Multi-material Fused Deposition Modeling Research Articles

Tribological behavior of PEEK based composites with alternating layered structure fabricated via fused deposition modeling

In the present study, novel polyether ether ketone (PEEK) based composites were fabricated by multi-material fused deposition modeling (FDM), which were composed of alternating short carbon fiber reinforced PEEK and silicon dioxide filled PEEK layers. And the composites’ tribological properties were evaluated in order to guide their application in industrial parts where friction and wear are of special importance. It is revealed that the tribological properties of the composite were highly dependent on the contact pressure. The low friction and wear occurred at high contact pressure was found to be associated with the combined contribution of rolling of nanoparticles and graphitized self-lubricating transfer films. This work provides a simple strategy for manufacturing highly customized tribo-components with required functions to replace conventional hybrid materials.

Mechanical behavior of interpenetrating phase composite structures based on triply periodic minimal surface lattices

The triple periodic minimal surface (TPMS) structures have received widespread attention due to their excellent mechanical properties, such as high specific strength and energy absorption. However, these structures are prone to suffering catastrophic damage due to stress concentration and shear deformation in actual loading environments, affecting their load-bearing performance. In this work, interpenetrating phase composite (IPC) structures were fabricated by filling thermoplastic polyurethane (TPU) as a soft material into the diamond minimal surface structure using the multi-material fused deposition modeling technique, and their mechanical behavior was investigated numerically and experimentally. The effects of topological types and volume fractions on the performance of IPC structures were investigated. It is shown that the IPC structure undergoes stretching-dominated deformation, and its strength and toughness are significantly improved compared to the TPMS structure. Due to the addition of a complementary phase structure made of TPU, stress concentration and shear failure are reduced. The global deformation of the IPC structure and stress distribution of the TPMS phase are more uniform, effectively protecting the entire structure from catastrophic failure.

Multi-material additive manufacturing via fused deposition modeling 3D printing: A systematic review on the material feeding mechanism

The rapid advancements in fused deposition modeling (FDM) 3D printing methods have unlocked new opportunities in multi-material additive manufacturing (AM). This technique offers a viable solution for creating high-performance, multi-functional graded materials, parts, and tooling. Despite the extensive efforts invested in exploring the potential of the FDM-type multi-material additive approach, there is a noticeable lack of discussion specifically centered around the material feeding mechanism of this extrusion-based 3D printing method. This work provides a systematic review on the current studies related to the multi-material FDM 3D printing. It is found that the interlayer adhesion quality of different feedstock materials is a first and foremost feature in determining the strength of the entire print. To this end, we particularly focus on analyzing the feeding system of multiple materials and the strategy for material alternation. From our analytical evaluations, it is noticed that the single-nozzle/multi-feed and multi-nozzle/multi-feed FDM printers present unique pros. and cons., respectively. Inspired by multi-material applications of direct ink writing extrusion-based 3D printing, we also suggest to choose a suitable method based on the material rheology and thermal properties of the constituent materials. This can be a chance to gain further benefits from the multi-material AM.

Polycaprolactone with multiscale porosity and patterned surface topography prepared using sacrificial 3D printed moulds: Towards tailor-made scaffolds

Biocompatible three-dimensional porous scaffolds are widely used in multiple biomedical applications. However, the fabrication of tailor-made 3D structures with controlled and combined multiscale macroscopic-microscopic, surface and inner porosities in a straightforward manner is still a current challenge. Herein, we use multimaterial fused deposition modeling (FDM) to generate poly (vinyl alcohol) (PVA) sacrificial moulds filled with poly (Ɛ-caprolactone) (PCL) to generate well defined PCL 3D objects. Further on, the supercritical CO2 (SCCO2) technique, as well as the breath figures mechanism (BFs), were additionally employed to fabricate specific porous structures at the core and surfaces of the 3D PCL object, respectively. The biocompatibility of the resulting multiporous 3D structures was tested in vitro and in vivo, and the versatility of the approach was assessed by generating a vertebra model fully tunable at multiple pore size levels. In sum, the combinatorial strategy to generate porous scaffolds offers unique possibilities to fabricate intricate structures by combining the advantages of additive manufacturing (AM), which provides flexibility and versatility to generate large sized 3D structures, with advantages of the SCCO2 and BFs techniques, which allow to finely tune the macro and micro porosity at material surface and material core levels.

