Search

Exploring new horizons in phototransistors with an emphasis on mass customization is essential. Herein, a method for enhancing the performance of indium‐gallium‐zinc‐oxide (IGZO) phototransistors by incorporating a selectively formed tungsten trioxide (WO3) photocatalytic layer, utilizing electrohydrodynamic (EHD) jet‐printing is proposed. This approach aims to achieve significant manufacturing advantages and enhance functionality. An oxidizing solution of hydrogen peroxide (H2O2) doped with hydroxyethyl cellulose (HEC) is introduced to selectively oxidize tungsten (W) electrodes. In this mixture, H2O2 is responsible for the selective oxidation of W, whereas HEC contributes to the viscosity regulation and the formation of subgap states. The resulting selectively oxidized photocatalytic layer significantly expands its visible light absorption capacity to red light. Therefore, the optimized device, particularly under red light (635 nm) 5 mW mm−2, shows a remarkable enhancement in its optoelectronic characteristic: photoresponsivity increases from 29.71 to 124.54 A W−1, photosensitivity from 1.99 × 10‐1 to 1.79 × 104, and detectivity from 1.31 × 107 to 1.98 × 108 Jones compared to IGZO phototransistors without selectively oxidized photocatalytic layer. This advancement not only enhances the visible light detection capacity but also minimizes the persistent photoconductance issue inherent in IGZO devices. The demonstration of 6 × 6 phototransistor array illustrates the potential for image sensor applications, showcasing the practicality of mass customization. [ABSTRACT FROM AUTHOR]

Copyright of Micronanoelectronic Technology is the property of Micronanoelectronic Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Electrohydrodynamic jet (E‐Jet) printing is a highly promising non‐contact additive manufacturing technology. However, the fast jets generated by E‐Jet may cause droplet accumulation on small curvature features due to the slow motion control achieved by the mechanical stage, leading to a degradation of printed patterns in localized areas. Here, a method is proposed for ultrafast modulation of jet trajectories to achieve finely patterned E‐Jet printing by introducing jet‐deflecting electrodes around the jet, which can continuously transform the jet trajectory with lateral acceleration up to 104 ms−2. This extraordinary acceleration is two orders of magnitude higher than that can be achieved by using mechanical stage motion. Through a combination of numerical calculations and experiments, the effects of electric field parameters on the feature size and kinematic properties of jet droplets are investigated. In addition, deposition errors of <5 µm are fabricated by selecting appropriate working parameters and using UV‐curable adhesives as printing ink. Subsequently, complex micropatterns with feature curvatures <4 µm are successfully printed, demonstrating the consistency and reliability of this electrostatic deflection technique in achieving a uniform droplet deposition pitch. This innovative approach holds significant promise in the field of high‐quality microscale additive manufacturing. [ABSTRACT FROM AUTHOR]

Electrohydrodynamic (EHD) jet printing of solvent-based inks or melts allows for the producing of polymeric fiber-based two- and three-dimensional structures with sub-micrometer features, with or without conductive nanoparticles or functional materials. While solvent-based inks possess great material versatility, the stability of the EHD jetting process using such inks remains a major challenge that must be overcome before this technology can be deployed beyond research laboratories. Herein, we study the parameters that affect the stability of the EHD jet printing of polyethylene oxide (PEO) patterns using solvent-based inks. To gain insights into the evolution of the printing process, we simultaneously monitor the drop size, the jet ejection point, and the jet speed, determined by superimposing a periodic electrostatic deflection. We observe printing instabilities to be associated with changes in drop size and composition and in the jet's ejection point and speed, which are related to the evaporation of the solvent and the resulting drying of the drop surface. Thus, stabilizing the printing process and, particularly, the drop size and its surface composition require minimizing or controlling the solvent evaporation rate from the drop surface by using appropriate solvents and by controlling the printing ambient. For stable printing and improved jet stability, it is essential to use polymers with a high molecular weight and select solvents that slow down the surface drying of the droplets. Additionally, adjusting the needle voltages is crucial to prevent instabilities in the jet ejection mode. Although this study primarily utilized PEO, the general trends observed are applicable to other polymers that exhibit similar interactions between solvent and polymer. [ABSTRACT FROM AUTHOR]

To improve the resolution of printed patterns fabricated with PEDOT:PSS organic conductive polymer printing solutions by an electrohydrodynamic (EHD) jet printing method, the EHD jet printing method based on the high-voltage electrostatic focusing lens was proposed based on the analysis of the theoretical model of the EHD jet printing method. Using the PEDOT:PSS mixed solution as the printing solution, flexible conductive patterns were printed on the photographic paper by the EHD jet printing method based on the high-voltage electrostatic focusing lens. The effects of the working voltage, the velocity of the motion platform, and the flow rate of the injection pump on the width of the printed patterns were analyzed. Compared with the traditional EHD jet printing method, it has been verified that the EHD jet printing method based on the high-voltage electrostatic focusing lens has higher resolution under the same printing conditions, which provides a new method for achieving high-resolution pattern printing of PEDOT:PSS organic conductive polymer printing solutions. [ABSTRACT FROM AUTHOR]

