Electrohydrodynamic Jet Research Articles

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.

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.

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.

Functional Ligand‐Modified Perovskite Quantum Dots for Stable Full‐Color Microarrays via Photopolymerization

AbstractIntegration of lead‐halide perovskite quantum dots (PQDs) into full‐color microarrays presents numerous advantages for full‐color micro‐LED displays. There is an urgent requirement for a new design approach that simplifies the creation of durable PQD/polymer composites to produce stable PQD microarrays. Here, mono‐2‐(methacryloyloxy)ethyl succinate (MMeS) is utilized as a functional ligand to synthesize green MMeS‐modified CsPbBr3 PQDs (M‐CPB PQDs). The subsequent photopolymerization of M‐CPB PQDs with 1,6‐hexanediol diacrylate (HDDA) forms a CsPbBr3 PQD/polymer composite. This composite exhibits a solid‐state photoluminescence quantum yield of 73.1%, and the photoluminescence intensity retains 72% of its original value after 17 days of continuous immersion in water. Stable green PQD/polymer microarrays can be printed using an ink containing M‐CPB PQDs, HDDA, diphenyl (2,4,6‐trimethylbenzoyl) phosphine oxide, and n‐dodecane via electrohydrodynamic jet printing and in situ polymerization under UV light irradiation. Full‐color patterns can also be generated with MMeS‐modified red, green, and blue PQDs. These findings highlight the critical role of functionalizing the surface ligands of PQDs to improve their processability, thereby facilitating the development of stable PQD/polymer microarrays.

Laser-induced in-situ electrohydrodynamic jet printing of micro/nanoscale hierarchical structure

With the rapid advancement of micro/nanoscale devices, there is a growing demand for hierarchical micro/nano porous-structure, particularly in fields of high-performance sensors, electrochemical energy storage, and photocatalysis. The fabrication methods for hierarchical micro/nano-porous structures have been limited by complex processes and high costs, making further development and application difficult. In this paper, a novel strategy of laser-induced in-situ electrohydrodynamic jet (E-Jet) printing of hierarchical micro/nano-porous structures was proposed. Based on the mechanism of high-energy laser beam induction on the jet, it successfully fabricated hierarchical porous ZnO structures from nanoscale to dozens of microns. The jet size focusing and solidification behavior were analyzed by combining experimental and simulative exploration. The resultant effects of the thermal field, flow field, and laser field on the spatial temperature distribution and the jetting morphology were examined. Furthermore, the laser-induced influence on the morphology of the printed micro/nano-porous ZnO structures was explored. Meanwhile, the performance of micro/nano-porous ZnO photoelectric sensors printed by E-Jet under different laser powers was investigated. The laser-induced in-situ E-Jet printing method provided an innovative pattern for the high-resolution additive manufacturing of hierarchical porous structures, demonstrating its potential for applications in advanced material and high-performance devices.

Fabrication and Characterization of PZT Thick Film Microstructure and T-Shaped Generator by Electrohydrodynamic Jet Printing

Fabrication and Characterization of PZT Thick Film Microstructure and T-Shaped Generator by Electrohydrodynamic Jet Printing

Fabrication and Characterization of Zinc Oxide Nanorods on Electrohydrodynamic Jet Printed Silver Micropillars

Fabrication and Characterization of Zinc Oxide Nanorods on Electrohydrodynamic Jet Printed Silver Micropillars

Droplet volume prediction methods in electrohydrodynamic jet printing based on multi-source data fusion

