Thermal Inkjet Technology Research Articles

A Low‐Binder‐Content Ink System for 3D Printing High‐Density and Small Feature Size 316L Stainless Steel Parts

Binder ink system is the backbone of binder jet 3D printing (BJ‐3DP) technology. Compared with metal injection molding (MIM), BJ‐3DP needs much less amount of binder, which means less exhaust gas generation during the debinding process and more environmental friendliness. More than that, low content of binder is also supposed to benefit the structure properties of the printed metal parts. Herein, an ultralow‐binder‐content ethanol–water–PVP ink system is demonstrated for the BJ‐3DP 316 L stainless steel parts by applying thermal bubble inkjet technology. The PVP binder concentration is as low as 80 mg mL−1, which can achieve an ultralow solid content of 0.2 wt% in the printed green part. The two‐component solution with water and ethanol provides not only the rheology property adjustment freedom for the ink jetting and infiltration in the metal powders, but also the two boiling points for the step‐by‐step capillary bridge formation process. By applying the low‐binder‐content ink, the fully densified 316 L stainless steel parts after sintering can obtain the relative density up to 99.4%, Vickers hardness up to 185 HV, tensile strength up to 542 MPa, 25% elongation at break, and feature size as small as 200 μm.

Research on Thermal Inkjet Technology Based on CFD

In this paper, a thermal inkjet printing simulation model is established in the CFD simulation platform, and the influence of inkjet driver parameters and ink physical parameters on the printing process is studied by numerical simulation. The evaporation-condensation model is coupled with the VOF multiphase flow model in Fluent software to establish a thermal inkjet printing process simulation model. Based on the orthogonal test method, we investigate the influence of fluid physical parameters (ink viscosity, surface tension) and inkjet driver parameters (heater temperature value) on droplet formation by changing the physical parameters of the material and the boundary conditions of the model. Through the comparison of the results, exploring the adjustment rules of thermal inkjet technology and obtaining the optimal combination of material and process parameters for high-quality ink drop formation.

Thin-Film MEMS Resistors with Enhanced Lifetime for Thermal Inkjet.

In this paper, the failure mechanisms of the thermal inkjet thin-film resistors are recognized. Additionally, designs of resistors to overcome these mechanisms are suggested and tested by simulation and experiment. The resulting resistors are shown to have improved lifetimes, spanning an order of magnitude up to 2 × 109 pulses. The thermal failure mechanisms were defined according to the electric field magnitude in three critical points—the resistor center, the resistor–conductor edge, and the resistor thermal “hot spots”. Lowering the thermal gradients between these points will lead to the improved lifetime of the resistors. Using MATLAB PDE simulations, various resistors shapes, with different electric field ratios in the hot spots, were designed and manufactured on an 8″ silicon wafer. A series of lifetime experiments were conducted on the resistors, and a strong relation between the shape and the lifetime of the resistor was found. These results have immediate ramifications regarding the different printing apparatuses which function with thermal inkjet technology, allowing the commercial production of larger thermal printheads with high MTBF rate. Such heads may fit fast and large 3D printers.

Highly stretchable hydrogels for sensitive pressure sensor and programmable surface patterning by thermal bubble inkjet technology

AbstractHydrogels with tough strength, programmable deformation are crucial for their practical applications. In this work, we reported the preparation and the programmable shape deformations of highly stretchable hydrogel. The graphene oxide/polyacrylamide/sodium alginate composite hydrogel was prepared, its microstructure and mechanical properties were studied. An aqueous calcium solution was selectively printed onto the hydrogel surfaces using an inkjet printer, resulting in programmable deformation of the composite hydrogel by creating regions of swelling/deswelling when subjected to external stimulations. Next, we fabricated a pressure‐capacitance hydrogel sensor to demonstrate its application. Furthermore, the deformation rate and extent of the hydrogels can be controlled by adjusting the printing pattern position, number, length, and calcium solution concentration. Finally, several complex 2D and 3D shapes were fabricated by printing appropriate patterns on one or both surfaces of the hydrogel sheets.