Advanced micro/nano-flexible sensors, displays, electronic skins, and other related devices provide considerable benefits compared to traditional technologies, aiding in the compactness of devices, enhancing energy efficiency, and improving system reliability. The creation of cost-effective, scalable, and high-resolution fabrication techniques for micro/nanostructures built from optoelectronic materials is crucial for downsizing to enhance overall efficiency and boost integration density. The electrohydrodynamic jet (EHD) printing technology is a novel additive manufacturing process that harnesses the power of electricity to create fluid motion, offering unparalleled benefits and a diverse spectrum of potential uses for microelectronic printing in terms of materials, precision, accuracy, and cost-effectiveness. This article summarizes various applications of EHD printing by categorizing them as zero-dimensional (0D), one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) printing materials. Zero-dimensional (quantum dot) materials are predominantly utilized in LED applications owing to their superb optoelectronic properties, high color fidelity, adjustable color output, and impressive fluorescence quantum yield. One- and two-dimensional materials are primarily employed in FET and sensor technologies due to their distinctive physical structure and exceptional optoelectronic properties. Three-dimensional materials encompass nanometals, nanopolymers, nanoglass, and nanoporous materials, with nanometals and nanopolymers finding widespread application in EHD printing technology. We hope our work will facilitate the development of small-feature-size, large-scale flexible electronic devices via EHD printing. [ABSTRACT FROM AUTHOR]

Electrohydrodynamic jet (E‐Jet) printing is one of the most effective methods for fabricating micro/nanostructures due to its high‐resolution, broad material adaptability, and simple process. However, printing high‐resolution patterns on curved or insulated substrates still is of a great challenge because it is quite difficult to keep the electric field distribution stable between the nozzle and the substrate during the printing process. To address these issues, a dual‐ring electrostatic focused electrohydrodynamic jet (DEFEJ) printing method is proposed. In this technique, a microtip with a radius of curvature (ROC) of several micrometers is placed in a conductive dual‐ring structure to form the built‐in electrostatic focusing and drive the Taylor cone. The high‐speed jets then fall on the substrate due to their own motion inertia, eliminating the influence of the substrate curvature and its conductivity on the electric field distribution. Submicrometer droplets with an average diameter of about 0.83 µm are obtained using a 10‐µm‐ROC microtip. In addition, high‐resolution microstructure patterns are also printed on substrates with different conductivity and curvature. This DEFEJ printing method not only has the same printing accuracy as conventional E‐Jet printing, but also can significantly increase the adaptability of E‐Jet printing to different substrates. [ABSTRACT FROM AUTHOR]

Quantum dot (QD)/organic nanohybrids were developed to be utilized in electrohydrodynamic (EHD) jet‐printed QD‐LEDs. Side‐chain copolymer with elongated aliphatic thiol groups was newly introduced into the nanohybrids to coordinate the polymer chains with the QD surface. The QD‐LEDs with the nonohybrids showed a higher current efficiency over 4‐fold than that with a QD‐only active layer. EHD jet‐printing was independently performed up to 5µm pixel pitch on a substrate, resulting in a resolution of ca. 5,080 pixels per inch. [ABSTRACT FROM AUTHOR]

Electrohydrodynamic (EHD) printing is a cutting-edge micro/nano manufacturing technology for flexible substrates. Generally, EHD printing uses an electric field to drive droplet jet printing, which has characteristics of low cost, simple structure, and high precision. According to the research status of EHD printing at home and abroad, this article mainly focuses on the processing and applications of demanding devices by EHD printing, as well as the influence of associated-processing parameters, with regard to the breakthrough of different kinds of electronic inks developed in recent 5 years. Upon the understanding of the challenges and opportunities from the point of view of engineering applications, optimization strategies for ink selection are put forward for driving EHD printing in various fields of transistors, sensors, biomedicine, and electroluminescent devices.

This paper describes a fabrication method of a novel type of micro piezoelectric thick-film longitudinal-bending coupled (LBC) vibrator with a length of 8 mm and thickness of 0.34 mm using electrohydrodynamic jet (E-jet) printing. The LBC micro-vibrator was designed, and a frequency sensitivity analysis of the structural parameters was implemented. When the thickness of the lead zirconate titanate (PZT) thick-film element of the vibrator reached 76 μm, tuning of the composite-mode frequency consistency could be achieved. The micro-vibrator was then fabricated by depositing the PZT thick film directly on the surface of the elastic body using E-jet printing, and the film thickness was flexibly adjusted by tuning the number of prints, thus avoiding the problems of insufficient PZT thin film thickness (≤1 μm) and excessive bulk PZT ceramic volume. Micro-morphological observations showed that the printed thick film was dense and smooth, with a thickness of approximately 76 μm. Furthermore, the vibration mode frequency of the vibrator differed from the test resonant frequencies by only 0.92%, and the vibrator could achieve driving motion with a volume and an excitation voltage approximately one-tenth of that of a bulk piezoelectric motor. Moreover, the unit power density was 0.36 W kg−1 V−1, which is 1.6 times higher than that of a large bulk piezoelectric motor, indicating that the vibrator has good potential for small-space and low-voltage applications. [ABSTRACT FROM AUTHOR]

Terahertz metamaterials are some of the core components of the new generation of high-frequency optoelectronic devices, which have excellent properties that natural materials do not have. The unit structures are generally much smaller than the wavelength, so preparation is mainly based on semiconductor processes, such as coating, photolithography and etching. Although the processing resolution is high, it is also limited by complex processing, long cycles, and high cost. In this paper, a design method for dual-band terahertz metamaterials and a simple, rapid, low-cost metamaterial preparation scheme based on step-motor-driven electrohydrodynamic jet technology are proposed. By transforming an open-source 3D printer, the metamaterial structures can be directly printed without complex semiconductor processes. To verify effectiveness, the sample was directly printed using nano conductive silver paste as consumable material. Then, a fiber-based multi-mode terahertz time-domain spectroscopy system was built for testing. The experimental results were in good agreement with the theoretical simulation. [ABSTRACT FROM AUTHOR]