Electrohydrodynamic jet printing technology has garnered significant interest in additive manufacturing due to its advantages in higher resolution printing and greater viscosity material applicability. Nonetheless, the challenges associated with femtoliter-level droplets and the micrometer-scale printing space have rendered traditional optical observation methods for volume calculation impractical for integration into the printing systems. Obtaining the droplet volume accurately has become a formidable challenge in electrohydrodynamic printing. While existing research utilizes machine learning for the end-to-end prediction of process parameters to droplet volume, traditional prediction methods cannot achieve online prediction due to the complex spray states characteristic of electrohydrodynamic jet printing and pose integration difficulties within printing systems. This paper introduces a multi-source data fusion model suitable for electrohydrodynamic printing droplet volume prediction. The model employs the VGG network to extract features from Taylor cone images in the jetting state and synchronously fuse these with process parameter features. The fused features are then correlated with droplet volume labels through the MLP network for comprehensive model training. The performance of the proposed model has improved by 10% in prediction accuracy compared to single modal data. We integrated the prediction method into an electrohydrodynamic jet printing system and experimented with printing pixel-pit substrates. The results indicate that the prediction accuracy of the volume prediction system is over 92%. The printing efficiency has improved approximately 3 times compared to the traditional method, significantly enhancing overall performance.

3D printing cross‐scale mold for manufacturing micromixers

AbstractNowadays, the methods of manufacturing microfluidic mixers were not flexible enough to customize and manufacture special sizes. Hence, a novel electrohydrodynamic jet printing method was proposed to fabricate cross‐scale mold for manufacturing micromixers in one step. Polyvinylpyrrolidone (PVP)/polycaprolactone (PCL) composite ink was prepared, and various printing parameters were investigated for fabricating varieties of 2D structures and 3D regular molds. A cross‐scale spiral mixer was successfully printed, various diameter ratio of 5.6, aspect ratio of 7.2. The PVP/PCL lines were direct printed, size of 66 nm deep and 743 nm wide. The circles were size of 564 nm deep and 7.02 μm wide. The mixing conditions of micromixers with different width ratios were simulated and analyzed; and the better mixing effect of micromixers with width ratio of 2:1 was proved, improved the mixing efficiency by 15.6% compared with micromixer without cross‐scale channels. The cross‐scale micromixers are promising for skin chip sensor and drug metabolite analysis, and the printing method proposed in this paper has great application potential in micro‐electro‐mechanical systems (MEMS).

Synthetic Protein Nanoparticles via Photoreactive Electrohydrodynamic Jetting.

Protein nanoparticles are an attractive class of materials for nanomedicine applications due to the intrinsic biocompatibility, biodegradability, and intrinsic functionality of their constituent proteins. Despite the clinical success of select protein nanoparticles, this class of nanocarriers remains understudied and underdeveloped compared to lipid and polymer nanoparticles due to challenges related to formulation optimization, large design space, and their structural complexity. In this work, a modular strategy for protein nanoparticle preparation based on the concept of photoreactive jetting is introduced. The process relies on continuous ultravioletirradiation during electrohydrodynamic (EHD) jetting of protein solutions that contain a homobifunctional photocrosslinker. Protein nanoparticles exhibit nanogel-like architectures comprised of proteins that are linked via synthetic moieties. Compared to conventional protein nanoparticles, this method reduces nanoparticle processing times to minutes, rather than hours to days. The inclusion of an emissive structural motif as the molecular scaffold of the photocrosslinker is used to study the supramolecular architecture of the stable nanoparticles via time-resolved fluorescence spectroscopy.

Fabrication of a microfluidic system with in situ-integrated microlens arrays using electrohydrodynamic jet printing

Microfluidic systems with integrated microlenses enhance cellular analysis and observation and have gained significant attention in the biomedical field. However, the integration and design of microlenses in microfluidic systems remain challenging. In this study, we utilize a high-precision electrohydrodynamic jet (E-jet) printing system for in-situ integration of microlens. By incorporating a tilting illumination observation module into the E-jet printing system, the print nozzle can be accurately positioned 10 μm above the microchannel bottom, thereby mitigating the edge effect of the microfluidic channels. We have developed a microfluidic system embedding microlens arrays (MLAs) that enable parallel, multichannel cell counting. The microfluidic system comprises nine channels, each featuring a 50 μm diameter microlens printed along the central axis. Using microlenses enables non-contact cell counting by detecting light-intensity changes. Simulating and optimizing the microfluidic channel size enable cells to align on the centerline of the channel and pass over the focal region of the microlens via inertial forces. As the cells flow through the microlens, the intensity of the focal spots decreases by approximately 50 %. The microfluidic cell-counting system can function independently or be integrated with other microfluidic systems as a unit, thus enhancing the single-cell operational and analytical capabilities of microfluidic systems.

