Extrusion System Research Articles

Double diffusion thermal exploration of Cross nanomaterial due to moving surface with sinusoidal waves: Cattaneo–Christov model

The nanoparticles convey noteworthy applications in many engineering and industrial systems like cooling and heat processes, thermal extrusion systems, heat exchangers, as an energy source, treatment of various diseases and chemotherapy. Owing to such importance of nanomaterials, various studies are presented for nanofluids with diverse flow features. This investigation discloses an unsteady flow of Cross nanofluid over periodically accelerated imbedded in porous space. The combined heat and mass transportation aspects of nanomaterials are entertained with applications of Buongiorno’s model. Further, Cattaneo–Christov fluxes are mathematically implemented for investigating the diffusion aspect of heating and mass pattern. Additionally, the nonlinear on set of radiative distribution is followed. Referred to the suitable transformations, the independent variable in the governing system is reduced. The homotopy-based analytical expressions are obtained for set of flow parameters. The complete graphical exploration is visualized, for governing parameters, and scrutinized. The mass and heat transfer pattern has been inspected in the form of numerical data. It is perceived that velocity profile has decreasing tendency for enhancement in Weissenberg number and magneto-porous constant. The temperature and concentration profiles diminish with increase of thermal and solutal relaxation constants, respectively.

Dynamics of heat and mass transfer: Ree-Eyring nanofluid flow over a Riga plate with bioconvention and thermal radiation

Following improvements in devices used in biomedical engineering, cancer treatments, and thermal extrusion systems, this report explores the dynamics of Ree-Eyring nanofluid when subject to free convection, bioconvection, heat source, and thermal radiation over a convection-heated Riga plate. Bioconvection is assessed in light of the movement of the motile microorganisms that stabilize the dispersion of nanoparticles in the fluid. The impact of thermophoresis and Brownian motion, critical in the flow of heat and mass is also considered, together with the convective boundary condition. In many manufacturing sectors, non-Newtonian nanofluid flow is a crucial cooling component. Based on these factors, partial differential equations—the governing equations that model the transportation phenomena—are converted into nonlinear ordinary differential equations using the relevant relations. Finally, the nonlinear differential equations are solved using the homotopy analysis method (HAM), and the solutions are displayed in graphs representing distinct fluid flow parameters. It is conclusively found that the skin friction coefficient increases as the mixed convection parameter value rises, while the opposite effect is seen as the bioconvection Rayleigh number grows.

Role of the multi-drug efflux systems on the baseline susceptibility to ceftazidime/avibactam and ceftolozane/tazobactam in clinical isolates of non-carbapenemase-producing carbapenem-resistant Pseudomonas aeruginosa.

Carbapenem-resistant Pseudomonas aeruginosa (CRPA) is one of the pathogens that urgently needs new drugs and new alternatives for its control. The primary strategy to combat this bacterium is combining treatments of beta-lactam with a beta-lactamase inhibitor. The most used combinations against P. aeruginosa are ceftazidime/avibactam (CZA) and ceftolozane/tazobactam (C/T). Although mechanisms leading to CZA and C/T resistance have already been described, among which are the resistance-nodulation-division (RND) efflux pumps, the role that these extrusion systems may play in CZA, and C/T baseline susceptibility of clinical isolates remains unknown. For this purpose, 161 isolates of non-carbapenemase-producing (Non-CP) CRPA were selected, and susceptibility tests to CZA and C/T were performed in the presence and absence of the RND efflux pumps inhibitor, Phenylalanine-arginine β-naphthylamide (PAβN). In the absence of PAβN, C/T showed markedly higher activity against Non-CP-CRPA isolates than observed for CZA. These results were even more evident in isolates classified as extremely-drug resistant (XDR) or with difficult-to-treat resistance (DTR), where CZA decreased its activity up to 55.2% and 20.0%, respectively, whereas C/T did it up to 82.8% (XDR), and 73.3% (DTR). The presence of PAβN showed an increase in both CZA (37.6%) and C/T (44.6%) activity, and 25.5% of Non-CP-CRPA isolates increased their susceptibility to these two combined antibiotics. However, statistical analysis showed that only the C/T susceptibility of Non-CP-CRPA isolates was significantly increased. Although the contribution of RND activity to CZA and C/T baseline susceptibility was generally low (two-fold decrease of minimal inhibitory concentrations [MIC]), a more evident contribution was observed in a non-minor proportion of the Non-CP-CRPA isolates affected by PAβN [CZA: 25.4% (15/59); C/T: 30% (21/70)]. These isolates presented significantly higher MIC values for C/T. Therefore, we conclude that RND efflux pumps are participating in the phenomenon of baseline susceptibility to CZA and, even more, to C/T. However, the genomic diversity of clinical isolates is so great that deeper analyzes are necessary to determine which elements are directly involved in this phenomenon.