Electrohydrodynamic (EHD) jet printing of solvent-based inks or melts allows for the producing of polymeric fiber-based two- and three-dimensional structures with sub-micrometer features, with or without conductive nanoparticles or functional materials. While solvent-based inks possess great material versatility, the stability of the EHD jetting process using such inks remains a major challenge that must be overcome before this technology can be deployed beyond research laboratories. Herein, we study the parameters that affect the stability of the EHD jet printing of polyethylene oxide (PEO) patterns using solvent-based inks. To gain insights into the evolution of the printing process, we simultaneously monitor the drop size, the jet ejection point, and the jet speed, determined by superimposing a periodic electrostatic deflection. We observe printing instabilities to be associated with changes in drop size and composition and in the jet’s ejection point and speed, which are related to the evaporation of the solvent and the resulting drying of the drop surface. Thus, stabilizing the printing process and, particularly, the drop size and its surface composition require minimizing or controlling the solvent evaporation rate from the drop surface by using appropriate solvents and by controlling the printing ambient. For stable printing and improved jet stability, it is essential to use polymers with a high molecular weight and select solvents that slow down the surface drying of the droplets. Additionally, adjusting the needle voltages is crucial to prevent instabilities in the jet ejection mode. Although this study primarily utilized PEO, the general trends observed are applicable to other polymers that exhibit similar interactions between solvent and polymer.

A micron-scale bilayer sensor was fabricated in situ by electrohydrodynamic jet printing for detecting H 2 gas with highly selectivity, sensitivity and stability. The sensor consisted of a Pt loaded mesocellular silica foam (Pt-MCF) catalytic filter layer, and a ZnO/SnO 2 /Au (ZSA) sensing layer. Benefiting from the selective catalytic oxidation for CO in the catalytic filter layer, the cross-interference of CO on this sensor was reduced from 58 % to 15 %. The sensor also demonstrated a satisfactory selectivity to H 2 in interfering gases of CO 2 and CH 4 due to its high specific response to H 2. In the ZSA sensing layer, the n-n heterojunction (ZnO-SnO 2) and abundant active sites on the Undaria pinnitafida -like curved nanosheet structure effectively enhanced the response of H 2 by 6.7 times. The sensors exhibited a wide H 2 dynamic range of 0.5–500 ppm with low detection limit of 94 ppb. The response/recovery time to 50 ppm H 2 was 24 s/35 s. The sensor also showed good long-term stability in 28-day response-repeatability measurement (RSD=5.3 %) and good anti-humidity. [Display omitted] • A bilayer sensor was fabricated by EHD printing for selective detection of H 2. • The sensor consists of a Pt-MCF catalytic filter layer and a ZSA sensing layer. • Catalytic oxidation in filter layer reduces the cross-interference of CO. • The Undaria pinnitafida -like sensing layer improves the sensor sensitivity. • The sensor exhibits rapid response, satisfactory stability and anti-humidity. [ABSTRACT FROM AUTHOR]

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 144 μ m. 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 μ Wh 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. [Display omitted] • World-leading linewidth and h/w ratio in 3D MSCs based on direct printing. • All-printed 3D MSCs with homogeneous Ag interface across all layers including CC. • Precise 3D electrode structures without differentiation on flat and curved substrates. • Enhanced electrochemical property with C A of 763.1 mF cm−2 and E A of 256.6 μ Wh cm−2. • Successful application implementation on a curved surface by powering an LED bulb. [ABSTRACT FROM AUTHOR]

Metal‐based patterned conductors have a key role in flexible and curved micro/nanodevices. However, the fabrication of micro/nanoscale metal‐based electrodes with excellent electrical conductivities and well‐organized flexible/curved polymeric substrates remains a major challenge associated with a posttreatment. In this study, a maskless and direct‐writing method of electrohydrodynamic jet (e‐jet) printing combined with the conventional wet etching process is developed for fabrication of microscale conductive features of microstructure‐enhanced patterned electrodes without high‐temperature treatment. Customized metal‐patterned electrodes and various metal‐patterned electrode arrays are fabricated on a flexible/curved polyethylene terephthalate substrate. In addition, ultraviolet‐curable hierarchical micro/nanostructures can be fabricated by stable cone‐jet and electrospray modes. The results of electrocardiography (ECG) and electromyography signal measurements show that the added microstructures can increase the contact between the metal microelectrodes and skin surface, which yield lower disturbance and baseline drift and enable a stable ECG signal acquisition. Overall, e‐jet printing is a promising mask‐free approach for fabrication of conductive metal patterns for flexible and stretchable devices. [ABSTRACT FROM AUTHOR]