Retraction: “Numerical study of a bubble driven micromixer based on thermal inkjet technology” [Phys. Fluids 31, 062006 (2019)

Retraction: “Numerical study of a bubble driven micromixer based on thermal inkjet technology” [Phys. Fluids 31, 062006 (2019)

3D printing of ceramics and graphene circuits-on-ceramics by thermal bubble inkjet technology and high temperature sintering

Alumina ceramics and graphene circuits-on-ceramics were 3D printed using inkjet technology. Water-based binders for ceramics and graphene oxide inks were prepared and jetted through thermal inkjet printhead. To increase the density of the 3D printed ceramics, two steps sintering and one step infiltration were performed. The sintering temperature dependent structure properties of the printed ceramics were systematically studied. The 3D printed α-Al2O3 ceramic sintered at 1600 °C for 2 h has achieved maximum density of 95.2%, volume shrinkage rate of 32%, Vickers hardness of 291.6 Hv, surface roughness of 3.7 μm, and maximum compression strength and flexural strength of 89 MPa and 49.4 MPa, respectively. The average adhesion of reduced graphene oxide (rGO) to 3D printed α-Al2O3 ceramic is 7.5 N/m. The printed graphene circuits-on-ceramics has achieved conductivity of 5.34 × 102 S m−1 after annealing at 600 °C in nitrogen atmosphere.

Numerical study of a bubble driven micromixer based on thermal inkjet technology

The Editor and publisher have retracted “Numerical study of a bubble driven micromixer based on thermal inkjet technology” Phys. Fluids 31, 062006 (2019)]. Due to a legal issue related to the publication of work covered under a confidentiality agreement, the electronic version of the paper has been removed from the website.

Modeling thermal inkjet and cell printing process using modified pseudopotential and thermal lattice Boltzmann methods

Pseudopotential lattice Boltzmann methods (LBMs) can simulate a phase transition in high-density ratio multiphase flow systems. If coupled with thermal LBMs through equation of state, they can be used to study instantaneous phase transition phenomena with a high-temperature gradient where only one set of formulations in an LBM system can handle liquid, vapor, phase transition, and heat transport. However, at lower temperatures an unrealistic spurious current at the interface introduces instability and limits its application in real flow system. In this study, we proposed new modifications to the LBM system to minimize a spurious current which enables us to study nucleation dynamic at room temperature. To demonstrate the capabilities of this approach, the thermal ejection process is modeled as one example of a complex flow system. In an inkjet printer, a thermal pulse instantly heats up the liquid in a microfluidic chamber and nucleates bubble vapor providing the pressure pulse necessary to eject droplets at high speed. Our modified method can present a more realistic model of the explosive vaporization process since it can also capture a high-temperature/density gradient at nucleation region. Thermal inkjet technology has been successfully applied for printing cells, but cells are susceptible to mechanical damage or death as they squeeze out of the nozzle head. To study cell deformation, a spring network model, representing cells, is connected to the LBM through the immersed boundary method. Looking into strain and stress distribution of a cell membrane at its most deformed state, it is found that a high stretching rate effectively increases the rupture tension. In other words, membrane deformation energy is released through creation of multiple smaller nanopores rather than big pores. Overall, concurrently simulating multiphase flow, phase transition, heat transfer, and cell deformation in one unified LB platform, we are able to provide a better insight into the bubble dynamic and cell mechanical damage during the printing process.

Colorimetry as Quality Control Tool for Individual Inkjet-Printed Pediatric Formulations.

Printing technologies were recently introduced to the pharmaceutical field for manufacturing of drug delivery systems. Printing allows ondemand manufacturing of flexible pharmaceutical doses in a personalized manner, which is critical for a successful and safe treatment of patient populations with specific needs, such as children and the elderly, and patients facing multimorbidity. Printing of pharmaceuticals as technique generates new demands on the quality control procedures. For example, rapid quality control is needed as the printing can be done on demand and at the point of care. This study evaluated the potential use of a handheld colorimetry device for quality control of printed doses of vitamin Bs on edible rice and sugar substrates. The structural features of the substrates with and without ink were also compared. A multicomponent ink formulation with vitamin B1, B2, B3, and B6 was developed. Doses (4cm2) were prepared by applying 1-10 layers of yellow ink onto the white substrates using thermal inkjet technology. The colorimetric method was seen to be viable in detecting doses up to the 5th and 6th printed layers until color saturation of the yellow color parameter (b*) was observed on the substrates. Liquid chromatography mass spectrometry was used as a reference method for the colorimetry measurements plotted against the number of printed layers. It was concluded that colorimetry could be used as a quality control tool for detection of different doses. However, optimization of the color addition needs to be done to avoid color saturation within the planned dose interval.

