Inkjet Research Articles

Cost‐Effective DNA Storage System with DNA Movable Type

AbstractIn the face of exponential data growth, DNA‐based storage offers a promising solution for preserving big data. However, most existing DNA storage methods, akin to traditional block printing, require costly chemical synthesis for each individual data file, adopting a sequential, one‐time‐use synthesis approach. To overcome these limitations, a novel, cost‐effective “DNA‐movable‐type storage” system, inspired by movable type printing, is introduced. This system utilizes prefabricated DNA movable types‐short, double‐stranded DNA oligonucleotides encoding specific payload, address, and checksum data. These DNA‐MTs are enzymatically ligated/assembled into cohesive sequences, termed “DNA movable type blocks,” streamlining the assembly process with the automated BISHENG‐1 DNA‐MT inkjet printer. Using BISHENG‐1, 43.7 KB of data files are successfully printed, assembled, stored, and accurately retrieved in diverse formats (text, image, audio, and video) in vitro and in vivo, using only 350 DNA‐MTs. Notably, each DNA‐MT, synthesized once (2 OD), can be used up to 10000 times, reducing costs to $122/MB—outperforming existing DNA storage methods. This innovation circumvents the need to synthesize entire DNA sequences encoding files from scratch, offering significant cost and efficiency advantages. Furthermore, it has considerable untapped potential to advance a robust DNA storage system, better meeting the extensive data storage demands of the big‐data era.

Additively manufactured microwave sensor for glucose level detection in saliva.

In this paper, a novel realization of an ink-on-glass microwave sensor for biomedical applications is proposed. The Aerosol Jet Printing (AJP) technology is leveraged to implement a compact single-layer coplanar waveguide sensor featuring arc-shaped interdigital fingers that can accommodate a droplet of the Material-Under-Test (MUT). Such geometry provides a high sensitivity to even a very small deviation of MUT`s electrical properties when placed as a superstrate. An application towards the detection of trace amounts of glucose in saliva, which is a biomarker for diabetes, is showcased. The design and fabrication process of an exemplary sensor is discussed in detail. A circular geometry feature is introduced that helps a droplet to lie over the sensitive region due to wettability difference of glass substrate and silver ink. Sensor operating in K-band is developed providing a tradeoff between circuit size and droplet volume. The study is conducted for an artificial saliva requiring roughly a 0.5 µL droplet where changes in mixture content are proportional to relative changes of sensor`s transmission coefficient in a broad frequency range for occupied vs. empty states. The obtained results show that 10mg of glucose per 100ml of saliva can be easily distinguished in a frequency range of 20-30GHz, whereas a monotonical change is visible for frequencies 20-26GHz, which indicates the applicability of this sensor towards the detection of saliva-glucose levels and potential application in the detection of small amounts of other substances in liquids.

High-Resolution Total Internal Reflection-Based Structural Coloration by Electrohydrodynamic Jet Printing of Transparent Polyethylene Glycol Microdomes.

Total internal reflection (TIR)-based structural coloration is a brilliant strategy to overcome the need for periodic nanostructures and complex fabrication processes. Light entering the microdome structure undergoes TIR, and owing to varying reflection paths, it exhibits a color that changes with the microdome size. Although solution-based printing techniques have been proposed to achieve this effect, they fall short of full-color realization owing to resolution limitations. Herein, we achieved 3628 dpi of full-color and high-resolution structural color images by printing transparent microdome structures with 1.2-9.9 μm diameter using electrohydrodynamic (EHD) jet printing. Additionally, high-resolution EHD jet-printed structural color images display complex encoded information, enhancing the anticounterfeiting effectiveness through their fabrication simplicity and precise control over the microdome size. Because of these advantages, this TIR-based structural coloration technique with EHD jet printing is highly suitable for anticounterfeiting applications.