Electrohydrodynamic jet (e‐jet) printing technology overcomes some limitations such as the viscosity and resolution of the traditional ink‐jet printing by breaking surface tension of the droplets with high voltage and the formation of Taylor cone. The technique is becoming more and more popular because it can be widely used in the fabrication of the conductive line of electronics, electrode, transistor, sensor, and other electronics as microelectrode, microlen, and heater. This review provides insight into the effect of the influence factors such as voltage, speed, nozzle, jetting ink characteristics, and the representative conductive materials of the ink as metal nanoparticles (NPs) and carbon materials, or organic conductive polymers on the fabrication of the different electronics by the e‐jet printing technology. Specially, the characteristics of different resultant electronics are compared and the possible mechanisms are analyzed. Finally, the challenge and development trend of the e‐jet printing technology are discussed, which will shed a light on the fabrication of the next‐generation flexible electronics with better performance. [ABSTRACT FROM AUTHOR]

Here, we suggest simple method for multi value slope In‐Ga‐Zn O (IGZO) thin‐film transistors (TFTs) using electrohydrodynamic (EHD) jet printing. To induce multi value slope, parasitic channel was intentionally formed on top of IGZO main channel using EHD jet printing. By precisely controlling parasitic channel regime with EHD jet printing, multi value slope could be realized without degradation in electrical performance of original IGZO TFTs. [ABSTRACT FROM AUTHOR]

• A novel E-Jet 3D printing method was proposed for fabricating PZT nano-hair. • The resultant effects of rotating electrohydrodynamic force and thermal radiation was employed, which extricated from the traditional electrohydrodynamic effect. • The 3D printing process of PZT nano-hair had the characteristics of controllability, fast and scalability. • The printed PZT nano-hair with ultrahigh aspect ratio feature exhibited excellent mechanical properties and electro-mechanical coupling properties. Micro/nanoscale hairs found in living organisms combine many inspiring properties such as miniaturization, low power consumption, adaptability, and the sensing of signals. Mimicking these excellent biological hairs provided an effective way to develop advanced artificial sensing sensors. Here, a printed bioinspired piezoelectric nano-hair with ultra-high sensitivity was developed for airflow detection. A novel nanoscale electrohydrodynamic jet 3D printing method was developed to fabricate PZT nano-hair with controllability, fast, and inexpensive characteristics. Various PZT nano-hairs down to the scale of 200 nm with high aspect ratio features of 523 were directly printed. Herein, the printed PZT nano-hair exhibited pure perovskite structures, excellent mechanical properties, and a high piezoelectric coefficient. This bioinspired PZT hair sensor demonstrated that the novel printed PZT hair airflow sensor showed ultra-high detection sensitivity to low-speed airflow (0.02 m s−1). This novel nanoprinting strategy and the printed PZT nano-hair indicate the development of functional nanostructures inaccessible by traditional manufacturing methods. [ABSTRACT FROM AUTHOR]

A micron-scale bilayer H 2 S sensor fabricated by electrohydrodynamic (EHD) jet printing in situ was evaluated. The prepared sensor consisted of a Pd@TiO 2 cover layer (porous catalytic sensing layer), a SnO 2 bottom layer (electron transport layer) and a Sn-Ti transition layer between them. The addition of TiO 2 nanoparticles to the cover layer led to a porous structure after one-step sintering. The increase in specific surface area and the formation of heterojunction effectively improved the sensor sensitivity. The PdO nanoparticles loaded on the surface of TiO 2 nanoparticles further improved the performance due to its catalysis. Since the kinetic energy of droplets of the same size generated by EHD inkjet printing is about 48 times that of inkjet printing, the film density is much higher than that of inkjet printing. The relatively dense bottom layer, and the thick and stable transition layer improved the long-term stability of the sensor. The detection limit of the sensor is 6 ppb, with linear range of 0.02–10 ppm H 2 S. The response and recovery times are 7 s and 45 s (2 ppm H 2 S), respectively. After 9 months of intermittent measurement, the response of the sensor to 2 ppm H 2 S decreased by only 10.6%. [Display omitted] • A SnO 2 -based bilayer H 2 S sensor prepared by EHD printing shows high stability. • The addition of TiO 2 nanoparticles in catalytic layer makes it highly porous. • The porous and stable catalytic layer generate high sensitivity and fast response. • The Sn-Ti transition layer ensures the long-term stability of the sensor. [ABSTRACT FROM AUTHOR]

Terahertz metamaterials are some of the core components of the new generation of high-frequency optoelectronic devices, which have excellent properties that natural materials do not have. The unit structures are generally much smaller than the wavelength, so preparation is mainly based on semiconductor processes, such as coating, photolithography and etching. Although the processing resolution is high, it is also limited by complex processing, long cycles, and high cost. In this paper, a design method for dual-band terahertz metamaterials and a simple, rapid, low-cost metamaterial preparation scheme based on step-motor-driven electrohydrodynamic jet technology are proposed. By transforming an open-source 3D printer, the metamaterial structures can be directly printed without complex semiconductor processes. To verify effectiveness, the sample was directly printed using nano conductive silver paste as consumable material. Then, a fiber-based multi-mode terahertz time-domain spectroscopy system was built for testing. The experimental results were in good agreement with the theoretical simulation.

