Fused deposition modelling (FDM) is one of the mostly used additive technologies, due to its ability to produce complex parts with good mechanical properties. The selection of FDM process parameters is crucial to achieve good mechanical properties of the manufactured parts. Therefore, in this paper, a hybrid multi-criteria decision-making (MCDM) approach based on Preference Selection Index (PSI) and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) is proposed for the selection of optimal process parameters in FDM printing of polylactic acid (PLA) parts. Printing temperature, layer thickness and raster angle were considered as input process parameters. In order to prove the effectiveness of the proposed hybrid PSI – TOPSIS method, the obtained results were compared with the results obtained with different MCDM methods. The obtained best option of process parameters was confirmed by other MCDM methods. The optimal combination of process parameters to achieve the maximal flexural strength, maximal flexural modulus and maximal compressive strength is selected using the hybrid PSI-TOPSIS method. The results show that the hybrid PSI-TOPSIS approach could be used for optimisation process parameters for any machining process.

Reinforcing the polymer with nanoparticles and fibers improves the mechanical, thermal and electrical properties. Owing to this, the functional parts produced by the FDM process of such materials can be used in industrial applications. However, optimal parameters’ selection is crucial to produce parts with optimal properties, such as mechanical strength. This paper focuses on the analysis of influential process parameters on the tensile strength of FDM printed parts. Two statistical methods, RSM and ANN, were applied to investigate the effect the layer thickness, printing speed, raster angle and wall thickness on the tensile strength of test specimens printed with a short carbon fiber reinforced polyamide composite. The reduced cubic model was developed by the RSM method, and the correlation between the input parameters and the output response was analyzed by ANOVA. The results show that the layer thickness and raster angle have the most significant influence on tensile strength. As for machine learning, among the nine different tested ANN topologies, the best configuration was found based on the lowest MAE and MSE test sample result. The results show that the proposed model could be a useful tool for predicting tensile strength. Its main advantage is the reduction in time needed for experiments with the LOSO (leave one subject out) k-fold cross validation scheme, offering better generalization ability, given the small set of learning examples.

Microneedles (MNs) represent the concept of attractive, minimally invasive puncture devices of micron-sized dimensions that penetrate the skin painlessly and thus facilitate the transdermal administration of a wide range of active substances. MNs have been manufactured by a variety of production technologies, from a range of materials, but most of these manufacturing methods are time-consuming and expensive for screening new designs and making any modifications. Additive manufacturing (AM) has become one of the most revolutionary tools in the pharmaceutical field, with its unique ability to manufacture personalized dosage forms and patient-specific medical devices such as MNs. This review aims to summarize various 3D printing technologies that can produce MNs from digital models in a single step, including a survey on their benefits and drawbacks. In addition, this paper highlights current research in the field of 3D printed MN-assisted transdermal drug delivery systems and analyzes parameters affecting the mechanical properties of 3D printed MNs. The current regulatory framework associated with 3D printed MNs as well as different methods for the analysis and evaluation of 3D printed MN properties are outlined.

Microneedles (MNs) have been manufactured using a variety of methods from a range of materials, but most of them are expensive and time-consuming for screening new designs and making any modifications. Therefore, stereolithography (SLA) has emerged as a promising approach for MN fabrication due to its numerous advantages, including simplicity, low cost, and the ability to manufacture complex geometrical products at any time, including modifications to the original designs. This work aimed to print MNs using SLA technology and investigate the effects of post-printing curing conditions on the mechanical properties of 3D-printed MNs. Solid MNs were designed using CAD software and printed with grey resin (Formlabs, UK) using Form 3 printer (Formlabs, UK). MNs dimensions were 1.2 × 0.4 × 0.05 mm, arranged in 6 rows and 6 columns on a 10 × 10 mm baseplate. MNs were then immersed in an isopropyl alcohol bath to remove unpolymerized resin residues and cured in a UV-A heated chamber (Formlabs, UK). In total, nine samples were taken for each combination of curing temperature (35°C, 50°C, and 70°C) and curing time (5 min, 20 min, and 60 min). Fracture tests were conducted using a hardness apparatus TB24 (Erweka, Germany). MNs were placed on the moving probe of the machine and compressed until fracture. The optimization of the SLA process parameters for improving the strength of MNs was performed using the Taguchi method. The design of experiments was carried out based on the Taguchi L9 orthogonal array. Experimental results showed that the curing temperature has a significant influence on MN strength improvements. Improvement of the MN strength can be achieved by increasing the curing temperature and curing time.