Analysis and Development Technique of a Fully 3-D-Printed Differential Capacitive Anemometric Sensor

Current developments in the field of 3-D printing have employed embedded electronics, in order to implement innovative devices and sensors. In this work, we present the analysis, fabrication, and experimental results of a novel, fully 3-D printable differential capacitive anemometric sensor for low-power applications. The system exploits a multimaterial fused deposition modeling (FDM) technology to print standard polylactic acid (PLA) filament as well as electrically conductive filament, employed to implement a differential capacitive air pressure sensor, embedded in a printed spherical structure, able to measure the wind speed. A theoretical analysis for the mechanical structure design, focusing on the 3-D printed bending behavior, as well as for fluid dynamics of the sensor and the electronic circuitry design has been conducted. Simulations and measurements of the fabricated prototype have demonstrated the feasibility of the proposed wind sensor. Differential capacitive variations have been observed by applying constant airflow through the sensor, showing a good agreement with the simulated behavior.

A new boundary interlock geometry design pattern to strengthen FDM part multi-material interface

Multi-material Fused Deposition Modeling (FDM) enables the realization of designs in complex geometries with multiple materials. However, achieving an adequate level of interfacial bonding strength between different materials remains a significant challenge. Other than addressing this challenge through material bonding at molecular scale or optimizing the printing parameters, new design methodologies also pose good potential. This work studied the mechanical properties of multi-material printed objects, with a particular focus on the interface zone built between the various materials at their geometrical borders. Four types of test samples were designed, printed, and tested: (A) single-material test samples uni-body (without boundary interface); (B) single-material test samples with planar boundary interface; (C) bi-material test samples with a planar boundary interface; and (D) bi-material test samples with new boundary interlock geometry design interface. The comparison of the mechanical performance between Type-A, -B, and -C test samples demonstrated the influence of the presence of a geometrical boundary interface between the same material and different materials. The comparison between Type-C and -D demonstrated the impact of introducing boundary interlock geometry. This study showed that with the new boundary interlock geometry design, the mechanical strength (tensile strength) of multi-material prints can be greatly improved. Furthermore, a Design of Experiment is conducted to identify the interlock geometry design parameters optimized for tensile strength. This work proves the significance of boundary interlock geometry design in multi-material printing and provides a methodology to explore new boundary interlock geometry design patterns to strengthen the FDM part multi-material interface.

Smart structures with embedded flexible sensors fabricated by fused deposition modeling-based multimaterial 3D printing

ABSTRACT Smart structures have the advantages of high system integrity and diverse sensing capabilities. However, the labor-intensive and time-consuming fabrication process hinders the large-scale adoption of smart structures. Despite recent attempts to develop sensor-embedded structures using 3D printing technologies, the reported smart structures generally suffer from the complex fabrication process, constrained part size, and limited sensing modality. Herein, we propose a workflow to design and fabricate novel smart structures via multimaterial fused deposition modeling (FDM)-based 3D printing. More specifically, conductive filaments with tailorable mechanical and electrical properties, e.g. piezoresistive effects, were developed. Additionally, the printing process was optimized for processing soft filaments with Young’s modulus around 2 MPa, resolving the issue of filament buckling. Furthermore, the potential applications of the proposed workflow were showcased using three design cases, i.e. biaxial strain sensor, smart tire, and cable-driven soft finger with multiple sensing capabilities. This workflow provides a cost-effective and rapid solution for developing novel smart structures with soft materials.

Multi-material topology optimization and additive manufacturing for metamaterials incorporating double negative indexes of Poisson’s ratio and thermal expansion

Advances in the multi-material additive manufacturing promote a new opportunity for developing metamaterials integrating complex functionalities, especially the metamaterial incorporating double negative indexes of Poisson’s ratio and thermal expansion. However, the systematic design and additive manufacturing of such metamaterial are stilling not developed. Here, an improved multi-material topology optimization method, Alternating Active Phase & Objective (AAPO) algorithm, was developed. A new optimization formulation, in which the core contribution was the dynamical switch of the objective functions according to the active phases, was proposed to successfully overcome the convergence oscillation. The optimization formulation and sensitivity analysis based on the numerical homogenization were established. A series of multi-material re-entrant and chiral metamaterials, which exclusively realized the double negative indexes of Poisson’s ratio and thermal expansion, were devised. Especially, the tri-material and chiral metamaterials were originally obtained through the topology optimization. More importantly, metamaterials were well additively manufactured through the multi-material fused deposition modeling. The experimentally tested Poisson’s ratio and thermal expansion suggest a good agreement between the experiments and topology-optimized results. The multi-material design and additive manufacturing developed here provide a general guidance to develop the multi-functional metamaterials.