How to design, develop and build a fully-integrated melt electrowriting 3D printer

Melt electrowriting (MEW) is a high resolution material extrusion based additive manufacturing process with the unique capability to produce micron to sub-micron diameter fibres and control their deposition in three dimensions. Here, we detail the design, development and build of a custom MEW printer which has full integration between all core components. We detail the design and build of the motion system, print head (including heaters, extrusion system and high voltage power supply) and safety systems, and explain how these are integrated via a central control unit to provide pre-programmed dynamic control over printing variables allowing the fabrication of a range of advanced material designs with applications in the fields of tissue engineering, regenerative medicine and beyond. We discuss the various approaches which may be used for each system within a custom MEW printer, providing an insight into how it may be designed depending on the specific requirements of the end user. Finally, we demonstrate the capabilities of this printer by producing tissue engineering scaffolds with various architectures. This work aims to make MEW technology more accessible by both informing others interested in developing similar custom devices, and additionally, by providing an insight into the inner workings of MEW technology for practitioners in the field.

Thermal stable properties of solid hybrid nanoparticles for mixed convection flow with slip features

Following to improved thermal impact of hybrid nanomaterials, wide range applications of such materials is observed in the thermal engineering, extrusion systems, solar energy, power generation, heat transfer devices etc. The hybrid nanofluid is a modified form of nanofluid which is beneficial for improving energy transfer efficiency. In current analysis, the solid nanoparticles aluminium (phi_{{{text{Al}}_{2} {text{O}}_{3} }}) and copper (phi_{{{text{Cu}}}}) have been mixed with water to produce a new hybrid nanofluid. The investigation of a steady two-dimensional mixed convection boundary layer flow of the resultant hybrid nanofluid on a vertical exponential shrunk surface in the existence of porous, magnetic, thermal radiation, velocity, and thermal slip conditions is carried out. Exponential similarity variables are adopted to transform the nonlinear partial differential equation into a system of ordinary differential equations which has been then solved by employing the shooting method in Maple software. The obtained numerical results such as coefficient of skin friction f^{prime prime } left( 0 right), heat transfer rate - theta^{prime } left( 0 right), velocity f^{prime } left( eta right) and temperature left( {theta left( eta right)} right) distributions are presented in the form of different graphs. The results revealed that duality exists in solution when the suction parameter S ge S_{ci} in assisting flow case. Due to non-uniqueness of solutions, a temporal stability analysis needs to be performed and the result indicates that the upper branch is stable and realizable compared to the lower branch.