Investigation of process parameters of electrohydrodynamic jetting for 3D printed PCL fibrous scaffolds with complex geometries

Tissue engineering is a promising technology in the field of regenerative medicine with its potential to create tissues de novo. Though there has been a good progress in this field so far, there still exists the challenge of providing a 3D micro-architecture to the artificial tissue construct, to mimic the native cell or tissue environment. Both 3D printing and 3D bioprinting are looked upon as an excellent solution due to their capabilities of mimicking the native tissue architecture layer-by-layer with high precision and appreciable resolution. Electrohydrodynamic jetting (E-jetting) is one type of 3D printing, in which, a high electric voltage is applied between the extruding nozzle and the substrate in order to print highly controlled fibres. In this study, an E-jetting system was developed in-house for the purpose of 3D printing of fibrous scaffolds. The effect of various E-jetting parameters, namely the supply voltage, solution concentration, nozzle-to-substrate distance, stage (printing) speed and solution dispensing feed rate on the diameter of printed fibres were studied at the first stage. Optimized parameters were then used to print Polycaprolactone (PCL) scaffolds of highly complex geometries, i.e., semi-lunar and spiral geometries, with the aim of demonstrating the flexibility and capability of the system to fabricate complex geometry scaffolds and biomimic the complex 3D micro-architecture of native tissue environment. The spiral geometry is expected to result in better cell migration during cell culture and tissue maturation.

Properties of WS2-based multiple-layer films deposited by electrohydrodynamic jet deposition

This paper aims to provide efficient methods for enhancing the mechanical properties and tribological performance of WS2-based film. Pure WS2 film (SW), WS2-Ni composite film (SWN), WS2/WS2-Ni/Ni multiple-layer film (SWN-g), and WS2/WS2-Ni/Ni multiple-layer film on textured surface (SWN-t) were prepared on the cemented carbides substrates by electrohydrodynamic jet deposition. The surface morphology and composition of the deposited films were observed through scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) elemental analysis. The mechanical properties of films were measured through nanoindentation experiments, while the adhesion strength between the film and substrate was evaluated through scratch tests. The friction and wear performance were investigated through reciprocating sliding friction tests. Results indicated that multiple-layer film deposited on the textured surface (SWN-t) exhibited great tribological properties, it has the lowest friction coefficient and the highest adhesion strength. Compared with the pure WS2 film, the average friction coefficient decreased by 66.1 %, and the adhesion strength between films and substrate increased by 50.4 %.

Silver Nano-Inks Synthesized with Biobased Polymers for High-Resolution Electrohydrodynamic Printing Toward In-Space Manufacturing.

Electrohydrodynamic (EHD) printing is an additive manufacturing technique capable of producing micro/nanoscale features by precisely jetting ink under an electric field. However, as a new technique compared to more conventional methods, commercially available inks designed and optimized for EHD are currently very limited. To address this challenge, a new silver nanoink platform was developed by synthesizing silver nanoparticles in situ with biobased polymer 2-hydroxyethyl cellulose (HEC). Typically used as a thickening agent, HEC is cost-effect, biocompatible, and versatile in developing inks that meet the rheology criteria for high-resolution EHD jetting. This approach significantly outperforms the traditional use of polyvinylpyrrolidone (PVP), enabling the stabilization of high solids content (>50 wt %) nanoinks for over 10 months with an HEC dosage 20 times lower than that required by PVP. The HEC-synthesized silver ink displays excellent electrical properties, yielding resistivities as low as 2.81 μΩ cm upon sintering, less than twice that of pure silver. Additionally, the capability to sinter at low temperatures (<200 °C) enables the use of this ink on polymer substrates for flexible devices. The synthesized nanoinks were also found to be capable of producing precise, high-resolution features by EHD printing with smooth lines narrower than 5 μm printed using a 100 μm nozzle. Additionally, a semiempirical model was developed to reveal the relationship between printing resolution, ink properties, and printing parameters, enabling precise printing control. Moreover, for the first time, the unique ability of EHD to achieve precise fabrication under microgravity was conclusively demonstrated through a parabolic flight test utilizing the HEC-based nanoinks. The study greatly expands the potential of printing thin films for the on-demand manufacturing of electronic devices in space.

