Piezoelectric Printhead Research Articles

MAGIC matrices: freeform bioprinting materials to support complex and reproducible organoid morphogenesis.

Organoids are powerful models of tissue physiology, yet their applications remain limited due to their relatively simple morphology and high organoid-to-organoid structural variability. To address these limitations we developed a soft, composite yield-stress extracellular matrix that supports optimal organoid morphogenesis following freeform 3D bioprinting of cell slurries at tissue-like densities. The material is designed with two temperature regimes: at 4 °C it exhibits reversible yield-stress behavior to support long printing times without compromising cell viability. When transferred to cell culture at 37 °C, the material cross-links and exhibits similar viscoelasticity and plasticity to basement membrane extracts such as Matrigel. We first characterize the rheological properties of MAGIC matrices that optimize organoid morphogenesis, including low stiffness and high stress relaxation. Next, we combine this material with a custom piezoelectric printhead that allows more reproducible and robust self-organization from uniform and spatially organized tissue "seeds." We apply MAGIC matrix bioprinting for high-throughput generation of intestinal, mammary, vascular, salivary gland, and brain organoid arrays that are structurally similar to those grown in pure Matrigel, but exhibit dramatically improved homogeneity in organoid size, shape, maturation time, and efficiency of morphogenesis. The flexibility of this method and material enabled fabrication of fully 3D microphysiological systems, including perfusable organoid tubes that experience cyclic 3D strain in response to pressurization. Furthermore, the reproducibility of organoid structure increased the statistical power of a drug response assay by up to 8 orders-of-magnitude for a given number of comparisons. Combined, these advances lay the foundation for the efficient fabrication of complex tissue morphologies by canalizing their self-organization in both space and time.

A 3D‐Printed Printhead: Custom Inkjet Dispenser for Medium Viscosity Fluids

Inkjet is a versatile non‐contact printing technique that uses droplets of ink jetted from nozzles to print on a variety of substrates. Although some modern piezoelectric printheads support high viscosity fluids (>10 cP), they are currently expensive and may not be suited for many benchtop experiments in research environment. Here, the design, fabrication by 3D‐printing (no cleanroom processes or silicon micromachining are involved) and testing of a multi‐purpose single‐nozzle piezoelectric dispenser/printhead for medium‐viscosity fluids (10–60 cP) is reported. Custom control electronics are developed to drive the printhead. The design features a 200 μm diameter nozzle, suitable for nL drop generation with solutions containing nm sized particles, thus allowing the deposition of μm thick layers of functional inks in a single printing pass. The inkjet dispenser is first tested with glycerol solutions, resulting in drops of 1.9–3.6 nL with typical drop velocity of 0.5–1.3 m s−1. The developed piezoelectric dispensing system is then demonstrated in the printing of a two‐layer capacitive sensor, using silver nanoparticle ink (conductive ink) and a transparent encapsulant ink (dielectric ink). The reported piezoelectric dispenser design can be optimized for many research purposes, allowing the dispensing of functional chemicals, materials, and biomolecules.

Numerical study of drop dynamics for inkjet based 3D printing of pharmaceutical tablets

Interest in 3D printing has been growing rapidly especially in pharmaceutical industry due to its multiple advantages such as manufacturing versatility, personalization of medicine, scalability, and cost effectiveness. Inkjet based 3D printing gained special attention after FDA’s approval of Spritam® manufactured by Aprecia pharmaceuticals in 2015. The precision and printing efficiency of 3D printing is strongly influenced by the dynamics of ink/binder jetting, which further depends on the ink’s fluid properties. In this study, Computational Fluid Dynamics (CFD) has been utilized to study the drop formation process during inkjet-based 3D printing for piezoelectric and thermal printhead geometries using Volume of Fluid (VOF) method. To develop the CFD model commercial software ANSYS-Fluent was used. The developed CFD model was experimentally validated using drop watcher setup to record drop progression and drop velocity. During the study, water, Fujifilm model fluid, and Amitriptyline drug solutions were evaluated as the ink solutions. The drop properties such as drop volume, drop diameter, and drop velocity were examined in detail in response to change ink solution properties such as surface tension, viscosity, and density. A good agreement was observed between the experimental and simulation data for drop properties such as drop volume and drop velocity.