Effects of Part Orientation, Printer Selection, and Infill Density on Mechanical Properties and Production Cost of 3D Printed Flexural Specimens

This work investigates the influence of infill density, printer selection, and part orientation on the mechanical properties and production cost of flexural specimens fabricated using material extrusion additive manufacturing systems. Flexural test specimens are fabricated in both production-grade (Fortus 250mc) and entry-level (MakerBot Replicator 2X) material extrusion systems with varying infill densities (1 mm to 10 mm spacing between rasters). In addition, solid infill specimens are printed in three orientations to establish baseline mechanical stiffness and strength. Finite element simulations and a simplified analytical model based on Euler-Bernoulli beam theory are developed. Results show reasonable agreement between analytical, simulation, and experimental results; 10-20% and 10-40% deviation for production-grade and entry-level specimens, respectively. There is a 40% reduction in stiffness and strength between the solid XY specimen and 1 mm infill specimen. As infill density is further decreased, stiffness and strength asymptotically reduce by 60-70% when compared to solid specimens. This effect is more pronounced in specimens fabricated using entry-level printers, which indicates that printer selection plays a role in printing highly sparse parts. Cost analysis suggests that up to 40% savings can be achieved with highly sparse structures. However, for structural parts, it is recommended that parts be printed with solid infill and with the loading direction aligned in the XY plane to achieve high stiffness, high strength, and reasonable cost. Findings from this study show that there is minimal cost savings but high reduction in mechanical stiffness and strength when sparse infills are used in both production-grade and entry-level printers. Hence, it is recommended that solid infill should be used in all regions of parts that carry significant mechanical stress and sparse infill be used solely to support internal geometries and overhangs.

Couple stress Darcy–Forchheimer nanofluid flow by a stretchable surface with nonuniform heat source and suction/injection effects

The thermal enhancement of industrial and engineering processes with interaction of nanofluids is exclusively important and presents applications in extrusion systems, heat transfer devices, electronic chips, chemical reactions, nuclear processes, etc. Owing to such motivated significance of nanofluids, the aim of this investigation is to present the heat and mass transfer phenomenon in the Couple stress nanofluid flow containing the microorganism due to oscillatory stretched surface. Additionally, the Darcy–Forchheimer applications, nonuniform heat source and nonlinear thermal radiation effects are considered. The modification in the concentration equation is done by activation energy. The independent variables in the defined flow system are decreased via suitable variables. The computation is simulated using the homotopy analysis method. It is noticed that the magnitude of velocity periodically decreases for larger values of suction parameter and inertia coefficient. The presence of an external heat source parameter enhanced the temperature profile. Moreover, the increment in the suction parameter improves the heat and mass transfer rate.

Experimental and Numerical Analysis of Single Screw Extrusion Process for Thermoplastic PBX Based on PVT Properties

Much of surplus ammunition stockpile inevitably requires demilitarized processing technology in the explosives industry. For the safe waste treatment and recycle, the thermoplastic polymer bonded explosive (PBX) can effectively reduce the military cost and non-conforming products. In addition, the thermoplastic PBX has excellent application prospect as the future explosive due to the good mechanical properties and insensitivity. However, for high solid content, most of thermoplastic PBXs still maintain a considerable viscosity even in high-temperature melting state, rendering traditional casting process unsuitable. In this study, a measuring method was adopted to accurately obtain the correlation of Pressure-Volume-Temperature (PVT) for the simulative materials of thermoplastic PBX at first. The equations of state for PVT and viscosity model were then created, which are of great significance in single screw extrusion. An experiment system of single screw extrusion was designed to implement the molding process considering the poor liquidity problem of the thermoplastic materials. Excellent molding stability (ρ<0.5 % variation) was achieved for the extrusion system. Moreover, a numerical investigation was also performed. Good agreements were yielded by comparing the simulation data and experimental results. The effects of operational parameters, i. e., the entrance pressure, barrel temperature and rotation speed on molding process of the thermoplastic materials were investigated in detail. The wall shear stress decreases with the feed inlet well sealed whereas the maximum temperature rise increases a little due to limited thermal diffusion. Either increasing temperature or decreasing rotation speed is beneficial to overall process safety. However, production cycle and attainable molding density also need to be considered at the same time. Furthermore, the process parameters should be optimized on the basis of the PVT and viscosity properties of material in practice. The investigations above can be a better guidance for the development and implementation of thermoplastic PBXs molding process.