Growth-Inhibitory Effect of Chemotherapeutic Drugs Dispensed by Inkjet Bioprinting on Cancer and Non-Cancer Cells

Thermal inkjet technology has long been used in the printing industry, but little has been studied on the benefits that it can provide to the drug-screening field. The objective of the work reported here was a proof of concept of using a modified inkjet printer to have a more accessible and miniature cellomic anticancer drug-screening platform. The authors' previous findings have shown that inkjet-based screening can reliably create isolated arrays of spots of living cells and antibiotics at low volume (180 pl) and high throughput (213 spots/sec) [J. I. Rodríguez-Dévora, B. Zhang, D. Reyna, Z. D. Shi, and T. Xu, “High throughput miniature drug-screening platform using bioprinting technology,” Biofabrication 4, 035001 (2012)]. The methodology of the work reported here included using a modified office inkjet printing device; the authors studied the inhibitory effects of dichloroacetate sodium (DCA) over hepatocellular carcinoma (HepG2) and epithelial cells (EpC). A DCA drug concentration gradient was printed over cell cultures to evaluate the drug's cytotoxic effect. Half maximal and ninety percent inhibitory concentrations (IC50, IC90) were obtained from the dose–response curves and compared with concentrations obtained using the traditional micropipetting technique. The resulting inhibitory concentration values obtained by both dispensing techniques fall within the millimolar range. The significance of these finding is that the proposed screening platform closely mimics the traditional screening outcome at a miniaturized volume rate, thus downsizing the screening process from traditional sub-microliter to nano- or even picoliter range. Inkjet technology shows promise in miniaturizing and expediting the drug-screening process. This platform can be used to asses a preliminary dose–response curve in order to improve the treatment modalities using the patient's limited supply of biopsied cells toward personalized medicine. © 2016 Society for Imaging Science and Technology.

Growth-Inhibitory Effect of Chemotherapeutic Drugs Dispensed by Inkjet Bioprinting on Cancer and Non-Cancer Cells

Thermal inkjet technology has long been used in the printing industry, but little has been studied on the benefits that it can provide to the drug-screening field. The objective of the work reported here was a proof of concept of using a modified inkjet printer to have a more accessible and miniature cellomic anticancer drug-screening platform. The authors’ previous findings have shown that inkjet-based screening can reliably create isolated arrays of spots of living cells and antibiotics at low volume (180 pl) and high throughput (213 spots/sec) [J. I. Rodríguez-Dévora, B. Zhang, D. Reyna, Z. D. Shi, and T. Xu, “High throughput miniature drug-screening platform using bioprinting technology,” Biofabrication 4, 035001 (2012)]. The methodology of the work reported here included using a modified office inkjet printing device; the authors studied the inhibitory effects of dichloroacetate sodium (DCA) over hepatocellular carcinoma (HepG2) and epithelial cells (EpC). A DCA drug concentration gradient was printed over cell cultures to evaluate the drug’s cytotoxic effect. Half maximal and ninety percent inhibitory concentrations (IC50, IC90) were obtained from the dose‐response curves and compared with concentrations obtained using the traditional micropipetting technique. The resulting inhibitory concentration values obtained by both dispensing techniques fall within the millimolar range. The significance of these finding is that the proposed screening platform closely mimics the traditional screening outcome at a miniaturized volume rate, thus downsizing the screening process from traditional sub-microliter to nano- or even picoliter range. Inkjet technology shows promise in miniaturizing and expediting the drug-screening process. This platform can be used to asses a preliminary dose‐response curve in order to improve the treatment modalities using the patient’s limited supply of biopsied cells toward personalized medicine.

REMOVED: An adaptive mesh refinement based flow simulation for free-surfaces in thermal inkjet technology

Abstract The microscopic multiphase flows of thermal inkjet (TIJ) devices usually involve a constantly changing liquid–gas interface. Often the curvature of the interface can become too high at some localized positions to be accurately resolved using a conventional static computational grid. A good solution to such challenging problem is to use the Adaptive-Mesh-Refinement (AMR) method, since AMR technique can concentrate the computational effort in the regions where it is needed most. In recent years, an open-source AMR code, Gerris , has been extensively used and benchmarked for a large variety of surface-tension dominated flows. However, the code cannot be directly used to model the TIJ process due to the lack of bubble dynamics and contact angle model for solid boundaries in the code. Therefore in the paper, we propose the following new approaches to model the TIJ flows and implement these algorithms in Gerris : (1) the vapor bubble is treated as an empty cavity so that its complex behavior of the vapor bubble after the bubble nucleation can be modeled using the adiabatic gas expansion and compression; (2) a height-function method based contact angle model is developed and implemented on the embedded solid surfaces. The new code has been verified and validated through a series of numerical examples and experimental tests. The proposed AMR method and the simulation code can be used in a broad range of applications in TIJ technology as well as multiphase flows of microfluidics.

