. The fourth dimension conferred vitality to the design using stimulus to drive the transformation in smart materials (Shape Memory Effect or SME). Smart materials are environmentally sensitive materials comprising of polymers, alloys, hydrogels, ceramics and composites, activated by heat (pre-strain), water (absorption), electromagnetic radiations (Infrared, IR), magnetic field, ohmic parameters (current and voltage), solvent and pH. 4D printing attempts to counterfeit natural processes (flower blooming, leaf cirrus (tendrils), and sunflower movement) in drug delivery, wearable electronics, fashion wares, self-transmuting origami structures, sensors and other engineering applications. This review engulfs the evolution, burgeoning advancements and life cycle prediction of 4D printing with focusing on the smart materials and associated features like stimuli response along with future scope and challenges.
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Three-dimensional printing (3DP) is gaining momentum in the field of pharmaceuticals, offering innovative opportunities for medicine manufacture. Selective laser sintering (SLS) is a ...novel, high resolution and single-step printing technology that we have recently introduced to the pharmaceutical sciences. The aim of this work was to use SLS 3DP to fabricate printlets (3D printed tablets) with cylindrical, gyroid lattice and bi-layer structures having customisable release characteristics. Paracetamol-loaded constructs from four different pharmaceutical grade polymers including polyethylene oxide, Eudragit (L100-55 and RL) and ethyl cellulose, were created using SLS 3DP. The novel gyroid lattice structure was able to modulate the drug release from all four polymers. This work is the first to demonstrate the feasibility of using SLS to achieve customised drug release properties of several polymers, in a swift, cost-effective manner, avoiding the need to alter the formulation composition. By creating these constructs, it is therefore possible to modify drug release, which in practice, could enable the tailoring of drug performance to the patient simply by changing the 3D design.
This paper reports the thermal and mechanical properties of carbon fiber (CF) reinforced polyamide 12 (PA12) composites for fused deposition modeling (FDM) process. The printable filaments of carbon ...fiber/PA12 composites with different mass fraction were fabricated and applied in FDM. The results indicate that the tensile strength and flexural strength of 10 wt% CF/PA12 composites are enhanced by 102.2% and 251.1% respectively. The laser-flash diffusivity analysis measurements exhibit remarkable improvements on thermal conductivity (λ) of carbon fiber/PA12 composites. Moreover, the carbon fiber/PA12 composites mechanical properties are greatly improved. Our work presents a kind of anisotropic high performance composite for FDM.
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•Filament which can be smoothly printed via a FDM printer was prepared by melt compounding.•Carbon fibers are dispersed uniformly and preferentially aligned along the printing direction.•Tensile and flexure properties were improved significantly without sacrificing the impact properties.•The thermal conductivity was improved significantly.
In this study, the tensile, flexural and fracture behavior of PEEK processed by fused filament fabrication (FFF) is reported. Three different configurations, viz., specimens built horizontally with a ...raster angle of 0° (H-0°) and 90° (H-90°), and vertically with a raster angle of 90° (V-90°) are examined. The best performing specimen in terms of its tensile, flexural and fracture toughness properties is H-0°, followed by H-90° and V-90°. The H-0° and H-90° specimens exhibit 85% and 75% of tensile and flexural strengths of molded bulk PEEK, respectively. The fracture toughnesses of the H-0° and H-90° specimens are 78% and 70% of molded bulk PEEK, respectively. However, V-90° specimens show lower tensile, flexural and fracture toughness properties compared to those of H-0°, H-90° and molded PEEK. The fracture surface and microtomography analyses indicate that the degree of interfacial bonding between beads during layer-by-layer buildup, is affected by the thermal gradient across the beads. The PEEK specimen configurations examined here have different thermal gradient in the build directions and such variations manifest themselves in their macroscopic mechanical behavior. The findings of this study provide guidelines for FFF of PEEK to enable its realization in applications such as orthopedic implants.
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•Horizontally 3D printed PEEK with raster angles of 0o and 90o exhibits tensile flexural and fracture properties comparable to those of molded PEEK•Specimens built vertically are prone to delamination, exhibiting poorer mechanical performance due to high thermal gradient in the build-direction•Stick-slip fracture and lower Poisson’s ratio are observed for specimens built vertically, due to the presence of interfacial voids.•Minimizing thermal gradients across beads is the key to producing parts with excellent macroscopic properties
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•Extrusion optimization of PP and GRPP filaments for 3D printing.•3D printing vs. compression molding benchmark with the same raw material.•Optimal 3D printing conditions for PP and ...GRPP.•3D printing deposition orientation with minimum mechanical performance impact.•Reinforcing role of glass fibers is maintained with 3D printing.
This paper addresses the potential of polypropylene (PP) as a candidate for fused deposition modeling (FDM)-based 3D printing technique. The entire filament production chain is evaluated, starting with the PP pellets, filament production by extrusion and test samples printing. This strategy enables a true comparison between parts printed with parts manufactured by compression molding, using the same grade of raw material. Printed samples were mechanically characterized and the influence of filament orientation, layer thickness, infill degree and material was assessed. Regarding the latter, two grades of PP were evaluated: a glass-fiber reinforced and a neat, non-reinforced, one. The results showed the potential of the FDM to compete with conventional techniques, especially for the production of small series of parts/components; also, it was showed that this technique allows the production of parts with adequate mechanical performance and, therefore, does not need to be restricted to the production of mockups and prototypes.