Strength of Contact Geometry for Multi‐material 3D‐Printed Samples

AbstractFused filament fabrication is an extrusion‐based additive manufacturing technology with relatively low‐cost equipment and a great variety of materials from standard to engineering grade. Multiple extrusion systems allow for new opportunities regarding the manufacturing of multi‐color and multi‐material parts. However, regular bond formation of part's bodies provided by the slicing tool offers good results regarding the resulting product's dimensional stability but poor mechanical properties. For this reason, this paper aims to investigate if the mechanical properties of compatible polymers can be enhanced by modifying the regular flat to a flat surface with different shape interfaces and an overlap degree between them. Furthermore, for a broader understanding of the bond formation, the design of the experiment comprises two groups referring to the material blend along with their melting ranges and join geometry, which is constrained with regard to nozzle output size. The results show that the mechanical properties of multi‐material bonds can be enhanced conveniently by adding an overlap degree between mating bodies.

Analysing the Exponentially Varying Viscosity of Micropolar Carreau Nanofluid Flow with Variable Fluid Properties in Stretching Porous Sheet

In this study, the researchers assumed a thermal energy system with variable controlling properties, mainly like varying viscosity parameters, and power-law index, which has an impact on the overall procedure. Variable thermo-physical features of induced magnetic field on Carreau flow settled with micropolar nanofluid are explored on account of wide range of applications. The micropolar fluids theory focuses on a type of fluids that have tiny effects resulting from the fluid’s micro-motions. Evaluating an micropolar nanofluid’s electrically conducting flows in magnetohydrodynamic (MHD) by virtue of the thermal device is crucial in present metalworking and metallurgy processes. Therefore, the proposed research came with a novel method of neural network with optimization technique also to calculate the accurate result of varying parameters. The obtained differential equation with partial derivatives is transformed into differential equations with ordinary coefficients using the transformation functions. Consecutively, the differential equations with ordinary coefficients are solved using the solution methods of Adam predictor collector and Runge Kutta Fehlberg methods. The thermal extrusion system includes profiles of angular velocity, velocity, concentration, magnetic field, and temperature, in addition to the governing parameters for each. The effectiveness of values acquired by the solution approach was inadequate to continue the investigation, thus a neural network based quaternion values technique was used in solving differential equations to obtain the optimized values of the novel parameters studied in this research. The Mat Lab software is used to carry out for this research’s execution. The research focuses on the varying parameter of viscosity of the nanofluid, therefore the profiles considered was resultant as that the concentration, temperature, and angular velocity profiles decreases as the values of 0.233886, 0.220491, and 0.107346 in addition to a rise in viscosity parameter. However, the velocity rises with the value of 0.970122 as the viscosity parameter values are steadily increased. The effect of utilizing a genetic algorithm based quaternion neural network to optimise the values of the result is compared to two other optimization strategies (MLP + GA and MLP + GD), moreover to the solved numerical values. The novel optimization technique with neural networks gives a better result than the existing methods and the solved numerical values. As a result, this study examined at the MHD based micropolar Carreau nanofluid’s mass and heat transfer on a permeable stretching surface of an induced magnetic field, and it came up with accurate values optimised by a novel neural network model with a genetic algorithm, which gives less error in training and testing data.

In-situ constructing highly oriented ductile poly(3-hydroxybutyrate-co-3-hydroxyvalerate) nanoribbons: Towards strong, ductile, and good heat-resistant polylactic-based composites