Droplet volume modulation based on multi-waveform superposition for drop-on-demand material jetting

The piezoelectric drop-on-demand material jetting technique is widely used in additive manufacturing due to its cost-effectiveness, high accuracy, and the ability to efficiently print a variety of materials. However, there is a conflict between the requirements related to printing productivity and printing quality, which is solved by the droplet volume modulation method. In recent years, a variety of inkjet technologies have been developed to control the droplet volume, but control was achieved only over a small range, with the ratio between the maximum and minimum volume approx. 10. In this paper, the advance droplet phenomenon was shown and its formation mechanism was determined through experiments and simulations. Based on the formation mechanism and the response characteristic of the piezoelectric printhead to the basic waveform, a droplet volume modulation method was proposed. The method was based on multi-waveform superposition and the aim was to achieve a larger volume range of droplet ejection. The experimental results have shown that the newly designed waveform results in a controllable and stable single droplet ejection in a volume range from 0.61 pl to 83.7 pl, with the ratio between the maximum and minimum volume more than 130, an order of magnitude above current levels. Hence, this work provides a new perspective for improving both the printing quality and printing productivity of additive manufacturing.

Compensated printing and characterization of the droplet on the binder migration pattern during casting sand mold 3D printing

With its unique advantages, binder jetting additive manufacturing technology has shown significant development potential in the additive manufacturing of complex casting sand mold. After droplet deposition, the permeation and migration of the liquid binder in the porous powder bed have a critical impact on the final performance of the printed sand mold. Taking the piezoelectric printhead as the research object, using Furan resin as the liquid binder and silica particles for the powder bed, the effect of binder content on the dimensional accuracy and mechanical properties of the formed sand mold parts was discussed. Several samples were printed with different volumes of droplets, and the droplet diffusion mode, dimensional accuracy, mechanical properties, and formability were measured, respectively. These indicators were quantified based on the different binder saturation, by comprehensively considering the correlation between the indicators. The methods of grayscale printing and layer thickness compensation are given to improve the product quality. The results show that a more extensive liquid saturation produces better strength and formability with the tradeoff of a significant increase in dimension error. However, by independently adjusting the droplet amount of the liquid binder at each printhead, the desired dimension inaccuracy, strength, and formability can be achieved at each precise place. The future application can be implemented in the binder jetting of precision casting sand mold 3D printing to accelerate its industrial development.

Additive manufacturing of low-temperature co-fired ceramic substrates and surface conductors based on material jetting

Integrated manufacturing of ceramic substrates and surface conductors using 3D material jetting (MJ) technology is a novel additive manufacturing route for low-temperature co-fired ceramics (LTCC). This study evaluates the rheological and jetting properties of LTCC nanoceramic inks with varying solids contents. Ceramic inks with 35 % solid content were found to be the optimal choice with high particle concentration and Ohnesorge numbers (Oh) below 1. The fabrication process used two piezoelectric printheads to inject nanoceramic ink and nanosilver ink to create a ceramic substrate and a surface interdigital electrode (IDE). The substrate sintering shrinkage was 21.5 % and the surface IDE co-fired at the same shrinkage rate as the substrate thus ensuring all electrode pattern details. The electrode conductors demonstrated effective line widths of up to 0.21 mm. Microscopic characterisation of the interface between silver and substrate using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) confirmed the absence of significant elemental diffusion, and X-ray diffraction spectroscopy (XRD) results demonstrate that there is no second-phase generation, thus ensuring the effectiveness of the silver electrode. The ceramic substrates exhibit good thermal stability below 400 ℃ and have a coefficient of thermal expansion (∼ 4.1 ppm/℃) similar to that of silicon, indicating reliability in packaging. A microstrip patch antenna with the design frequency at 9–11 GHz was made through the same MJ procedure, which was experimentally measured to have a resonant frequency of 10.1 GHz, an S11 measurement of −24.6 dB, a simulated radiation efficiency of 88.01 %, and a high gain of up to 7.52 dB. Finally, a curved LTCC substrate with a radius of curvature of 50 mm and curved circuits was successfully fabricated using MJ technology. Interestingly, the curvature of the substrate maintained its original shape both before and after the sintering process, and the serpentine conductor pattern exhibited synchronous contraction, which implies the potential for developing a conformal LTCC utilizing MJ technology.

Efficient Creation of Jettability Diagrams Using Active Machine Learning.