Highly Sensitive Filter Paper Substrate for SERS Trace Explosives Detection

We report on a novel and extremely low-cost surface-enhanced Raman spectroscopy (SERS) substrate fabricated depositing gold nanoparticles on common lab filter paper using thermal inkjet technology. The paper-based substrate combines all advantages of other plasmonic structures fabricated by more elaborate techniques with the dynamic flexibility given by the inherent nature of the paper for an efficient sample collection, robustness, and stability. We describe the fabrication, characterization, and SERS activity of our substrate using 2,4,6-trinitrotoluene, 2,4-dinitrotoluene, and 1,3,5-trinitrobenzene as analytes. The paper-based SERS substrates presented a high sensitivity and excellent reproducibility for analytes employed, demonstrating a direct application in forensic science and homeland security.

Comparison of novel and conventional calibration techniques for the analysis of urine samples using plasma source mass spectrometry combined with a new dual-drop-on-demand aerosol generator

The accuracy and precision of the analytical data from the analysis of liquid samples with high matrix load often suffer from a compromised performance of the sample introduction system. This is especially significant in the case of miniaturized, pneumatic low flow nebulizers. Alternative low-flow sampling devices based on different operating principles are imperative to overcome this drawback. The superior performance of such an alternative liquid sample introduction system for ICP-MS, the drop-on-demand (DOD) aerosol generator based on thermal inkjet technology, was recently outlined by the same group for the analysis of aqueous standard solutions. Current improvements of the system now allow for the independent operation of two sampling nozzles, which expands the system capabilities to independently dosing two liquids simultaneously into the carrier gas stream of an ICP-MS. The applicability of the proposed dual-DOD (dDOD) ICP-MS method to the analysis of real urine samples is outlined. Its susceptibility to matrix effects was studied through 2-dimensional ion distributions within the ICP for different matrices. A new calibration strategy for ICP-MS based on the dosing frequencies of the dDOD (dosing frequency-based calibration, DFC) and its application to trace metal analysis in micro-volumes of real samples with high matrix content are presented. Using this method Li, Sr, Mo, Sb and Cs were accurately determined in the concentration range of 8–122 μg L−1 in urine reference material. The advantages of the DFC, e.g. minimum sample and analysis time consumption, are outlined and the quality of the achievable results with respect to accuracy and precision is critically discussed. All analytical data are compared to those obtained with a conventional MicroMist nebulization system in combination with ICP-MS using classic calibration procedures.

Thermal inkjet printing for precision histological staining

Inkjet printing techniques may allow enhanced analysis of tissues. When the tissue available for processing is limited, for example, the amount of information obtained could be increased if different stains could be applied to discrete areas of the same tissue sections. In addition, it may be more desirable to stain an intact tissue rather than sections of tissue. Currently, there are very few methods by which many different stains can be applied in a controlled manner to a single section and/or single block of tissue. This paper presents a liquid deposition system, based on thermal inkjet technology, capable of precisely applying histological processing liquids to form high precision patterns at desired locations on both fixed tissues and cell monolayers. Four experiments were conducted to show the potential of single-drop reagent application, using aniline blue, toluidine blue, fluorescent probes, and an immunofluorescence antibody to create different patterns. Tissue type was shown to affect the overall quality of staining. The flexibility, resolution, and precision of this system have the potential to enable the formulation of new staining techniques to maximize the amount of information gleaned from a given tissue sample.

Preparation of TNT, RDX and Ammonium Nitrate Standards on Gold-on-Silicon Surfaces by Thermal Inkjet Technology

This research examines the surface contamination properties, trace sample preparation methodologies, detection systems response and generation of explosive contamination standards for trace detection systems. Homogeneous and reproducible sample preparation is relevant for trace detection of chemical threats, such as warfare agents, highly energetic materials (HEM) and toxic industrial chemicals. The objective of this research was to develop a technology capable of producing samples and standards of HEM with controlled size and distribution on a substrate to generate specimens that would reproduce real contamination conditions. The research activities included (1) a study of the properties of particles generated by two deposition techniques: sample smearing deposition and inkjet deposition, on gold-coated silicon, glass and stainless steel substrates; (2) characterization of composition, distribution and adhesion characteristics of deposits; (3) evaluation of accuracy and reproducibility for depositing neat highly energetic materials such as TNT, RDX and ammonium nitrate; (4) a study of HEM-surface interactions using FTIR-RAIRS; and (5) establishment of protocols for validation of surface concentration using destructive methods such as HPLC.