It remains a great challenge to manufacture polylactic (PLA) with high strength, ductility, and heat resistance simultaneously. Herein, PLA/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanoribboned composites, the highly oriented PHBV nanoribbons decorated by the PLA lamella, are successfully achieved through the multistage stretching extrusion (MSE) system. SEM confirms that in-situ highly oriented PHBV nanoribbons are achieved by biaxial-stretching field during the MSE process. Through investigating crystalline architecture of PLA/PHBV nanoribboned composites, it is found that the stiff shish and sparse lamellae of PLA are obtained under the coupling effect of PHBV nanoribbons and biaxial-stretching field. DMA reveals partial compatibility between PLA and PHBV. Interestingly, during tensile test, PHBV nanoribbons show high flexibility and synergistically facilitate the stretch of semi-rigid chains of PLA by an effective interfacial interaction. Consequently, even they both are extremely brittle, PLA/PHBV nanoribboned composites exhibit excellent strength (82.9 MPa) and ductility (186.7 %), compared with pure PLA (71.4 MPa and 12.3 %). Additionally, due to the promotion of the crystallization of PLA, PLA/PHBV nanoribboned composites show excellent heat resistance (E′140°C > 350 MPa). The nanoribboned composites are of immense significance, which provide significant guidance for the simultaneous enhancement of ductility and strength of polymer materials.

Material Extrusion Advanced Manufacturing of Helical Artificial Muscles from Shape Memory Polymer

Rehabilitation and mobility assistance using robotic orthosis or exoskeletons have shown potential in aiding those with musculoskeletal disorders. Artificial muscles are the main component used to drive robotics and bio-assistive devices. However, current fabrication methods to produce artificial muscles are technically challenging and laborious for medical staff at clinics and hospitals. This study aims to investigate a printhead system for material extrusion of helical polymer artificial muscles. In the proposed system, an internal fluted mandrel within the printhead and a temperature control module were used simultaneously to solidify and stereotype polymer filaments prior to extrusion from the printhead with a helical shape. Numerical simulation was applied to determine the optimal printhead design, as well as analyze the coupling effects and sensitivity of the printhead geometries on artificial muscle fabrication. Based on the simulation analysis, the printhead system was designed, fabricated, and operated to extrude helical filaments using polylactic acid. The diameter, thickness, and pitch of the extruded filaments were compared to the corresponding geometries of the mandrel to validate the fabrication accuracy. Finally, a printed filament was programmed and actuated to test its functionality as a helical artificial muscle. The proposed printhead system not only allows for the stationary extrusion of helical artificial muscles but is also compatible with commercial 3D printers to freeform print helical artificial muscle groups in the future.

Development of a Hot-Melt-Extrusion-Based Spinning Process to Produce Pharmaceutical Fibers and Yarns.

Fibers and yarns are part of everyday life. So far, fibers that are also used pharmaceutically have mainly been produced by electrospinning. The common use of spinning oils and the excipients they contain, in connection with production by melt extrusion, poses a regulatory challenge for pharmaceutically usable fibers. In this publication, a newly developed small-scale direct-spinning melt extrusion system is described, and the pharmaceutically useful polyvinyl filaments produced with it are characterized. The major parts of the system were newly developed or extensively modified and manufactured cost-effectively within a short time using rapid prototyping (3D printing) from various materials. For example, a stainless-steel spinneret was developed in a splice design for a table-top melt extrusion system that can be used in the pharmaceutical industry. The direct processing of the extruded fibers was made possible by a spinning system developed called Spinning-Rosi, which operates continuously and directly in the extrusion process and eliminates the need for spinning oils. In order to prevent instabilities in the product, further modifications were also made to the process, such as a the moisture encapsulation of the melt extrusion line at certain points, which resulted in a bubble-free extrudate with high tensile strength, even in a melt extrusion line without built-in venting.

Additive manufacturing of polyaniline electrodes for electrochemical applications