Despite the appealing technical advantages of printed electronic (PE) technologies, there are very few studies on their technical maturity. Conductive materials are the primary substances used in PEs; therefore, electromigration (EM) is an important reliability aspect of printed conductive patterns. The inevitable porous nature of the printed lines is derived from the nanoparticle-dispersed inks and is a major concern for the EM reliability. Electromigration has been identified as the primary failure mode of interconnect lines used in semiconductor-integrated circuits. Electromigration is a high-current-density-induced mass transport phenomenon that manifests as voids, hillocks, and/or open circuits because of momentum exchange between the conduction electrons and host metal atoms in an external electric field. High temperature and current density accelerate damage, thereby increasing line resistance and reducing circuit lifetime. This study involves investigation of the EM characteristics of Ag lines patterned by using the electrohydrodynamic (EHD) printing technique based on the resistometric and Black theoretical models. It was observed that ion migration was directed toward the cathode for EHD-printed Ag lines, indicating that the electric field–ion interactions (direct force) dominated over the momentum transfer by the electron–ion interactions (wind force). The activation energy for EM in the EHD-printed lines indicates that the surface diffusion is critical to EM failure mechanism. This study is a pioneering work on characterizing the EM performance of the EHD-printed Ag lines and the EM failure mechanism. [ABSTRACT FROM AUTHOR]

Electrohydrodynamic (EHD) jet printing is an emerging technique in the field of additive manufacturing. Due to its versatility in the inks it can print, and most importantly, the printing resolution it can achieve, it is rapidly gaining favor for application in the manufacture of electronic devices, sensors, and displays among others. Although it is an affordable and accessible manufacturing process, it does require excellent operational understanding to achieve high resolution printing of up to 50 nm as reported in literature. In this review, three main aspects are considered, namely, the ink properties, the printer system itself (including design, nozzle dimensions, applied potential, and others), and the substrate onto which printing is being carried out. Knowing how all these factors can be manipulated and brought together allows the users of EHD printing to achieve extraordinary resolution and consistent results. The review is concluded with a brief discussion on where one can see the potential for development in this field of research. [ABSTRACT FROM AUTHOR]

Electrohydrodynamic (EHD) jet printing is an emerging technique in the field of additive manufacturing. Due to its versatility in the inks it can print, and most importantly, the printing resolution it can achieve, it is rapidly gaining favor for application in the manufacture of electronic devices, sensors, and displays among others. Although it is an affordable and accessible manufacturing process, it does require excellent operational understanding to achieve high resolution printing of up to 50 nm as reported in literature. In this review, three main aspects are considered, namely, the ink properties, the printer system itself (including design, nozzle dimensions, applied potential, and others), and the substrate onto which printing is being carried out. Knowing how all these factors can be manipulated and brought together allows the users of EHD printing to achieve extraordinary resolution and consistent results. The review is concluded with a brief discussion on where one can see the potential for development in this field of research.

Electrohydrodynamic (EHD) jet printing is a widely employed technology to create high-resolution patterns and thus has enormous potential for circuit production. However, achieving both high conductivity and high resolution in printed polymer electrodes is a challenging task. Here, by modulating the aggregation state of the conducting polymer in the solution and solid phases, a stable and continuous jetting of PEDOT:PSS is realized, and high-conductivity electrode arrays are prepared. The line width reaches less than 5 μm with a record-high conductivity of 1250 S/cm. Organic field-effect transistors (OFETs) are further developed by combining printed source/drain electrodes with ultrathin organic semiconductor crystals. These OFETs show great light sensitivity, with a specific detectivity ( D *) value of 2.86 × 10 14 Jones. In addition, a proof-of-concept fully transparent phototransistor is demonstrated, which opens up new pathways to multidimensional optical imaging.

Microlens arrays (MLAs) have been widely employed as key components of various functional devices. However, the high‐efficiency fabrication of tailored MLAs with high numerical aperture (NA) is still a challenge. Herein, a one‐step maskless fabrication method of MLAs on polydimethylsiloxane (PDMS) nanofilm modified substrate via microtip focused electrohydrodynamic jet (MFEJ) printing is developed. The MFEJ printing can effectively avoid nozzle blockage even with highly viscous UV‐curable polymer. The contact angle (CA) of polymer can be controlled on different hydrophobic substrates, which are modified by treatment with PDMS, and MLAs with different NA can be realized. The polymer CA increases from 19° to 73° after surface modification, and the NA of MLAs correspondingly increases from 0.18 to 0.53. The MLAs diameter and focusing properties can be easily tuned by combining the printing parameters with PDMS nanofilm modification. Various patterns of MLAs with high NA are obtained by MFEJ printing. The projection experiment indicates the uniformity and excellent optical performance of the MLAs. Moreover, the fabricated MLAs can generate magnified virtual images with a magnification up to 1.72‐fold. Results show that the MFEJ printing can fabricate functional and tailored MLAs with high NA on the PDMS nanofilm‐modified substrate. [ABSTRACT FROM AUTHOR]

Peripheral nerve injury is a common clinical problem often requiring surgical nerve reconstruction. To this end, tissue-engineered conduit has been proved to be crucial for nerve reconstruction. Despite its progress in recent years, the design and fabrication of translational biomimetic nerve conduits is highly challenging. Therefore, this study aims to design and fabricate mechanically-tunable nerve conduits with biomimetic structural features of the human nerve suitable for nerve tissue engineering. Herein, we employed combinatorial approach comprising of electrohydrodynamic (EHD) jet printing, dip-coating, and electrospinning techniques for fabricating triple-layered conduits. The intricate structural details were achieved via high-resolution EHD jet printed PCL filaments with tunable directionality, as the innermost layer; followed by dip coating of gelatin hydrogels to form the middle layer, and lastly, wrapped with electrospun PCL nanofibers as an outer layer of the conduits. The mechanical properties, porosity, and biocompatibility of the fabricated conduits were studied and compared with control. The results of this study confirmed that the combinatorial approach has greater potential to fabricate mechanically-tunable triple-layered conduits with favorable neuronal precursor and vascular cell compatibility. [ABSTRACT FROM AUTHOR]