The ability to jet a wide variety of materials consistently from print heads remains a key technical challenge for inkjet-based additive manufacturing processes. Drop watching is the most direct method for testing new inks and print head designs but such experiments are also resource consuming. In this work, a data-efficient machine learning technique called active learning is used to construct detailed jettability diagrams that identify complex regions corresponding to "no jetting," "jetting," and "desired jetting," rather than only individually sampled points. Crucially, our active learning method has resolved challenges with model selection that previously limited the accuracy of active learning in practical settings with very small experimental budgets. In addition, the key "desired jetting" zone may be quite small which is a challenge for initializing active learning. We leverage the physical intuition that the "desired jetting" zone tends to exist between the "jetting" and "no jetting" zone, to improve the performance of this highly imbalanced classification problem by performing two binary classifications in sequence. The first binary classification aims to map out the "jetting" zone versus the "no jetting" zone, while the second binary classification targets identifying the "desired jetting" zone with primary drops only. Our experiments use a stroboscopic drop watcher to visualize the jetting behavior of two fluids from a piezoelectric print head with different jetting waveforms. The results obtained from active learning were compared to a grid search method, which involves running more than 200 experiments for each fluid. The active learning method significantly reduces the number of experiments by 80% while achieving a test accuracy of more than 95% in the "jetting" zone prediction for the test fluids. The ability to construct these jettability diagrams will further accelerate new ink and print head developments.

Numerical Research on the Effects of Process Parameters on Microdroplet Jetting Characteristics by Piezoelectric Printhead

The precision and consistency of the microdroplet jetting procedure are crucial for the casting sand mold’s performance during binder injection. The generation and jetting of microdroplets in piezoelectric printheads were examined in this study in relation to changes in specific jetting process parameters. Using finite element analysis and a simplified physical model of a microdroplet jetting device, an electromechanically coupled model of a microdroplet jetting device was created in order to study the characteristics of microdroplet jetting. A volume-of-fluid model was also created in order to study the microdroplet jetting process and perform repeatability tests. The effects of altering nozzle radius, actuation pulse width, intake velocity, and fluid viscosity on microdroplet jetting properties were then investigated using the models. We were able to control the development of satellite droplets thanks to the knowledge we gained about how each process parameter affected droplet status. This study demonstrates how the radius of the nozzle and the pulse width of the piezoelectric actuation signal have a significant impact on the jetting properties of piezoelectric printheads and the production of microdroplets. The quantitative correlations between process factors and jetting characteristics can be used to optimize microdroplet production and reduce droplet size. Finally, this study will help create control systems for microdroplet jetting operations and enhance the precision of 3D printed casting sand molds.

Waveform Design Method for Piezoelectric Print-Head Based on Iterative Learning and Equivalent Circuit Model

Piezoelectric print-heads (PPHs) are used with a variety of fluid materials with specific functions. Thus, the volume flow rate of the fluid at the nozzle determines the formation process of droplets, which is used to design the drive waveform of the PPH, control the volume flow rate at the nozzle, and effectively improve droplet deposition quality. In this study, based on the iterative learning and the equivalent circuit model of the PPHs, we proposed a waveform design method to control the volume flow rate at the nozzle. Experimental results show that the proposed method can accurately control the volume flow of the fluid at the nozzle. To verify the practical application value of the proposed method, we designed two drive waveforms to suppress residual vibration and produce smaller droplets. The results are exceptional, indicating that the proposed method has good practical application value.

Piezoelectric Drop-on-Demand Inkjet Printing with Ultra-High Droplet Velocity.

Improving droplet velocity as much as possible is considered as the key to improving both printing speed and printing distance of the piezoelectric drop-on-demand inkjet printing technology. There are 3 tough and contradictory issues that need to be addressed simultaneously, namely, the actuation pressure of the piezoelectric printhead, satellite droplets, and the air resistance, which seems almost impossible to achieve with classical methods. Herein, a novel solution is introduced. By modulating the positive crosstalk effect inside and outside the printhead, self-tuning can be achieved, including self-reinforcing of the actuation pressure, self-restraining of satellite droplets, and self-weakening of the air resistance, thereby greatly improving droplet velocity. Based on these mechanisms, waveform design methods for different inks and printheads are investigated. The results demonstrate that monodisperse droplet jetting with a maximum velocity of 27.53 m/s can be achieved, reaching 3 to 5 times that of the classical method (5 to 8 m/s). Correspondingly, the printing speed and distance can be simultaneously increased by almost 10 times, demonstrating an ability of direct printing on irregular surface. Meanwhile, the compatibility of ink materials is expanded, as the Ohnesorge number and the viscosity of printable inks for the printhead used are increased from 0.36-0.72 to 0.03-1.18 and from 10-12 cp to 1-40.3 cp, respectively, even breaking the traditional limitations of the piezoelectric printing technology (Ohnesorge number of 0.1 to 1; viscosity of 1 to 25 cp). All the above provide a new perspective for improving droplet velocity and may even offer a game-changing choice for expanding the boundaries of the piezoelectric drop-on-demand inkjet printing technology.