Conformally printed additively manufactured RF demonstrator for circuit compaction

Abstract Recently, there has been interest in applying Additive Manufacturing (AM) to RF and Microwave applications, especially in packaging of microelectronic devices. Additive packaging offers advantages of expanded functionality in restricted volume, through miniature, low-SWaP-C sensors, allowing for non-traditional form factors. In this work, design, fabrication, and characterization of a non-planar multi-material MMIC structure is presented to demonstrate significant footprint reduction and circuit compaction. Performance of a non-planar passive RF device and details of planar to non-planar AM connections for characterization of the transitions will be demonstrated. The work will present details of the design and fabrication of the non-planar structure, optimization of the process parameters for the Optomec 5-axis Aerosol Jet Printer for multi-material printing, and the results of the characterization and testing. RF measurements were conducted to demonstrate the functionality of the developed non-planar circuit and compared with simulations which showed good agreement. The results of this work show that fully additive approach is feasible for non-planar circuits, which will allow for footprint reduction, weight reduction, and achievement of novel form factors that are critical for microwave applications.

Advanced multi-nozzle electrohydrodynamic printing: mechanism, processing, and diverse applications at micro/nano-scale

Abstract Electrohydrodynamic (EHD) jet printing represents a novel micro/nano-scale additive manufacturing process that utilises a high-voltage induced electric field between the nozzle and the substrate to print micro/nanoscale structures. EHD printing is particularly advantageous for the fabrication on flexible or non-flat substrates and of large aspect ratio micro/nanostructures and composite multi-material structures. Despite this, EHD printing has yet to be fully industrialised due to its low throughput, which is primarily caused by the limitations of serial additive printing technology. The parallel multi-nozzle array-based process has become the most promising option for EHD printing to achieve large-scale printing by increasing the number of nozzles to realise multichannel parallel printing. This paper reviews the recent development of multi-nozzle EHD printing technology, analyses jet motion with multi-nozzle, explains the origins of the electric field crosstalk effect under multi-nozzle and discusses several widely used methods for overcoming it. This work also summarises the impact of different process parameters on multi-nozzle EHD printing and describes the current manufacturing process using multi-nozzle as well as the method by which they can be realised independently. In addition, it presents an additional significant utilisation of multi-nozzle printing aside from enhancing single-nozzle production efficiency, which is the production of composite phase change materials through multi-nozzle. Finally, the future direction of multi-nozzle EHD printing development is discussed and envisioned.

A Simple Pump-Free Approach to Generating High-Throughput Microdroplets Using Oscillating Microcone Arrays

Droplet generation is crucial in various scientific and industrial fields, such as drug delivery, diagnostics, and inkjet printing. While microfluidic platforms enable precise droplet formation, traditional methods often require costly and complex setups, limiting their accessibility. This study introduces a simple, low-cost approach using an off-the-shelf unit and a 3D-printed reservoir. The device, equipped with a driver board, piezo-ring transducer, and a metal sheet with holes, generates oil-in-water (O/W) droplets with an average diameter of 4.62 ± 0.67 µm without external fluid pumps. Its simplicity, cost-effectiveness, and scalability make it highly suitable for both lab-on-chip and industrial applications, demonstrating the feasibility of large-scale uniform droplet production.

Inkjet printing of mixed layers comprising multinary semiconductor quantum dots and charge transport materials for light‐emitting diode displays

AbstractQuantum dots (QDs) are important luminescent structures with applications in wide‐color‐gamut displays requiring exceptional color reproducibility. Multinary semiconductor QDs are expected to serve as eco‐friendly materials to replace conventional QDs owing to the narrow spectral widths and tunable bandgaps of these QDs. However, the application of multinary QDs, which tend to exhibit defect‐related emissions, to QD light‐emitting diode (QLED) displays will require electroluminescence to be obtained from QLEDs incorporating inkjet‐printed emitting layers. The present work examines QLEDs exhibiting vibrant color emissions based on blue‐emitting Zn–Se–Te QDs, green‐emitting Ag–In–Ga–S QDs, and red‐emitting Ag–Cu–In–Ga–S QDs. Each such QLED contains QD emitting layers comprising a mixture of charge transport materials. The spectra obtained from these RGB QLEDs fabricated by spin‐coating show very high color purity. Passive matrix QLED displays incorporating these QDs are also fabricated by inkjet printing to demonstrate the high color purity that can be obtained from multinary QDs in displays. In conjunction with passive matrix driving, these displays produce clear moving images with vibrant electroluminescence originating from the multinary QDs. The present results indicate that these QDs have significant potential for utilization in wide‐color‐gamut displays.