Thermal Inkjet Application in the Preparation of Oral Dosage Forms: Dispensing of Prednisolone Solutions and Polymorphic Characterization by Solid-State Spectroscopic Techniques

The utility of thermal inkjet (TIJ) technology for preparing solid dosage forms of drugs was examined. Solutions of prednisolone in a solvent mixture of ethanol, water, and glycerol (80/17/3 by volume) were dispensed onto poly(tetrafluoroethylene)-coated fiberglass films using TIJ cartridges and a personal printer and using a micropipette for comparison. The post-dried, TIJ-dispensed samples were shown to contain a mixture of prednisolone Forms I and III based on PXRD analyses that were confirmed by Raman analyses. The starting commercial material was determined to be Form I. Samples prepared by dispensing the solution from a micropipette initially showed only Form I; subsequent Raman mapping of these samples revealed the presence of two polymorphs. Raman mapping of the TIJ-dispensed samples also showed both polymorphs. The results indicate that the solvent mixture used in the dispensing solution combined with the thermal treatment of the samples after dispensing were likely the primary reason for the generation of the two polymorphs. The advantages of using a multidisciplinary approach to characterize drug delivery systems are demonstrated using solid state mapping techniques. Both PXRD and Raman spectroscopy were needed to fully characterize the samples. Finally, this report clarifies prednisolone's polymorphic nomenclature existent in the scientific literature. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:2619–2636, 2008

Thermal Ink Jet System to Enable Non-Traditional Applications

Thermal Inkjet (TIJ) drop-on-demand printheads have traditionally been limited to the jetting of colorant in imaging and marking applications. The complexity and size of the ink delivery systems and printheads as well as the generally closed firmware employed in consumer TIJ printers have dissuaded most researchers from attempting to use TIJ in the various emerging digital fabrication applications. This dearth of public activity has contributed to the wide perception that TIJ is not appropriate for applications that involve the jetting of non-aqueous or thermallysensitive fluids.In this talk, I will describe recent developments in noncolorant jetting applications using thermal inkjet technology. Methods to enable user control over jetting parameters (pulse widths, voltages, temperatures, number of nozzles) and to integrate these TIJ-based capabilities into larger systems are discussed. Methods to enable users to use a small (less than 150 μL) quantity of fluid to jet a large range of drop weights (from 2 pL to 220 pL) are also discussed.In addition to describing these recent developments in TIJ capability, I will describe various applications that have been enabled by this capability and present theory and empirical data to show that TIJ is indeed capable of the ejection of non-aqueous fluids and thermally-sensitive materials (including enzymes and other proteins) without significant or meaningful degradation to these materials.

Interfacial reactions and phase equilibria in the Al-Cu/Ta systems

Thermal inkjet technology is in widespread use for color printers. In the roofshooter thermal inkjet printhead, tantalum is often used as the diffusion barrier between the gold and the conduction layers, Al, Cu, and Al-Cu. This study investigated the contact stabilities of Al/Ta, Cu/Ta, and Al-Cu/Ta systems using the reaction couple technique. The couples were annealed in a furnace at 600°C, 750°C, 900°C, 1000°C, and 1200°C for various lengths of time. One reaction layer, the Al3Ta phase, was formed at the interface in the Al/Ta and Al-Cu/Ta couples heat treated at 750°C, 900°C, and 1000°C. No Cu is observed in the Al3Ta phase even in the Al-Cu/Ta couples; however, the reaction couples with Al-Cu have slower reaction rates. For the Al/Ta reaction couples annealed at 600°C and Cu/Ta couples annealed at 750°C, 900°C, 1000°C, and 1200°C, no noticeable interfacial reaction was observed. It was concluded that the contacts were very stable and Ta was a very good barrier layer. In addition, phase equilibria studies of the Al-Ta system were carried out. The experimental results indicate that the Al2Ta phase was not stable at 850°C and higher. A revised Al-Ta phase diagram was proposed in this study.

Thermal Inkjet Technology for the Microdeposition of Biological Molecules as a Viable Route for the Realization of Biosensors

Recent progress in inkjet printing of parts of biosensors are highlighted, with particular reference to the printing of biologically active molecules. We describe a system constituted by a thermal inkjet printer, adapted to layering a bidimensional array of dots [701 × 701 dots per inch] on solid supports. The printer was used to depose a β‐galactosidase (GAL)‐containing ink on a polyester sheet, with dots obtained from 10 pL drops, each drop containing in turn 6 pg of enzyme. The activity of GAL after the preparation was determined using a colorimetric probe (Brilliant Blue FCF). The activity loss of the microdeposed enzymes was found to be around 15%, showing that the 2 µsec‐lasting thermal shock experienced by the biomolecule into the printhead nozzle affects to a lesser extent the activity of the thermal inkjet deposited enzyme. In conclusion, the most recent findings of our group in this line are depicted, and a view of possible future developments of the “biopolytronics” field is outlined.