Actuation waveform optimization via multi-pulse crosstalk modulation for stable ultra-high frequency piezoelectric drop-on-demand printing

Piezoelectric drop-on-demand inkjet printing is a widely used additive manufacturing technology, in which droplets are ejected from a piezoelectric printhead under certain actuation waveforms to form three-dimensional structures. The crosstalk generated by high- frequency multi-pulse actuation waveforms in the piezoelectric printhead has always been considered detrimental and needs to be suppressed, since it significantly limits the improvements of the working frequency of piezoelectric inkjet printing. Herein, the high- frequency multi-pulse crosstalk behaviors in a single nozzle of a piezoelectric printhead were investigated experimentally and numerically. The phenomenon of the droplet jetting state oscillating regularly with the increase of the pulse frequency was found to be controlled by the constructive/destructive interference mechanism of the multi-pulse crosstalk. The maximum frequency for stable droplet jetting could be obtained under the optimal constructive interference. Based on this mechanism, an actuation waveform optimization method via multi-pulse crosstalk modulation for stable ultra-high frequency piezoelectric drop-on-demand printing was explored. The results demonstrated that, under the optimized actuation waveform, the printhead used in this paper, which with a nominal working frequency less than 20 kHz, could achieve controllable and stable droplet jetting even at working frequencies up to 200 kHz. In other words, the jetting frequency was increased by more than 10 times. This work provides a new perspective for improving the efficiency of additive manufacturing processes based on the piezoelectric inkjet printing technology.

Development of an Inkjet Setup for Printing and Monitoring Microdroplets

Inkjet printing is a digitally controlled additive technology that allows the precise deposition of droplets. Because it is additive, it enables geometries usually unattainable by other technologies. Because it is digitally controlled, its output is easily modulated, even during operation. Combined with the development of functional materials and their micrometer precision, it can be applicable in a wide range of fields beyond the traditional graphic industry, such as medical diagnosis, electronics manufacturing, and the fabrication of microlenses. In this work, a solution based on open-source hardware and software was implemented instead of choosing a commercial alternative, making the most of inkjet flexibility in terms of inks, substrates, and actuation signal. First, a piezoelectric printhead from MicroFab, driven by an ArduinoDue, was mounted in a 3D printer adapted to ensure precise movement in three dimensions. Then, a monitoring system using a USB digital microscope and a computational algorithm was integrated. Both systems combined allow the printing and measurement of microdroplets by digital regulation of a unipolar signal. Finally, based on a theoretical model and a set of experimentally collected samples, the curve that relates the unipolar signal amplitude to the size of the microdroplets was estimated with an acceptable range of prediction uncertainty.

The Evaluation and Exploration of Piezoelectric Parameter Optimization for Droplet Ejection in Binder Jet 3D Printing Drugs.

Since the first three-dimensional (3D) printed drug was approved by the Food and Drug Administration in 2015, there has been a growing interest in using binder jet 3D printing (BJ-3DP) technology for pharmaceuticals. However, most studies are still at an exploratory stage, lacking micromechanism research, such as the droplet ejection mechanism, the effect of printhead piezoelectric parameters on inkjet smoothness and preparation formability. In this study, based on the inkjet printing and observation platform, the Epson I3200-A1 piezoelectric printhead matched to the self-developed BJ-3DP was selected to analyze the droplet ejection state of self-developed ink at the microlevel with different piezoelectric pulse parameters. The results showed that there was a stable inkjet state with an inkjet pulse width of 3.5 μs, an ink supply pulse width of 4.5 μs, and a jet frequency in the range of 5000-19,000 Hz, ensuring both better droplet pattern and print accuracy, as well as high ejection efficiency. In conclusion, we performed a systematic evaluation of the inkjet behavior under different piezoelectric pulse parameters and provided a good idea and case study for the optimization of printhead piezoelectric parameters when BJ-3DP technology was used in pharmaceuticals.