All-printed 3-dimensional micro-supercapacitors with homogeneous Ag interface: Achieving precision on curved surfaces through Electrohydrodynamic jet printing

Despite advancements in manufacturing techniques for micro-supercapacitors (MSCs), significant challenges remain in achieving on-chip miniature devices that conform to complex surfaces, which is crucial for the seamless integration in advanced electronic systems. This study utilizes direct electrohydrodynamic (EHD) 3-dimensional (3D) printing to fabricate all-printed MSCs on planar and curved surfaces, employing Ag as a base material for both current collectors and electrodes to ensure homogeneous interfaces throughout the printed structures. Our approach uniquely manipulates the applied nozzle voltage in the EHD 3D printing process to achieve finely controlled and uniform 3D structures on both flat and curved surfaces. The high-precision EHD jet printer produces MSCs with notably narrow electrode linewidths of approximately 144μm. A 3D MSC cell is then fabricated with 15 EHD 3D-printed stacked layers to achieve a remarkable electrode-line height/width (h/w) ratio of 4.2, which exhibits exceptional electrical performance with an areal capacitance of 763.1 mF cm−2 and energy density of 256.6 μWh cm−2. Additionally, multiple MSCs are EHD 3D-printed on a curved substrate to successfully energize an LED. These findings verify that EHD 3D printing can be utilized to fabricate scalable energy storage devices that can be easily integrated with the next generation electronic systems.

Patterned microsphere-lens projection lithography using an electrohydrodynamic-jet-printing-assisted assembly

Microlens arrays have been widely used in the fields of micro-optics and micro- and nanofabrication. Traditional preparation methods utilize commercial photoresists and thermosetting materials, thereby restricting the optical properties of microlenses. In recent years, significant advancements have been achieved in near-field super-resolution imaging by utilizing microspheres and forming arrays of microsphere lenses via self-assembly. However, self-assembly approaches lack flexibility in terms of pattern selection. This study proposes a method that utilizes electrohydrodynamic jet (E-jet) printing to code ultraviolet (UV)-curable adhesives and assist in the assembly of patterned microsphere-lens arrays. Simulation results demonstrate that the UV-curable adhesive has little impact on the optical properties of the microsphere lens. Moreover, the microsphere lens exhibits a superior imaging resolution compared with traditional microlenses. A projection-lithography system is developed to achieve an accurate alignment between the focal plane of the microsphere lenses and the plane of the photoresist, facilitating the fabrication of patterned nanostructures. The lithographic nanostructures have a minimum feature size of 850 nm. This method enables the fabrication of arrays of microsphere lenses with arbitrary patterns and presents an inexpensive and simple strategy for fabricating micro- and nanostructure arrays with submicrometer features.

Controlled Delivery of Paclitaxel via Stable Synthetic Protein Nanoparticles

AbstractDespite decades of intense research, glioma remains a disease for which no adequate clinical treatment exists. Given the ongoing therapeutic failures of conventional treatment approaches, nanomedicine may offer alternative options because it can increase the bioavailability of drugs and alter their pharmacokinetics. Here, a new type of synthetic protein nanoparticles (SPNPs) is reported that allow for effective loading and controlled release of the potent cancer drug, paclitaxel (PTX) – a drug that so far has been unsuccessful in glioma treatment due to hydrophobicity, low solubility, and associated delivery challenges. SPNPs are prepared by electrohydrodynamic (EHD) jetting of dilute solutions of PTX‐loaded albumin made by high‐pressure homogenization. After EHD jetting, PTX SPNPs possess a dry diameter of 165 ± 44 nm, hydrated diameter of 297 ± 102 nm, and a zeta potential of −19 ± 8 mV in water. For the SPNP formulation with a total PTX loading of 9.4%, the loading efficiency is 94%, and controlled release of PTX is observed over two weeks (6% burst release). PTX SPNPs are more potent (68% lethality) than free PTX (45% lethality using 0.2% dimethyl sulfoxide). PTX SPNPs in combination with IR show a significant survival benefit in glioma‐bearing mouse models, avoid adverse liver toxicity, and maintain a normal brain architecture. Immunohistochemistry reveals a dramatic tumor size reduction including 40% long‐term survivors without discernible signs of tumor. Using flexibly engineered SPNPs, this work outlines an efficient strategy for the delivery of hydrophobic drugs that are otherwise notoriously hard to deliver.