Thermophoretic particle deposition effect on a squeezed flow of radiative Jeffrey fluid past a sensor surface with uniform heat source/sink and chemical reaction

Abstract This anticipated model investigates the time-dependent, and incompressible 2D magnetized Jeffrey liquid flowing on a sensor surface placed between two infinite parallel plates with the existence of a uniform heat source/sink. The lower plate remains fixed while the upper plate is subject to squeezing. For the heat and mass transmission processes, the consequences of radiative heat flux, chemical reaction, and thermophoretic particle deposition are applied and analyzed. The envisioned model is supported by prescribed heat and mass flux conditions. The uniqueness of the proposed model is the analysis of the unsteady squeezed flow of Jeffrey liquid over a sensor surface, accounting for radiative heat flux, thermophoretic particle deposition, and variable thermal conductivity. The model possesses applications in microfluidic sensors, biomedical devices, thermal management systems, and inkjet printing. The equations comprising the model are subject to similarity transformations. The bvp4c package is utilized to analyze the dynamic flow system. The connotation of arising parameters with the associated profiles is depicted through graphs and tables. It is examined that fluid velocity, temperature, and concentration profiles are dwindling functions of squeezed parameter. It is also witnessed that the concentration of liquid drops with an enhancement of thermophoretic and chemical reaction parameters. The validation of the truthfulness of the envisioned model is an added feature of this study.

Scalable Fabrication of Neuromorphic Devices Using Inkjet Printing for the Deposition of Organic Mixed Ionic‐Electronic Conductor

AbstractRecent advancements in artificial intelligence (AI) have highlighted the critical need for energy‐efficient hardware solutions, especially in edge‐computing applications. However, traditional AI approaches are plagued by significant power consumption. In response, researchers have turned to biomimetic strategies, drawing inspiration from the ion‐mediated operating principle of biological synapses, to develop organic neuromorphic devices as promising alternatives. Organic mixed ionic‐electronic conductor (OMIEC) materials have emerged as particularly noteworthy in this field, due to their potential for enhancing neuromorphic computing capabilities. Together with device performance, it is crucial to select devices that allow fabrication via scalable techniques. This study investigates the fabrication of OMIEC‐based neuromorphic devices using inkjet printing, providing a scalable and material‐efficient approach. Employing a commercially available polymer mixed ionic‐electronic conductor (BTEM‐PPV) and a lithium salt, inkjet‐printed devices exhibit performance comparable to those fabricated via traditional spin‐coating methods. These two‐terminal neuromorphic devices demonstrate functionality analogous to literature‐known devices and demonstrate promising frequency‐dependent short‐term plasticity. Furthermore, comparative studies with previous light‐emitting electrochemical cells (LECs) and neuromorphic OMIEC devices validate the efficacy of inkjet printing as a potential fabrication technique. The findings suggest that inkjet printing is suitable for large‐scale production, offering reproducible and stable fabrication processes. By adopting the OMIEC material system, inkjet printing holds the potential for further enhancing device performance and functionality. Overall, this study underscores the viability of inkjet printing as a scalable fabrication method for OMIEC‐based neuromorphic devices, paving the way for advancements in AI hardware.

Manufacturing the current flow diverter architecture in REBCO tapes using silver inkjet printing

Abstract A low normal zone propagation velocity (NZPV) combined with critical current inhomogeneities favor the nucleation of destructive hot spots in rare-earth barium copper oxide (REBCO) tapes. Increasing the NZPV using the current flow diverter (CFD) concept is a promising solution to mitigate the risk of developing hot spots. The fabrication method of CFD REBCO tapes implies several steps consisting in masking, silver etching, mask removal, and silver deposition, which takes time and remains a barrier to the implementation of a low-cost industrial production of long-length CFD REBCO tapes. This work presents a cost-effective and maskless CFD fabrication approach that relies on inkjet printing (IJP) of silver patterns directly on top of the REBCO layer to create a non-uniform interfacial resistance between the silver and the REBCO surface, along the width of the tape. The parameters of IJP and oxygen annealing were optimized to obtain highly conductive silver patterns deposited on the surface of the REBCO layer. CFD REBCO tapes were successfully fabricated using commercial REBCO tapes and the proposed method without degrading the superconducting properties. Experimental measurements revealed an increase of the NZPV by a factor of 6-7 compared to commercial REBCO tapes.