Polyaniline (PANI), particularly in its emeraldine salt form (PANI-ES), possesses several desirable properties such as high tuneable conductivity, pseudocapacitance and chemical stability, which make PANI a promising material for a wide range of electrochemical applications. However, its use is severely limited by its poor processability due to its non-thermoformable nature. In this work, a novel additive manufacturing method to process PANI is introduced, which enables the fabrication of electrodes with complex geometries exhibiting conductivities of up to 20000 mS/cm. This novel additive manufacturing process is based on the thermal doping of PANI in its low-conductive emeraldine base form (PANI-EB) with dodecyl benzene sulfonic acid (DBSA). For this purpose, a commercially available 3D printer was modified with a custom-made syringe extrusion system to enable the extrusion of a viscous PANI-EB/DBSA paste. The influence of the additive manufacturing process parameters on the conductivity of printed electrodes was evaluated, and the resulting printed materials were characterised by Fourier-transform infrared spectroscopy – attenuated total reflection, X-ray powder diffraction, thermo-gravimetric analysis and scanning electron microscopy. The feasibility of the 3D printed PANI-ES/DBSA electrodes was studied by conducting a proof-of-concept electrochemical study of 3D printed interdigitated symmetric electrochemical capacitors, demonstrating how the printed structures could be easily integrated in prototypes of electrochemical devices. Although the fabricated devices did not exhibit superior capacitance, they presented a memristive behaviour with a potential for other applications such as artificial neural networks. Moreover, the results of this proof-of-concept study illustrate the significant importance of the conductivity of the printed electrodes, hence the importance of the additive manufacturing process parameters on the electrochemical performance.

Effect of fatty acid saturation degree on the rheological properties of pea protein and its high-moisture extruded product quality

To provide a deep insight into the application of lipid in plant protein-based meat substitutes through high-moisture extrusion (HME) process, the effect of fatty acid saturation degree (stearic acid, oleic acid and linoleic acid) on the rheological and structural properties of pea protein isolate (PPI), and its relationship with the extrusion system parameters and extrudate qualities were investigated. The oleic acid and linoleic acid significantly decreased the apparent viscosity of PPI dispersion and thus reduced the die pressure and torque during HME processing. Electrophoresis and Fourier transform infrared spectroscopy results revealed that fatty acids inhibited the aggregation of legumin and vicilin subunits at 50 and 20 kDa, and promoted the conversion of α-helix and β-sheet to β-turn and random coil. The macro- and micro-structure observation and texture analysis suggested that the fatty acids with higher unsaturation degree were not advantageous for the pea protein fibrous structure improvement during HME process.

Compounding a High-Permittivity Thermoplastic Material and Its Applicability in Manufacturing of Microwave Photonic Crystals.

Additive Manufacturing (AM) techniques allow the production of complex geometries unattainable through other traditional technologies. This advantage lends itself well to rapidly iterating and improving upon the design of microwave photonic crystals, which are structures with intricate, repeating features. The issue tackled by this work involves compounding a high-permittivity material that can be used to produce 3D microwave photonic structures using polymer extrusion-based AM techniques. This material was acrylonitrile butadiene styrene (ABS)-based and used barium titanate (BaTiO3) ceramic as the high-permittivity component of the composite and involved the use of a surfactant and a plasticizer to facilitate processing. Initial small amounts of the material were compounded using an internal batch mixer and studied using polymer thermal analysis techniques, such as thermogravimetric analysis, rheometry, and differential scanning calorimetry to determine the proper processing conditions. The production of the material was then scaled up using a twin-screw extruder system, producing homogeneous pellets. Finally, the thermoplastic composite was used with a screw-based, material extrusion additive manufacturing technique to produce a slab for measuring the relative permittivity of the material, as well as a preliminary 3D photonic crystal. The real part of the permittivity was measured to be 12.85 (loss tangent = 0.046) in the range of 10 to 12 GHz, representing the highest permittivity ever demonstrated for a thermoplastic AM composite at microwave frequencies.

Influence of contact geometry over the filament bond of polylactic acid blends

Fused Filament Fabrication is one of the most common Additive Manufacturing technologies among industrial and domestic users because of the satisfying quality of parts and the great variety of thermoplastic polymers available on the market. New possibilities were provided along with the equipment with multiple extrusion systems, referring to multi-colour and multi-material components. Besides part orientation during the manufacturing process, filament bond influences the mechanical properties of parts produced through Fused Filament Fabrication technology. This paper aims to investigate if the bond performance for polylactic acid-based polymers can be enhanced by designing new contact geometries, different from the current surface-to-surface approach. To comprehensively understand the influence of the designed bonding geometries over the tensile strength, all specimens were produced according to a factorial design of experiment method and contact geometries constrained with function related to the nozzle size.