Ultrasensitive composite electrochemical sensor with printed wrinkled CNTs nanostructure for simultaneous detection

Combining biomimetic and 3D printing has created new opportunities for the manufacture of electrochemical sensors. Dopamine (DA) and Uric acid (UA) are common body electroactive substances, and their detection is important for diagnosing metabolic diseases. Metal electrochemical sensors have limitations in sensitivity and selectivity due to their smooth 2D structures, which make it challenging to capture comprehensive electrochemical information. Here, inspired by taste buds, an ultrasensitive CNT-Pt composite electrochemical sensor, including a printed biomimetic wrinkled CNTs film, was prepared for simultaneous detection of DA and UA. Nanoscale Pt electrode was prepared by UV-LIGA process and the wrinkled CNTs nanofilm was fabricated by thermally assisted electrohydrodynamic jet (E-Jet) printing. CNT lines of 3∼58 μm, droplets of 4 μm and 2D array structures have been printed. The enhanced sensing mechanism of wrinkled CNTs nanofilm was analyzed theoretically. The nanoscale wrinkled morphology (nanofolds∼50 nm) and hydrophilicity (CÃ20°) of printed wrinkled CNTs nanofilm were analyzed. The anodic peak potential for UA was observed to range from 0.429 V to 0.489 V for the conventional Pt electrochemical sensor, whereas it ranged from 0.205 V to 0.276 V for the CNT-Pt composite electrochemical sensor. The detection performance of CNT-Pt composite electrochemical sensor was improved by ∼40 % contrast with Pt electrochemical sensor. The prepared composite electrochemical sensor can effectively recognize DA, UA and AA. From analysis, the peak value of AA was not obvious, the peak values of DA and UA were 0.096 V and 0.265 V. The composite electrochemical sensor successfully eliminated the detection interference caused by AA in detecting DA and UA. The nanoscale composite electrochemical sensor and its hybrid manufacturing method provide great potential for electrochemical testing applications.

Laser-assisted electrohydrodynamic jet printing of hierarchical nanostructure

The hierarchical nanostructures had the advantages of large available space, specific surface area, low density, variable chemical composition, and controllable porosity, and have been widely used in energy, sensor, and catalysis. Traditional methods for preparing hierarchical nanostructures had limitations of a long process, few available materials, and un-customizable size. Electrohydrodynamic jet (E-Jet) printing is a competitive strategy for high-resolution printing. In this paper, a novel laser-assisted E-Jet printing employed a transient high-energy laser effect instead of a traditional continuously thermal effect for printing hierarchical nanostructure. The colorless ZnO ink was prepared with zinc acetate, diethanolamine, PVP, and ethanol. The transient thermal effect of laser irradiation focused a fine jet and induced Taylor cone expansion. The heat accelerated the solvent evaporation and increased the viscous force of the jet. The effects of laser on jet velocity, electric field, and jet behavior were analyzed theoretically. Characterization and 3D morphology of printed nanostructures with and without laser were investigated. The hierarchical nanostructures with size down to 180 nm could be laser-assisted E-Jet printed and its surface area increased multiply. The laser-assisted E-Jet printing method provides a simple, efficient, and low-cost strategy for preparing hierarchical nanostructure, having potential applications in high-performance devices.

Direct writing of suspended nanowires using coaxial electrohydrodynamic jet with double tip assistance

Direct writing of suspended nanowires using coaxial electrohydrodynamic jet with double tip assistance