On the electrohydrodynamic jet printing of two-dimensional material-based inks for printed electronics

Electrohydrodynamic (EHD) jet printing is a well-known advanced manufacturing technique that uses electric fields to generate and control fine jets of fluid for high-precision deposition of materials. This method enables the printing of extremely fine features, making it ideal for applications such as printed electronics. However, little is known about the optimal conditions for achieving consistent jet stability and droplet formation, especially when dealing with complex and volatile fluids laden with two-dimensional (2D) nanoparticles. In this work, we study the electrohydrodynamic printing process of 2D material-based inks using toluene as the main carrier fluid. Adding ethyl cellulose to toluene allows us to increase the stability of the suspensions and establish the steady cone-jet mode of electrospray. A small amount of ethanol increases the fluid conductivity, stabilizing the steady cone-jet mode and reducing the jet diameter. The inks behave as leaky-dielectric, weakly viscoelastic liquids. For this reason, the jet diameter and minimum flow rate obey the scaling laws for electrospray of Newtonian liquids. We determine the optimal parameter conditions for the EHD printing of our inks directly onto a non-conductive substrate. The influence of the substrate's velocity on the width of the printed lines is analyzed. These findings enlarge the knowledge about how to increase the throughput in the EHD jet printing process while controlling the resolution of the printed lines when using volatile solvents, 2D nanomaterials, and non-conductive substrates.

3D printing of NMC-based patterned electrodes by inkjet printing

3D printing of NMC-based patterned electrodes by inkjet printing

Realizing Arbitrary 3D Microarchitectures with Curved and near-Sharp Segments via Toolpath Strategies in Aerosol Jet Printing

Aerosol Jet (AJ) printing is a jetting-based additive manufacturing (AM) technique that uses droplets in an aerosol form to deposit nanoparticles or polymer inks at a length scale of about 10 micrometers. The desired structural geometries via AJ printing can be obtained at a high efficiency and accuracy by engineered toolpaths and fill strategies. Recently, AJ printing is used to create three-dimensional (3D) freestanding microarchitectures such as microlattices, spirals, walls, and micropillars without any auxiliary support during printing. In this work, we demonstrate that for curved segments, the difference in the printed material volume on the convex side vs concave side leads to the accumulation of material while building freestanding 3D microarchitectures. This effect is most severe for sharp corners, which leads to build-defects such as protrusions and voids. We carry out a systematic study of the material accumulation on curved segments of AJ printed 3D microarchitectures. For 3D microwall segments with sharp curved portions, a positive (or negative) material accumulation causing large overgrowths (or voids) as a function of the angle between the tangents on the two sides of the microwalls and the radii of curvature are studied. For sharp bends (<15°) in the microwalls, adding a radius of curvature may not be sufficient to avoid overgrowths and voids, and the lines can be considered as individual segments. For microwall bends with >45°, smaller radii of curvature can be tolerated. We conclude that a fillet radius equal to the line width for 30° angles is necessary to avoid accumulation and therefore the protrusion defects. A simple model based on mass-conservation is also developed which shows the importance of considering ink self-leveling during printing. This information is then used for toolpath strategies to avoid defects on sharp curved microwall segments for complex 3D architectures such as protruding star shape and Scotty Dog, the Carnegie Mellon University mascot. This research will enable the defect-free fabrication of highly complex 3D microarchitectures via jetting-based AM techniques such as AJ printing.

Tailorable Fluorescent Perovskite Quantum Dots for Multiform Manufacturing via Two-Step Thiol-Ene Click Chemistry.