Effects of extrusion parameters on properties of 3D printing concrete with coarse aggregates

Different extrusion systems have been widely used in previous studies, researches on the influence of nozzle directions and scrapers on properties of 3D printing concrete (3DPC) were however very limited. Therefore, the buildability, mechanical properties, and microstructure of concrete printed by different nozzle directions and scrapers were studied in this investigation. It has been found that the vertical extrusion force would reduce buildability, whereas increase the mechanical properties of 3DPC. Microstructure indicates that the interlayer porosity of concrete printed by vertical nozzle is 79.8% of that printed by horizontal nozzle. Besides, compared with the vertical nozzle without scraper (VN), the vertical nozzle with 40 mm-height scrapers (VN-40S) could reduce the vertical deformation of 3DPC by 20%−25% and increase the flexural strength parallel to the printing direction of 3DPC by 44%–49%. The interlayer porosity of concrete printed by VN-40S is 70.1% of that printed by VN. Longer scrapers could influence more printed layer fresh concrete, so the porosity is further reduced. Finally, a discrete element method (DEM) and automatic scraper system are discussed for the future work of 3DPC.

Development of a 3D Printer for the Manufacture of Functional Food Protein Gels.

The use of additive manufacturing is growing in multiple sectors, including food, and its scientific and technological challenges form the subject of much ongoing research. One current hurdle is the implementation of the 3D printing process for meat protein matrices. This article gives an overview of the various 3D printers used to study the printability properties of foods and presents the development of a 3D printer designed to print food protein gels. Printhead development (flow rate and temperature control) and the modifications made to the printing plate (temperature control) are described and discussed in relation to the constraints highlighted in a first prototype. A second, developed prototype was characterized and validated. This last phase showed perfect control of the prototype in the purging of the extrusion system, the flow rate, the calibration and the displacement of the printhead, along with the temperatures at both printhead and plate. A study of the printed gels also revealed good repeatability of the printed gel geometry and pointed to new ways to improve the process. In the near future, the protein gels that will be printed from this prototype will serve as a base for texturizer-free functional foods for people with chewing difficulties.

ITIL: Interlaced Topologically Interlocking Lattice for continuous dual-material extrusion

Material Extrusion (MEX) systems with dual-material capability can unlock interesting applications where flexible and rigid materials are combined. When chemically incompatible materials are concerned the adhesion between the two might be insufficient. Therefore researchers typically rely on dovetail type interlocking geometries in order to affix two bodies mechanically. However, dovetail type interlocking introduces extrusion discontinuities and relies on the material’s resistance to deformation, which is difficult to model. We propose a simple and effective 3D lattice consisting of interlaced horizontal beams in vertically alternating directions which interlock topologically: the interlaced topologically interlocking lattice (ITIL). It ensures continuous extrusion and ensures an interlock even for highly flexible materials. We develop analytical models for optimizing the ultimate tensile strength of the ITIL lattice in two different orientations relative to the interface: straight and diagonal. The analytical models are applied to polypropylene (PP) and polylactic acid (PLA) and verified by finite elements method (FEM) simulations and physical tensile experiments. In the diagonal orientation ITIL can obtain 82% of the theoretical upper bound of 8 . 6 MPa . ITIL seems to perform comparably to dovetail interlocking designs, while it lends itself to application to non-vertical interfaces. Optimizing the lattice for non-vertical interfaces, however, remains future work. • Topological interlocking does not rely on the material’s tendency to deform. • Topological interlocking can satisfy extrusion continuity constraints. • Which lattice is strongest depends on the space available for interlocking. • The tensile strength of any interlock cannot exceed a theoretical upper bound. • Tensile properties of our lattice can are well approximated by analytical models.