Solution Foaming-Treated 3D-Printed monolithic packing for enhanced solid phase extraction of trace metals.

Post-printing treatment is a promising means of enhancing the performance of devices manufactured using conventional three-dimensional printing (3DP) technologies. In this study we developed a post-printing solution foaming process-involving respective treatment with formic acid (60%, v/v) and sodium bicarbonate (5%, w/v) solutions to generate CO2 as a foaming agent-to increase the surface roughness and porosity of the polyamide 6 (PA6) monolithic packing in a multimaterial fused deposition modeling 3D-printed solid phase extraction (SPE) column, thereby enhancing the extraction of Mn, Co, Ni, Cu, Zn, Cd, and Pb ions from complicated real samples prior to their determination using inductively coupled plasma mass spectrometry. After optimizing the column fabrication process, the solution foaming treatment process, the extraction conditions, and the automatic analytical system, the 3D-printed SPE column incorporating the solution foaming-treated PA6 monolithic packing extracted these metal ions with 18.9- to 42.0-fold enhancements, relative to those of the as-printed column, with absolute extraction efficiencies all greater than 94.3% and method detection limits ranging from 0.2 to 7.7ngL-1. We verified the reliability and applicability of this method through analyses of the tested metal ions in several reference materials (CASS-4, SLEW-3, 1643f, and 2670a) and spike analyses of seawater, river water, ground water, and urine samples. We conclude that post-printing treatment can dramatically improve the performance of 3D-printed analytical devices.

Using multi-material fused deposition modeling (FDM) for one-step 3D printing of microfluidic capillary electrophoresis with integrated electrodes for capacitively coupled contactless conductivity detection

For the first time, the fused deposition modeling (FDM) 3D printing method was used to fabricate a microchip capillary electrophoresis (MCE) with channel dimensions (58 × 65 µm) below 100 µm. Moreover, electrodes to conduct capacitively coupled contactless conductivity detection (C4D) were integrated into the MCE using three conductive thermoplastic filaments containing graphene, carbon black, and copper. After optimizing the parameters for multi-material printing, the MCE-C4D device was fabricated in a single (one step) 3D printing process using an FDM 3D printer equipped with two extrusion nozzles. An optimization design method allowed finding that the distance (gap) between the electrodes of around 1 mm provided the maximum response of the C4D. The optimized frequency of the excitation signal applied in the C4D electrodes depended on the composition of the conductive filament used to print the electrodes. The optimized frequencies for the electrodes printed with thermoplastic polymers containing copper and carbon black were 268 and 384 kHz, respectively. The MCE-C4D successfully separated and detected a mixture of K+, Na+, and Li+ with good resolution, efficiency, precision, linearity, and limits of detections (LOD) of 10.2, 11.6, and 14.1 µmol L-1, respectively.

4D-printed pH sensing claw

As an example of extending the functionality of analytical devices manufactured using four-dimensional printing (4DP), in this study we employed acrylonitrile butadiene styrene (ABS) thermoplastic filaments, poly(4-vinylpyridine) (P4VP)-incorporated ABS filaments, and multi-material fused deposition modeling three-dimensional printing (3DP) to fabricate a pH measurement device that underwent pH-dependent geometric changes. Upon immersion in a solution having a pH close to the value of pKa of P4VP (ca. 5.0), electrostatic repulsion among the protonated units of P4VP resulted in swelling only of the part printed using the P4VP-incorporated ABS filaments, leading to lifting of the whole device along the z-axis (ΔH) in a pH-dependent manner. After optimizing the device's design and fabrication, this 4D-printed pH sensing claw exhibited linearity between the value of ΔH and values of pH in the range from 5.0 to 8.6. We used this 4D-printed pH sensing claw to perform pH analyses of complicated real samples, verifying its analytical reliability for non-electrochemical and non-optical pH measurement and highlighting the capability of 4DP technologies in the direct fabrication of stimuli-responsive sensing devices. We envision that 4DP technologies will prompt the manufacture of smart sensing devices through the printing of stimuli-responsive materials, thereby diversifying the development of 3DP-enabling analytical chemistry.