Many different and innovative approaches have been investigated to reduce the barrier effects of the stratum corneum (SC) and one of those are microneedles. Microneedles (MNs) are micron-sized needles which assist drug delivery through skin by creating microchannels (micron-scale pores) in SC that are large enough to enable drugs, including macromolecules, to enter the skin while being small enough to avoid pain, irritation and needle phobia. They have the capacity to play a role in modern healthcare as they reduce pain, tissue damage and transmission of infection and have potential for selfadministration in comparison to traditional needles. MNs have been fabricated by a variety of methods, from a range of materials (including silicon, glass, metal, carbohydrates and polymers) and in varying geometries (Quinn et al., 2014). Additive manufacturing (AM), more commonly known as three-dimensional (3D) printing represents a new, cutting-edge technology of 3D objects fabricated from a digital model generated using computer-aided design (CAD) software by fusing or depositing proper material (e.g., ceramics, liquids, metal, plastic, powders or even living cells) in layers. Suitable thermoplastic material in the form of a filament is fed into the printer by rollers, where it is heated to just above its softening point (glass transition temperature, Tg) by heating elements into a molten state. The melted or softened material guided by gears is moved towards heat end where it is extruded from the printer’s head, through a nozzle and subsequently deposited layer-by-layer on a build plate, cooling and solidifying in under a second. The printer’s head moves within the xand y-axes, whereas the platform can move within the z-axis, thus creating 3D structures (Alhnan et al., 2016; Goole and Amighi, 2016; Jamróz, 2018; Prased and Smyth, 2016). The aim of this work was to fabricate biodegradable PLA microneedles using innovative FDM 3D-printing technology on two different 3D printers and then chemically etch their arrays to obtain ideally sized and shaped needles.

Although transdermal drug delivery systems (DDS) offer numerous benefits for patients, including the avoidance of both gastric irritation and first-pass metabolism effect, as well as improved patient compliance, only a limited number of active pharmaceutical ingredients (APIs) can be delivered accordingly. Microneedles (MNs) represent one of the most promising concepts for effective transdermal drug delivery that penetrate the protective skin barrier in a minimally invasive and painless manner. The first MNs were produced in the 90s, and since then, this field has been continually evolving. Therefore, different manufacturing methods, not only for MNs but also MN molds, are introduced, which allows for the cost-effective production of MNs for drug and vaccine delivery and even diagnostic/monitoring purposes. The focus of this review is to give a brief overview of MN characteristics, material composition, as well as the production and commercial development of MN-based systems.

Experimental Investigation and Modelling of FDM Process Parameters for Tensile Strength Improvement Using RSM Abstract Fused Deposition Modeling (FDM) is one of the most popular additive manufacturing technologies for various engineering applications. The FDM built part is especially anisotropic in nature due to layer-by-layer building mechanism. Therefore, the mechanical properties, especially the tensile strength severaly depend on the process parameters. Hence, the present work focuses on extensive study to understand the effect of four important parameters such as layer thickness, infill density, printing temperature and wall thickness on the tensile strength of test specimens. A total of 30 test specimens were printed using varying processing parameters according Central Composite Design of experiments (CCD) in order to reduce the experimental runs. The RSM method was used to generate a mathematical model, ie an equation (second order polynomial) which describes the process. Experimental results indicate that the wall thickness and infill density have the significant influence on tensile strength, and tensile strength increases with increasing wall thickeness and infill density. Printing temperature and layer thickness have less of an effect on tensile strength. Tensile strength increases with increasing printing temperature and decreases with increasing in layer thickness, especially at lower printing temperature. This paper examines the influence of selected FDM process parameters (layer thickness, infill density, printing temperature and wall thickness) on the tensile strength of the built parts. Design of experiment for doing the experiments makes use of Circumscribed Central Composite Design (CCCD). Empirical relationship between response and different process parameters is established using RSM, and its validity is checked using ANOVA. The developed relationship between tensile strength (output) and process parameters (input) is able to explain the 91.84% of variability in the response. Effect of various factors and their interactions are explained using response surface plots. It shown that the tensile strength is influenced significantly infill density and wall thickness; and less significantly printing temperature and layer thickness. In order to improve the tensile strength of FDM parts made of PLA materials, it is necessary to increase the infill density and wall thickness, decrease the layer thickness, and set the printing temperature in range 200 – 230 °C. The future research is to investigate the effect of all analyzed parameters on tensile strength for different building directions.

Fused Deposition Modeling (FDM) is one of the most popular additive manufacturing technologies for various engineering applications. Due to the mechanism of building of products on the principle of adding layer by layer, the mechanical characteristics and quality of the product directly depend on the values of process parameters. Therefore, in this paper, test tubes for mechanical properties testing and model samples for dimensional testing were made using FDM technology. Two different polymeric materials, PLA and PC, were used to make the tubes and models. During the production of test tubes and models, three more influential process parameters varied on three levels: printing temperature, infill density and layer height. The test tubes were printed and tensile tested according to the ISO 527-2 standard. Dimensional measurements were performed on the made samples of models for dimensional tests, and dimensional deviations of the finished product in relation to the designed dimensions of the 3D model were analyzed, deviations from the shape, as well as the presence of surface defects and irregularities. At the end of the paper, recommendations are given which combination of process parameters gives for both analyzed materials better mechanical characteristics and smaller dimensional deviations of the product in the manufacture of FDM technology. PLA material, where it is concluded that the model has the smallest deviation in the direction of dimensions a1 a2 and a3 if printed at a temperature of 200-230 °C, which also belongs to the recommended printing temperature by the material manufacturer. Figure 2b. shows the influence of the printing temperature on the average value of the deviation of external dimensions for PC material, where it is concluded that the model has the smallest deviation in the direction of dimensions a1 , a2 and a3 if printed at a temperature from 255-280 °C, which also belongs to the recommended printing temperature by the material manufacturer, except for the largest dimension a3 where the smallest dimensional deviations in the temperature range from 230 to 255 °C.