Here, we present the in-plane energy absorption characteristics of modified re-entrant auxetic honeycombs realized via fused filament fabrication in conjunction with parametric analysis and geometry ...optimization. The influence and interaction effects of the geometrical parameters such as strut-length ratio and joint-angles on the stiffness, strength and energy absorption characteristics of modified re-entrant auxetic honeycombs were evaluated. Subsequently, Finite Element results obtained using ABAQUS/Explicit were corroborated with measured data. Deformation mode, stress-strain response and energy absorption behavior of an optimal re-entrant auxetic honeycomb were studied and compared with conventional re-entrant auxetic structure. Modified auxetic structure reveals an 36% improvement in the specific energy absorption capacity. Our analysis further indicates that due to the introduction of more nodes with low rotational stiffness, the failure strain of the modified re-entrant structure has increased resulting in improved energy absorption capacity.
Additive manufacturing of fiber reinforced composites is of great interest in various industrial applications. In this study, an innovative extruder is designed and manufactured for fused deposition ...modeling (FDM) 3D printers in order to produce continuous fiber reinforced thermoplastic (CFRT) composites. There are some challenges along this way such as making tension in fiber, fiber surface preparation, printing temperature and feed rate to produce a composite part with good quality. These challenges are discussed in detail. The main advantage of this extruder is that it can be mounted on the available FDM 3D printers and consequently there is no need to design a new chassis. In order to assess the quality of products, standard tensile and three-point bending specimens made of pure poly lactic acid (PLA) and carbon fiber reinforced PLA are printed and tested under quasi-static loading. Experimental results show significant improvements of tensile and bending properties of PLA. Morphological analysis is also conducted to study the bonding between the carbon fiber and PLA.
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Here, the internal structure and mechanical properties of the hydroxyapatite/polycaprolactone scaffolds, prepared by fused deposition modeling (FDM) technique, were explored. Using hydroxyapatite ...(HA) and polycaprolactone (PCL) as raw materials, nano-HA/PCL and micro-HA/PCL that composite with 20 wt% HA were prepared by melt blending technology, and HA/PCL composite tissue engineering scaffolds were prepared by self-developed melt differential FDM 3D printer. From the observation under microscope, it was found that the prepared nano-HA/PCL and micro-HA/PCL tissue engineering scaffolds have uniformly distributed and interconnected nearly rectangular pores. By observing the cross-sectional view of the nano-HA/PCL scaffold and the micro-HA/PCL scaffold, it is known that the HA particles in the nano-HA/PCL scaffold are evenly distributed and the HA particles in the micro-HA/PCL scaffold are agglomerated, which attribute nano-HA/PCL scaffolds with higher tensile strength and flexural strength than the micro-HA/PCL scaffolds. The tensile strength and flexural strength of the nano-HA/PCL specimens were 23.29 MPa and 21.39 MPa, respectively, which were 26.0% and 33.1% higher than those of the pure PCL specimens. Therefore, the bioactive nano-HA/PCL composite scaffolds prepared by melt differential FDM 3D printers should have broader application prospects in bone tissue engineering. Keywords: Fused deposition modeling FDM, Hydroxyapatite, Polycaprolactone, Porosity, Composites, Tissue engineering scaffolds, Mechanical properties
This paper provides an overview on the main additive manufacturing/3D printing technologies suitable for many satellite applications and, in particular, radio-frequency components. In fact, nowadays ...they have become capable of producing complex net-shaped or nearly net-shaped parts in materials that can be directly used as functional parts, including polymers, metals, ceramics, and composites. These technologies represent the solution for low-volume, high-value, and highly complex parts and products.
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Rheology is an indispensable tool for formulation development, which when harnessed, can both predict a material’s performance and provide valuable insight regarding the material’s ...macrostructure. However, rheological characterizations are under-utilized in 3D printing of drug formulations. In this study, viscosity measurements were used to establish a mathematical model for predicting the printability of fused deposition modelling 3D printed tablets (Printlets). The formulations were composed of polycaprolactone (PCL) with different amounts of ciprofloxacin and polyethylene glycol (PEG), and different molecular weights of PEG. With all printing parameters kept constant, both binary and ternary blends were found to extrude at nozzle temperatures of 130, 150 and 170 °C. In contrast PCL was unextrudable at 130 and 150 °C. Three standard rheological models were applied to the experimental viscosity measurements, which revealed an operating viscosity window of between 100 and 1000 Pa·s at the apparent shear rate of the nozzle. The drug release profiles of the printlets were experimentally measured over seven days. As a proof-of-concept, machine learning models were developed to predict the dissolution behaviour from the viscosity measurements. The machine learning models were discovered to accurately predict the dissolution profile, with the highest f2 similarity score value of 90.9 recorded. Therefore, the study demonstrated that using only the viscosity measurements can be employed for the simultaneous high-throughput screening of formulations that are printable and with the desired release profile.
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