Using Multi-Material Fused Deposition Modeling (Fdm) for One-Step 3d Printing of a Microfluidic Capillary Electrophoresis Device with Integrated Electrodes for Capacitively Coupled Contactless Conductivity Detection

Using Multi-Material Fused Deposition Modeling (Fdm) for One-Step 3d Printing of a Microfluidic Capillary Electrophoresis Device with Integrated Electrodes for Capacitively Coupled Contactless Conductivity Detection

Dimensions of Smart Additive Manufacturing

Dimensions of Smart Additive Manufacturing

Fabrication of a Soft Robotic Gripper With Integrated Strain Sensing Elements Using Multi-Material Additive Manufacturing.

With the purpose of making soft robotic structures with embedded sensors, additive manufacturing techniques like fused deposition modeling (FDM) are popular. Thermoplastic polyurethane (TPU) filaments, with and without conductive fillers, are now commercially available. However, conventional FDM still has some limitations because of the marginal compatibility with soft materials. Material selection criteria for the available material options for FDM have not been established. In this study, an open-source soft robotic gripper design has been used to evaluate the FDM printing of TPU structures with integrated strain sensing elements in order to provide some guidelines for the material selection when an elastomer and a soft piezoresistive sensor are combined. Such soft grippers, with integrated strain sensing elements, were successfully printed using a multi-material FDM 3D printer. Characterization of the integrated piezoresistive sensor function, using dynamic tensile testing, revealed that the sensors exhibited good linearity up to 30% strain, which was sufficient for the deformation range of the selected gripper structure. Grippers produced using four different TPU materials were used to investigate the effect of the Shore hardness of the TPU on the piezoresistive sensor properties. The results indicated that the in situ printed strain sensing elements on the soft gripper were able to detect the deformation of the structure when the tentacles of the gripper were open or closed. The sensor signal could differentiate between the picking of small or big objects and when an obstacle prevented the tentacles from opening. Interestingly, the sensors embedded in the tentacles exhibited good reproducibility and linearity, and the sensitivity of the sensor response changed with the Shore hardness of the gripper. Correlation between TPU Shore hardness, used for the gripper body and sensitivity of the integrated in situ strain sensing elements, showed that material selection affects the sensor signal significantly.

3D Printed Metamaterial Capacitive Sensing Array for Universal Jamming Gripper and Human Joint Wearables

Existing stretchable capacitive sensor arrays face challenges in decoupling normal forces and stretch stimuli which restrict its applications into soft robotics. Herein, a metamaterial capacitive sensor array with 6 × 6 sensors is developed for the detection of normal forces on curved deforming surfaces common to both the soft universal jamming gripper and human elbow. The fabrication process involves the 3D printing of carbon black thermoplastic polyurethane (PI–ETPU) electrodes and thermoplastic polyurethane (TPU) insulation based on commercially available multimaterial fused deposition modeling (FDM). This metamaterial capacitive sensor array is unaffected by a uniaxial stretch of up to 21.6% and remains capable of detecting normal forces. The sensor array structure possesses a negative Poisson's ratio which is desirable for improving compliance and conformability to adhered expanding surfaces. Consequently, normal force‐distribution and proximity detection capabilities on curved deforming surfaces are demonstrated on a soft universal jamming gripper for measuring gripping forces and identifying object shapes. Conformal force‐sensing joint wearable on a human elbow with an individualized Poisson's ratio is explored as another application. The possibility of programming Poisson's ratio of a metamaterial capacitive sensing array opens new avenues for potential sensing applications into soft robotics and personalized wearables.

3D printing of polycaprolactone-based composites with diversely tunable mechanical gradients via multi-material fused deposition modeling

The developed multi-material fused deposition modeling (m-FDM) 3D printing approach was proposed to fabricate functionally gradient composites (FGCs) with diversely tunable mechanical gradients. The mechanical properties of the m-FDM 3D printed FGCs were studied as a whole part, including the interlaminar shear strength (ILSS), the storage modulus, and the tensile strength. The interlaminar shear testing results convinced that the loading direction plays a crucial importance in determining the overall mechanical strength. Furthermore, the FGCs with different linear continuous gradients of filler content were prepared to examine the relationship between structures and properties of the FGCs. In addition, the porosity of the m-FDM 3D printed parts was also presented to demonstrate the mechanism behind the effect of the gradient of filler content on the whole mechanical properties. Finally, a potential application as the intermediated layers between two different materials to prevent warping and spalling when heating and achieve the optimal effect of the heat and stress transfer simultaneously. The present study elaborates on the relationship between structures and properties of FGCs, which also helps to establish a theoretical foundation of the practical applications in diverse fields.