Membrane resonant based droplet ejector for micro-droplet jetting

A novel membrane resonant droplet ejector (MRDE) for viscous industrial liquids is proposed in the paper. In MRDE, a vibrating nozzle is built to generate micro-droplets and the nozzle clogging could be reduced. The droplet jetting mechanism is studied by a three-dimensional (3D) lattice Boltzmann (LB) model. The effects of voltage amplitude and driving frequency on droplet volume and velocity are explored. Experimental Results show that low-viscosity water and viscous glycol could be jetted stably in parameters of 30 V/16 kHz and 60 V/20 kHz, respectively. Moreover, the droplet jetting of MRDE and in-situ observation is set up to analysis the droplet jetting characteristics. The critical thresholds for MRDE are9.340≤Re≤17.65, 3.653≤We≤8.846 and 0.014≤oh≤0.411, which has a wider printable range than traditional piezoelectric printheads. With the compact structure, MRDE is easy of integration for mass industrial applications compared with the pneumatic and needle-based ejectors.

Numerical Analysis and Optimal CFD Model Verification of Piezoelectric Inkjet Printhead

Flow dynamics accurate prediction is critical for the early-stage design and performance optimization of the piezoelectric (PZT) printhead. To achieve this, the Computational Fluid Dynamics (CFD) method has been widely used. However, for accurate fluid simulation of the PZT printhead, the optimal parameters settings still need to be clarified, which will be discussed in full in this paper. The modelling work is divided into two sub-parts, namely, a three-dimensional (3-D) modelling for the ink chamber and a two-dimensional (2-D) modelling for the nozzle-air domain. Simulations of the 3-D ink chamber were carried out firstly, thereby the transient mass flow rate of the ink outflow from the chamber could be obtained, which will be set as the inlet boundary condition of the 2-D nozzle-air simulations. To ensure accuracy and convergence of 2-D simulations, independence tests of the mesh grid and time step were performed, where the Fine level mesh density and 1e-8 s time step were identified as the optimal choice. And this combination was adopted in the transient simulations of the droplet ejection process. For the model validation purpose, an experimental test rig was developed, and comparisons between the simulations and experimental tests show a good agreement, verifying the accuracy of the developed model. In addition, to validate the feasibility of the developed model, the effect of the ink viscosity on the droplet ejection process was tested, and the results were consistent with those produced by published literature, confirming the feasibility of the CFD model developed in this paper.

Development of high-frequency and high-viscosity piezoelectric DOD print head and its jet performance

The demand for print heads with a wide range of jet viscosity and high jet frequency became evident with the development of micro-drop inkjet technology. In this paper, a new high-frequency and high-viscosity piezoelectric drop-on-demand (DOD) print head structure was proposed and manufactured. Furthermore, its reliability was confirmed via hydrodynamic and thermodynamic simulation analyses. The print head jetting performance was tested through the print head jetting performance test platform, and the effects of various waveform driving parameters on the performance were observed. The influences of dwell time, voltage amplitude, and drive frequency were considered. The results have shown that the print head jetting viscosity ranges up to 8.2 cps at room temperature, with the highest value being 98.17 cps obtained after regulating the solution viscosity and the temperature field. Moreover, the stable ejection droplet driving frequency was up to 15 kHz, confirming the good jetting stability.

Inkjet-printed HF antenna made on PET substrate

PurposeThis paper aims to study planar antenna fabrication in inkjet printing technology. It presents the technological problems connected with the effective deposition of nanoparticle ink on PET substrate via a piezoelectric printhead, as well as the parameters of the fabricated structures. Design/methodology/approachAn antenna model for HF RFID tag was prepared using the tool HyperLynx 3D EM tool on the basis of the results of preliminary studies in the field of inkjet printing. The inkjet printing process was studied by observing the parameters of drops formed by the piezoelectric printhead. The drops of nanoparticle ink were deposited on heated PET substrate which was treated and untreated. After recognizing the morphology conditions simple structures were printed and their profiles were measured. In the next step, antenna structures were printed on untreated PET using an anti-spread strategy. The morphology of the antenna element was observed and defects caused by the various drop parameters were analyzed. The impedance of fabricated antennas was measured and linked to the technological parameters in the discussion section of this paper. The influence of the ageing processes on the antenna properties was finally investigated. FindingsThe results indicate the possibility of inkjet printing the antennas on untreated PET. The antenna parameters are sufficiently repeatable, but the ink deposition technique employed leads to an increase in antenna resistance because of defects caused by the diversity of the drops parameters. The ageing processes cause a decrease in resistance, contrary to preliminary expectations. Originality/valueThis study presents the results of original empirical research connected with the technological processes operating on new nanomaterials and identifies problems that must be resolved in order to disseminate this technology. Research limitations/implicationsBecause of the research method chosen (selected printhead type, substrate, nanoparticle ink and how the technological process was conducted), this study may have limited universality. Therefore, the authors encourage the study of other kinds of equipment and antenna printing materials. Practical implicationsThis study contains the results of real technological processes that can be repeated by other researchers. The results can also be helpful in developing new improved process parameters which can be applied in other processes.