Over the past few decades, electrohydrodynamic (EHD) printing has proved to be an environmentally friendly, cost-effective and powerful tool in manufacturing electronic devices with a wire width of less than 50 μm. In particular, EHD printing is highly valued for the printing of ultrafine wire-width silver electrodes, which is important in manufacturing large-area, high-resolution micron-scale or even nanoscale structures. In this paper, we compare two methods of surface modification of glass substrate: UV treatment and oxygen plasma treatment. We found that oxygen plasma was better than UV treatment in terms of wettability and uniformity. Secondly, we optimized the annealing temperature parameter, and found that the conductivity of the electrode was the highest at 200 °C due to the smoothing silver electrode and the oxidation-free internal microstructure. Thirdly, we used EHD printing to fabricate silver electrodes on the glass substrate. Due to the decrease of conductivity as a result of the skin effect and the decrease of silver content, we found that driving voltage dropped, line width decreased, and the conductivity of silver line decreased. After the optimization of the EHD printing process, Ag electrode line width and conductivity reached 19.42 ± 0.24 μm and 6.01 × 106 S/m, demonstrating the potential of electro-hydraulic printing in the manufacturing of flexible, wearable, high-density, low-power-consumption electronics.

Direct patterning of copper (Cu) electrodes through a noncontact electrohydrodynamic (EHD) jet printing process is developed to overcome the drawback of printing mechanisms such as high viscosity in inkjet printing. Printed Cu lines with a width of about 40 μm are obtained from Cu paste with a viscosity of 4000 cPs using an additive. The effect of the operating parameters on jetting modes and printed patterns is investigated. The electrical property of the printed Cu layer shows a low resistivity of 8 × 10−4 Ωm after sintering under vacuum compared with air annealing. Solution‐processed zinc tin oxide (ZTO) thin‐film transistors (TFTs) with vacuum‐annealed Cu source and drain (S/D) electrodes are fabricated with comparable characteristics, such as an average effective mobility in the saturation region (μ) of 0.50 cm2 V−1 s−1, an on‐to‐off current ratio (Ion/Ioff) of 5.5 × 105, and a subthreshold slope (SS) of 3.35 V decade−1. These results demonstrate the potential of EHD jet‐printed Cu for application in electronic devices. [ABSTRACT FROM AUTHOR]

Low-cost, safe, and environmental-friendly rechargeable aqueous zinc-ion batteries (ZIBs) are promising as next-generation energy storage devices for wearable electronics among other applications. However, sluggish ionic transport kinetics and the unstable electrode structure during ionic insertion/extraction hamper their deployment. Herein, a new cathode material based on a layered metal chalcogenide (LMC), bismuth telluride (Bi 2 Te 3 ), coated with polypyrrole (PPy) is proposed. Taking advantage of the PPy coating, the Bi 2 Te 3 @PPy composite presents strong ionic absorption affinity, high oxidation resistance, and high structural stability. The ZIBs based on Bi 2 Te 3 @PPy cathodes exhibit high capacities and ultra-long lifespans of over 5000 cycles. They also present outstanding stability even under bending. In addition, here the reaction mechanism is analyzed using in situ X-ray diffraction, X-ray photoelectron spectroscopy, and computational tools and it is demonstrated that, in the aqueous system, Zn 2+ is not inserted into the cathode as previously assumed. In contrast, proton charge storage dominates the process. Overall, this work not only shows the great potential of LMCs as ZIB cathode materials and the advantages of PPy coating, but also clarifies the charge/discharge mechanism in rechargeable ZIBs based on LMCs., (© 2023 Wiley-VCH GmbH.)

An electrohydrodynamic jet (EHD) printing process was optimized for the patterning of an indium tin oxide (ITO) nanoparticles ink by manipulating its surface tension through the addition of a nonionic surfactant, Triton X-100 (TX-100). As a result, a stable cone-jet mode was performed, which could provide printed drops with the smallest diameter and printing fidelity among EHD jet printing modes, and lead to a line width ranging from 230 µm to 30 µm in addition to well-define patterns with various shapes for ITO transparent conducting electrodes (TCEs). The multi-printing technique and subsequent thermal annealing for printed ITO TCEs allows improvement in its electrical conductivity. In addition, the evolution of the chemical composition and crystalline structure of the printed ITO TCE according to the annealing temperature was investigated to determine the optimal conditions to utilize printed ITO nanoparticles for ZnO-based thin-film transistors. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Silver nanowires penetrated through paper's thickness for making 3D interconnects. • High viscosity silver nanoparticles dispensed on paper reveal no penetration. • 3D circuitry in single sheet of paper printed using double-sided EHD jet printing. • Two-dimensional droplet actuation achieved on a paper-based digital microfluidics. • Cellphone-based colorimetric detection of methyl paraoxon from 10 to 100 μM concentration. Abstract Double-sided electrohydrodynamic jet printing of circuitry using silver nanowires (AgNWs) and dispensing of high viscosity silver nanoparticles (AgNPs) is demonstrated for the first time in the fabrication of a two-dimensional array of electrodes (3D circuitry) on a single sheet of paper. The penetration of AgNW ink through the paper's thickness by capillary imbibition allows for multilayer electrical access to connect the individual electrodes. This makes it an automated and efficient choice as the functional area of the device is conserved and the surface of the paper is preserved. This allows for two-dimensional droplet manipulation on a paper-based digital microfluidics (PBDMF) platform. Compared to printed circuit board technology, paper-based electronics offer a range of desirable properties: they are light weight, portable, economical, flexible, biodegradable, and the materials are abundantly available. The fabricated PBDMF chip is demonstrated to be a low-cost, fully reconfigurable, and disposable point-of-care diagnostic platform for the environmental sensing of pesticide using organophosphorus hydrolase enzyme through colorimetric detection via smartphone. [ABSTRACT FROM AUTHOR]