In practical applications, fluorescent perovskite quantum dots (PQDs) must exhibit high efficiency, stability, and processibility. So far, it remains a challenge to synthesize PQDs with stable dispersibility in tailorable monomers both before and after photocuring. In this work, a novel strategy of UV-induced two-step thiol-ene "click chemistry" is proposed to prepare PQDs with these attributes. The first step aims to epitaxially grow a shell around the PQD core to ensure stable dispersibility in a thiol-ene monomer solution. The second step is to achieve stable dispersibility in the photocured thiol-ene matrixes for multiform manufacturing processes. The tailorable PQDs (T-PQDs) not only have the highest photoluminescence quantum yield (PLQY) to ≈100% for green emission and over 96% for red emission, but also exhibit remarkable stability under severe conditions, including "double 85" aging, water exposure, and mechanical stress. Moreover, their exceptional processability allows for various processing techniques, including slot-die coating, inkjet printing, direct-laser writing, UV-light 3D printing, nanoimprinting, and spin coating. The high efficiency and stability of T-PQDs facilitate their multiform manufacturing for a wide range of applications.

Numerical Analysis of the Cell Droplet Loading Process in Cell Printing

Cell printing is a promising technology in tissue engineering, with which the complex three-dimensional tissue constructs can be formed by sequentially printing the cells layer by layer. Though some cell printing experiments with commercial inkjet printers show the possibility of this idea, there are some problems, such as cell damage due the mechanical impact during cell direct writing, which include two processes of cell ejection and cell landing. Cell damage observed during the bioprinting process is often simply attributed to interactions between cells and substrate. However, in reality, cell damage can also arise from complex mechanical effects caused by collisions between cell droplets during continuous printing processes. The objective of this research is to numerically simulate the collision effects between continuously printed cell droplets within the bioprinting process, with a particular focus on analyzing the consequent cell droplet deformation and stress distribution. The influence of gravity force was ignored, cell droplet landing was divided into four phases, the first phase is cell droplet free falling at a certain velocity; the second phase is the collision between the descending cell droplet and the pre-existing cell droplets that have been previously printed onto the substrate. This collision results in significant deformation of the cell membranes of both cell droplets in contact; the third phase is the cell droplet hitting a rigid body substrate; the fourth phase is the cell droplet being bounced. We conducted a qualitative analysis of the stress and strain of cell droplets during the cell printing process to evaluate the influence of different parameters on the printing effect. The results indicate that an increase in jet velocity leads to an increase in stress on cell droplets, thereby increasing the probability of cell damage. Adding cell droplet layers on the substrate can effectively reduce the impact force caused by collisions. Smaller droplets are more susceptible to rupture at higher velocities. These findings provide a scientific basis for optimizing cell printing parameters.

Inkjet printing of polyurethane micro/nanofibers using TiO2 and Ag NPs on as‐spun mats for enhancing tissue engineering applications

Inkjet printing of polyurethane micro/nanofibers using <scp>TiO₂</scp> and Ag <scp>NPs</scp> on as‐spun mats for enhancing tissue engineering applications

Rapid Prototyping of Multiscale Flexible Printed Circuit Boards with NeXus, a Robotic Additive Manufacturing System

Abstract This paper demonstrates the NeXus system, a multi-scale robotic additive manufacturing platform developed at the Louisville Automation and Robotics Research Institute (LARRI), as a rapid prototyping tool through additively manufacturing a multi-layer flexible printed circuit board (FPC) with a printed strain sensor and soldered Surface Mounted Devices (SMD). Manufacturing of the demonstrator requires the application and curing of multiple materials with specialized properties, tools for automated assembly, and software advances to streamline the process enabling the use of industry-standardized programs to command the NeXus system. Additive manufacturing processes supported by the NeXus include Aerosol Jet printing (AJP) for fine feature silver conducting lines, direct write ink-jet printing for insulating materials, and Intense Pulsed Light (IPL) for curing materials between depositions. The NeXus system transports and manipulates parts using a 5-DOF high-precision positioner. Solder paste deposition and pick-and-place (PnP) procedures are performed by a 4-DOF Selective Compliance Articulated Robot Arm (SCARA). Conversion methods between traditional PCB design software and production-ready command scripts were developed to translate basic drawings into command scripts. Multilayer structures with AJP 50-micron wide lines, an insulating bridge with a thickness of around 100 microns, and SMDs soldered to silver AJP pads, were integrated within the demonstrator. An operational amplifier, and other SMDs, reduce the complexity of the accompanying control circuit and amplifies the sensor?s response by 1,830 times. The successful fabrication of the demonstrator FPC highlights the rapid prototyping ability of the NeXus System.