A Multi-Fidelity Model for Simulations and Sensitivity Analysis of Piezoelectric Inkjet Printheads.

The ink drop generation process in piezoelectric droplet-on-demand devices is a complex multiphysics process. A fully resolved simulation of such a system involves a coupled fluid–structure interaction approach employing both computational fluid dynamics (CFD) and computational structural mechanics (CSM) models; thus, it is computationally expensive for engineering design and analysis. In this work, a simplified lumped element model (LEM) is proposed for the simulation of piezoelectric inkjet printheads using the analogy of equivalent electrical circuits. The model’s parameters are computed from three-dimensional fluid and structural simulations, taking into account the detailed geometrical features of the inkjet printhead. Inherently, this multifidelity LEM approach is much faster in simulations of the whole inkjet printhead, while it ably captures fundamental electro-mechanical coupling effects. The approach is validated with experimental data for an existing commercial inkjet printhead with good agreement in droplet speed prediction and frequency responses. The sensitivity analysis of droplet generation conducted for the variation of ink channel geometrical parameters shows the importance of different design variables on the performance of inkjet printheads. It further illustrates the effectiveness of the proposed approach in practical engineering usage.

Study on driving waveform design process for multi-nozzle piezoelectric printhead in material-jetting 3D printing

Purpose Material-jetting (MJ) three-dimensional (3D) printing processes are competitive due to their printing resolution and printing speed. Driving waveform design of piezoelectric printhead in MJ would affect droplet formation and performance, but there are very limited studies on it besides patents and know-hows by commercial manufacturers. Therefore, in this research, the waveform design process to efficiently attain suitable parameters for a multi-nozzle piezoelectric printhead was studied. Therefore, this research aims to study the waveform design process to efficiently attain suitable parameters for a multi-nozzle piezoelectric printhead. Design/methodology/approach Ricoh’s Gen4L printhead was adopted. A high-speed camera captured pictures of jetted droplets and droplet velocity was calculated. The waveforms included single-, double- and triple-pulse trapezoidal patterns. The effects of parameters were investigated and the suitable ones were determined based on the avoidance of satellite drops and preference of higher droplet velocity. Findings In a single-pulse waveform, an increase of fill time (Tf) decreased the droplet velocity. The maximum velocity happened at the same pulse width, the sum of fill time and hold time (Tf + Th). In double- and triple-pulse, a voltage difference (Vd) above zero in the holding stage was adopted except the last pulse to avoid satellite drops. Suitable parameters for the selected resin were obtained and the time-saving design process was established. Research limitations/implications Based on the effects of parameters and observed data trends, suggested procedures to determine suitable parameters were proposed with fewer experiments. Practical implications This study has verified the feasibility of suggested design procedures on another resin. The required number of trials was reduced significantly. Originality/value This research investigated the process of driving waveform design for the multi-nozzle piezoelectric printhead. The suggested procedures of finding suitable waveform parameters can reduce experimental trials and will be applicable to other MJ 3D printers when new materials are introduced.

Development of a pilot-scale HuskyJet binder jet 3D printer for additive manufacturing of pharmaceutical tablets

This paper reports a custom-built binder jet 3D printer for pilot-scale manufacturing of pharmaceutical tablets. The printer is equipped with high-throughput piezoelectric inkjet print heads and allows direct control of several key process parameters, including the build layer thickness, amount of jetted liquid binder, and powder spreading rate. The effects of these parameters on the properties of the as-printed tablets were studied using a powder mixture of lactose monohydrate and Kollidon® VA64 (KL) and an aqueous binder containing 5% of KL. The appropriate processing windows for two different powder spreading rates were identified, and the final properties of the printed samples were explained using a dimensionless “degree of overlap” parameter which is defined as the ratio between the penetrating depth of the binder into the powder and the build layer thickness. Lastly, 10% of indomethacin was added to the powder feedstock as a model drug. Drug-loaded tablets were produced at a rate of 32 tablets/min, having an average breaking force of 9.4 kgf, a friability of 2.5%, and an average disintegration time of 8 s. These properties are comparable to commercially available tablets and represent one of the best values reported in the literature of 3D printed tablets thus far.