Abstract Microscale additive manufacturing μ -AM processes are a class of manufacturing processes used to fabricate micron-sized structures in a sequence of direct additions of materials as instructed by a digital file, as opposed to the lithographic patterning and subtractive etching used in traditional microscale manufacturing. Despite being sophisticated, numerically controlled tools, material addition is an open-loop process which requires continual user intervention to heuristically tune process parameters. This paper details the first experimental demonstration of a run-to-run feedback algorithm termed Spatial Iterative Learning Control (SILC), a framework previously introduced by the authors to enable robust, auto-regulation of sensitive μ -AM processes [1, 2]. We demonstrate that SILC enables us to autonomously fabricate complex topography structures with as small as 5 µm x - and y -axis resolution and ∼ 113 nm feature height accuracy, without any heuristic tuning by a user. Lastly, it was observed that an SILC design was robust to system faults, as demonstrated by the ability to recover from both an actuator and sensor fault in two iterations. [ABSTRACT FROM AUTHOR]

Abstract Integrated metrology is critical for quality control and validation of micro-scale additive and subtractive manufacturing processes. However, the current practice in micro-scale additive manufacturing is to manufacture a component on a die and then transfer the die to a separate metrology tool, losing the datum, increasing production time, and also risking contamination. This paper presents a new system that integrates electrohydrodynamic jet printing, an emerging micro-scale additive manufacturing technique, with inline atomic force microscopy for rapid, die-by-die in-line metrology and quality monitoring. The system performs automatic registration of datums and is self-contained for minimal contamination. To validate the effectiveness of the integrated system, performance metrics such as position precision and accuracy and drop volume precision are derived from 50 samples of a 122-drop pattern. These experimental results provide a demonstration of electrohydrodynamic jet printed patterns with completely automated, in situ quality monitoring. [ABSTRACT FROM AUTHOR]

Solution-processable electrochromic (EC) materials have been investigated widely for various applications, such as smart windows, reflective displays, and sensors. Among them, tungsten trioxide (WO3) is an attractive material because it can form a film via a solution process and relative low temperature treatment, which is suitable for a range of substrates. This paper introduces the slot-die and electrostatic force-assisted dispensing (EFAD) printing for solution-processable methods of WO3 film fabrication. The resulting films were compared with WO3 films prepared by spin coating. Both films exhibited a similar morphology and crystalline structure. Furthermore, three different processed WO3 film-based electrochromic devices (ECDs) were prepared and exhibited similar device behaviors. In addition, large area (100 cm2) and patterned ECDs were fabricated using slot-die and EFAD printing. Consequently, slot-die and EFAD printing can be used to commercialize WO3 based-ECDs applications, such as smart windows and reflective displays.

This talk includes an overview of high‐resolution electrohydrodynamic(EHD) jet printing method for display. With the EHD jet printing method, ones could overcome some limitations of conventional inkjet printing such as ink viscosity and pattern resolution. On the other hand, to eject drops by the EHD method, an electrode should supply charge to the ink so that there is possibility of electro‐chemical reaction on the electrode in a nozzle. Here, we present novel technology to prevent from the electro‐chemical reaction, which is named as induced‐EHD method. We present several research results for display applications such as fabrication of 1µm width electrode for thin film transistor(TFT), patterning quantum, and patterning pads for micro‐LED display. [ABSTRACT FROM AUTHOR]

Electrohydrodynamic jet (E-Jet) printing technology provides unmatched advantages in the fabrication of patterned micro/nanostructures. However, the rapid jets generated during printing can lead to localized droplet accumulation on complex structures due to the relatively slow motion control achieved with motorized translation stages, resulting in distorted patterns. To address this challenge, we introduce two jet-deflecting electrodes orthogonally placed on each other, which can rapidly change the electric field in the vicinity of the jet and thus flexibly adjust the flight trajectory of the fast jet to avoid the region where droplets have been deposited. In this way, the jet droplets are precisely controlled to generate high-fidelity microstructures with arbitrary predefined patterns on the stationary substrate. The maximum deflection distance of the jet droplets reaches several hundred microns. Furthermore, the positioning error of the printed structure is less than 3%. Moreover, we successfully obtained a diverse range of complex patterns by combining this technique with stage motion. This innovative printing technology not only enables the fabrication of complex patterned structures with high fidelity but also opens up exciting possibilities for new applications that require complete control of fast droplet positioning.