Hydrophobically Modified Polyacrylamide Incorporating Both Hydrophilic and Hydrophobic Units: Enhanced Printability and Stability in Aqueous Ink.

For this research, three hydrophobically modified polyacrylamides, HPAAB, HPAAF, and HPAAS, with multiple hydrophobic monomers were designed, synthesized, and used as thickeners in aqueous ink for digital ink-jet printing. The structures were characterized by Fourier transform infrared (FTIR) analysis and nuclear magnetic resonance (NMR) spectroscopy. The viscosity-average molecular weight was determined by intrinsic viscosity determination and was adjusted according to hydrophobic content. The critical association concentration (CAC) of polymers was measured simultaneously using the apparent viscosity method and the fluorescence spectrum. The formation of a network structure and the mechanism of hydrophobic association are visualized dynamically with a scanning electron microscope (SEM) at different concentrations. Under the same conditions, HPAAB exhibited excellent thickening ability across different pH levels, temperatures, and shear rates, which is caused by the longer hydrophobic side chain and the stronger hydrophobic effect of the behenyl polyoxyethylene ether methacrylate (BEM) group. Furthermore, an aqueous ink using HPAAB as a thickener displays significant printability and stability, functioning much better than a corresponding aqueous ink that uses a commercial thickener. This is the first example of a hydrophobic associating polyacrylamide, incorporating both hydrophilic and hydrophobic units within a single hydrophobic chain, thereby serving as an efficient thickener for aqueous ink.

Emerging Technological Advancement for Chronic Wound Treatment and Their Role in Accelerating Wound Healing.

Chronic wounds are a major healthcare burden and may severely affect the social, mental, and economic status of the patients. Any impairment in wound healing stages due to underlying factors leads to a prolonged healing time and subsequently to chronic wounds. Traditional approaches for the treatment of chronic wounds include dressing free local therapy, dressing therapy, and tissue engineering based scaffold therapies. However, traditional therapies need improvisation and have been advanced through breakthrough technologies. The present review spans traditional therapies and further gives an extensive account of advancements in the treatment of chronic wounds. Cutting edge technologies, such as 3D printing, which includes inkjet printing, fused deposition modeling, digital light processing, extrusion-based printing, microneedle array-based therapies, gene therapy, which includes microRNAs (miRNAs) therapy, and smart wound dressings for real time monitoring of wound conditions through assessment of pH, temperature, oxygen, moisture, metabolites, and their use for planning of better treatment strategies have been discussed in detail. The review further gives the future direction of treatments that will aid in lowering the healthcare burden caused due to chronic wounds.

Wetting phenomena of droplets and gas bubbles: Contact angle hysteresis based on varying liquid-solid and solid-gas interfacial tensions.

Wetting phenomena have been widely observed in our daily lives, such as dew on lotus leaf, and applied in technical applications, e.g., ink-jet printing. In contrast to constant liquid-solid and solid-gas interfacial tensions in Young's law, we here focus on the wetting phenomena by considering varying fluid-solid interfacial tensions. We analyze the energy landscape, the map of Young's contact angle, the number and corresponding contact angle of local energy minima, and the contact angle hysteresis for a liquid droplet on a solid substrate in a gas phase. In addition, a gas bubble on a solid substrate in a liquid phase has been scrutinized from the aspect of surface energy minimization. The wetting effect has been regarded, where the liquid and gas species penetrate into the solid phase on the microscopic scale [F. Wang and B. Nestler, Phys. Rev. Lett. 132, 126202 (2024)]. We assume the liquid-solid and the solid-gas interfacial tensions to be a function dependent on the volume fraction of the liquid and the gas species and investigate the impact of the size ratio of the droplet to the solid surface that is overlooked in existing theories on the wetting phenomena. Our finding sheds light on the microscopic origin of the contact angle hysteresis and the droplet size effect on the wetting phenomena.