Hybrid energy storage system design for mobile multi-material fused deposition modeling

Fused deposition modeling (FDM) is suitable for various mobile occasions due to its significant advantages, including a relatively low cost, high reliability, comfortable mobility, and low energy consumption. Nevertheless, limited by the energy density and power density of the mobile energy storage system, the printing service time and health status of the present FDM printer leave much to be desired. In this work, we derive the first survey on energy analysis of a mobile multi-material FDM by separating a full printing cycle into different operating phases, of which the individual energy consumption is analyzed. In consideration of the switching between materials with different melting temperatures, which might require significantly varying power inputs, a hybrid energy storage system consisting of both a battery and a supercapacitor is developed. In addition, by governing work mode switching based on the prediction of power changes, an energy management strategy is finally realized to meet the design requirements.

Fabrication of 3D-Printed Biodegradable Porous Scaffolds Combining Multi-Material Fused Deposition Modeling and Supercritical CO2 Techniques.

The fabrication of porous materials for tissue engineering applications in a straightforward manner is still a current challenge. Herein, by combining the advantages of two conventional methodologies with additive manufacturing, well-defined objects with internal and external porosity were produced. First of all, multi-material fused deposition modeling (FDM) allowed us to prepare structures combining poly (ε-caprolactone) (PCL) and poly (lactic acid) (PLA), thus enabling to finely tune the final mechanical properties of the printed part with modulus and strain at break varying from values observed for pure PCL (modulus 200 MPa, strain at break 1700%) and PLA (modulus 1.2 GPa and strain at break 5–7%). More interestingly, supercritical CO2 (SCCO2) as well as the breath figures mechanism (BFs) were additionally employed to produce internal (pore diameters 80–300 µm) and external pores (with sizes ranging between 2 and 12 μm) exclusively in those areas where PCL is present. This strategy will offer unique possibilities to fabricate intricate structures combining the advantages of additive manufacturing (AM) in terms of flexibility and versatility and those provided by the SCCO2 and BFs to finely tune the formation of porous structures.

Highly Sensitive and Wearable Liquid Metal-Based Pressure Sensor for Health Monitoring Applications: Integration of a 3D-Printed Microbump Array with the Microchannel.

Wearable pressure sensors capable of sensitive, precise, and continuous measurement of physiological and physical signals have great potential for the monitoring of health status and the early diagnosis of diseases. This work introduces a 3D-printed rigid microbump-integrated liquid metal-based soft pressure sensor (3D-BLiPS) for wearable and health-monitoring applications. Using a 3D-printed master mold based on multimaterial fused deposition modeling, the fabrication of a liquid metal microchannel and the integration of a rigid microbump array above the microchannel are achieved in a one-step, direct process. The microbump array enhances the sensitivity of the pressure sensor (0.158 kPa-1 ) by locally concentrating the deformation of the microchannel with negligible hysteresis and a stable signal response under cyclic loading. The 3D-BLiPS also demonstrates excellent robustness to 10 000 cycles of multidirectional stretching/bending, changes in temperature, and immersion in water. Finally, these characteristics are suitable for a wide range of applications in health monitoring systems, including a wristband for the continuous monitoring of the epidermal pulse rate for cuffless blood pressure estimation and a wireless wearable device for the monitoring of body pressure using a multiple pressure sensor array for the prevention of pressure ulcers.

Multi-material fused deposition modelling for integration of interdigital dielectric sensors into carbon fibre composite tooling for in process cure monitoring

This study introduces the concept of printing two thermoplastic materials in a single 3D Printing process – one conductive the other non-conductive – to form interdigital sensor structures for Dielectric Analysis in mould tools for cure monitoring of the epoxy matrix during the Carbon Fibre Reinforced Polymer manufacturing process. This low-cost method would allow for reduced assembly and ease of sensor placement directly from Computed Aided Design, whilst using an accessible technology.The results obtained showed a cure point can be identified in accordance with the epoxy specifications, via integration of interdigital sensors manufactured using conductive composite PolyLactic Acid with multi-material Fused Deposition Modelling.