Abstract AgNWs-based electrodes were directly patterned using an electrohydrodynamic (EHD) jet printing technique. We investigated EHD jet printing for AgNWs ink in detail, and established the optimum printing conditions in dragging mode for controlling the dimensions and conductivity of the AgNWs network, although the cone-jet printing mode has been the most conventionally used mode for EHD jet printing. The printed AgNWs were used as source/drain (S/D) electrodes of an organic thin film transistor (OTFT) with bottom-contact geometry, and yielded an average field-effect mobility (μ FET), threshold voltage (V th) and on/off current ratio (I on / I off) of 0.48 cm2/V, −11.2 V, and ∼106, respectively. In addition, we investigate the interface morphologies between pentacene and AgNWs S/D electrode to figure out charge carrier injection property of AgNWs S/D electrode, by comparing vacuum-deposited Au ones. Graphical abstract Image 1 Highlights • We investigated electrohydrodynamic (EHD) jet printing for silver nanowires (AgNW) ink. • The optimum printing mode can control the dimensions and conductivity of AgNW network. • EHD-jet-printed AgNWs were used as the electrodes of pentacene OTFTs. • AgNW-based OTFTs showed a μ FET of 0.48 cm2/V, 100 times that of gold-based OTFTs. [ABSTRACT FROM AUTHOR]

Efforts to directly printing nanoscale patterns by electrohydrodynamic jet for demanding device applications in electronics, medicine, and biotechnology have grown rapidly in recent years. However, printing of nano-patterns significantly depends on the fabrication of nanoscale nozzles. Here, we describe a low-cost and concise method for fabrication of SU-8 nano-nozzles only based on traditional UV photolithography. By this method, thermal and volume-shrinkage induced nanoscale crack can be automatically formed due to stress release after developing step. The influence of material, SU-8 layer thickness, and exposing duration on the stress in the SU-8 layer was analyzed to fabricate straight and long nano-crack. The result shows that the suitable material, SU-8 layer thickness, and exposing duration are silicon, 70 µm, and 46 s, respectively. Under the optimized condition, 60 µm long nano-crack with width of 250 nm and depth of 20 nm can be fabricated. The fluorescence image demonstrates the absence of blocking and leakage over the entire nano-crack. [ABSTRACT FROM AUTHOR]

An electrohydrodynamic (EHD) jet printing technique was used for direct printing of a conductive polymer combined with carbon nanotubes (CNT). The solutions mixture of poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) and carbon nanotubes (CNTs) wrapped with PSS served as a PEDOT:PSS/CNT composite ink for the EHD jet printing. The EHD jet-printed patterns of the PEDOT:PSS/CNT composite exhibited excellent dimensional stability and provided sub-10-micrometer channel lengths suitable for highly integrated organic thin-film transistors (OTFTs). The resulting pentacene OTFTs employing the channel length of 7 μm yielded the field-effect mobility of 0.03 ± 0.01 cm 2 /(V s). In addition, we investigated the electronic structure and the crystalline morphology at the interface between pentacene and the PEDOT:PSS/CNT composite electrode, as well as the contact resistance of the OTFTs by varying the channel length produced by the EHD jet printing process. [ABSTRACT FROM AUTHOR]

Electrohydrodynamic jet (E-Jet) is an approach to the fabrication of micro/nano-structures by the use of electrical forces. In this process, the liquid is subjected to electrical and mechanical forces to form a liquid jet, which is further disintegrated into droplets. The major advantage of the E-Jet technique is that the sizes of the jet formed can be at the nanoscale far smaller than the nozzle size, which can realize high printing resolution with less risk of nozzle blockage. The E-Jet technique, which mainly includes E-Jet deposition and E-Jet printing, has a wide range of applications in the fabrication of micro/nano-structures for micro/nano-electromechanical system devices. This technique is also considered a micro/nano-fabrication method with a great potential for commercial use. This study mainly reviews the E-Jet deposition/printing fundamentals, fabrication process, and applications. [ABSTRACT FROM AUTHOR]

In this study, polycaprolactone/mineral trioxide aggregate (PCL/MTA) scaffolds were successfully fabricated via an electrohydrodynamic jet (or E-jet) 3D printing system developed by our group. The viscosity of the composited solutions and the key process parameters (i.e. applied voltage and feed rate) were investigated to achieve an optimal process condition. To investigate the potential of PCL/MTA scaffolds to support regeneration ability for dentin related tissue, we seeded dental pulp stem cells on the scaffolds, and compared the results with cell-seeded PCL scaffolds. Assessment of cell viability and proliferation using live/dead cell staining and MTS assay showed compatibility of PCL and PCL/MTA scaffolds for cellular attachment and growth. These scaffolds could be used for fabrication of three-dimensional tissues and in future could be applied to dentin and periodontal tissue engineering applications.

Droplet generation process can directly affect process regulation and output performance of electrohydrodynamic jet (E-jet) printing in fabricating micro-to-nano scale functional structures. This paper proposes a numerical simulation model for whole process of droplet generation of E-jet printing based on the Taylor-Melcher leaky-dielectric model. The whole process of droplet generation is successfully simulated in one whole cycle, including Taylor cone generation, jet onset, jet break, and jet retraction. The feasibility and accuracy of the numerical simulation model is validated by a 30G stainless nozzle with inner diameter ~160 μm by E-jet printing experiments. Comparing numerical simulations and experimental results, period, velocity magnitude, four steps in an injection cycle, and shape of jet in each step are in good agreement. Further simulations are performed to reveal three design constraints against applied voltage, flow rate, and nozzle diameter, respectively. The established cone-jet numerical simulation model paves the way to investigate influences of process parameters and guide design of printheads for E-jet printing system with high performance in the future.