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.

It is attractive and challenging to fabricate micro-nano scale patterns in large area by parallel electrohydrodynamic jet printing (E-jet printing) with nozzle array. However, cross-talk effect (i.e. interference phenomenon) between nozzles may probably lead to poor positioning accuracy and cause jet instability. In this paper, design and evaluation of a special linear nozzle array with double auxiliary electrodes at both ends were proposed to restrain the cross-talk effect. Firstly, the numerical simulation model of multi-nozzle E-jet printing was established considering with electro-hydraulic coupling effect. The corresponding multi-nozzle E-jet printing processes in several geometry configurations were successfully simulated based on a commercial multi-physical software ‘COMSOL’. Secondly, the unique design of new type linear nozzle array with double auxiliary electrodes was proposed after accomplishing theoretical analysis and comparison study of simulation results. Thirdly, several experiments were carried out on a constructed multi-nozzle E-jet printing system to verify feasibility and effectiveness of the provided design. The experiments show that the proposed manner has obvious advantages in restraining cross-talk compared with traditional suppressing method ‘with single flat-head auxiliary electrode at both ends’. When nozzle space is 0.5 mm, the jet deflection angle 2.8° and Taylor cone angle 3.3° could be reduced to 0° and 0.05° with two methods respectively. Finally, the printability of fabricated new multi-nozzle was also characterized. Microscale droplets array (mean diameter about 200–240 μ m) could be achieved with no deflection and the gap between them is equal with the distance between adjacent nozzles. This study can provide a reference for the design of high integrated printhead and E-jet printing system.

Flexible electronic devices, such as flexible displays, sensors, and thin-film solar cells, are defined by their thinness, expansive surface area, precision, and elasticity, demonstrating significant applications in optoelectronics, information technology, healthcare, and energy sectors. With ongoing industrial innovation and evolution, diverse heterogeneous flexible electronic devices have arisen, necessitating substantial progress in material adaptability, structural design innovation, and manufacturing techniques. Traditional manufacturing processes commonly face difficulties in simultaneously achieving preparation accuracy, efficiency, and the integration of heterogeneous components. This constraint impedes the vigorous advancement of the flexible electronics sector. A synergistic combination of diverse manufacturing processes, along with the upgraded collaborative development of manufacturing equipment, may provide a feasible solution. Currently, flexible electronics in China are addressing industry challenges and exhibiting remarkable research dynamism and industrial innovation. The study begins with an overview of industry and academic research in the field and explores the contributions of Chinese researchers in solving production challenges. Finally, it showcases domestically produced manufacturing equipment for various process types, aiming to consolidate Chinese flexible electronics-related resources and provide a comprehensive reference for future research.

Flexible transparent electrodes (FTEs) have attracted much attention due to their advantages of excellent optical/electrical conductivities and good mechanical fatigue strength. However, their fabrication presents several challenges, including fabricating wires with high aspect ratio and sufficient tensile resistance. In this study, an embedded Ag/Cu metal-mesh FTE with a high figure of merit 24708 (sheet resistance 0.08 Ω/sq and 83.4% optical transmittance) is fabricated through the proposed method called self-confined electrohydrodynamic printing and selective electroplating of Cu. This method employs structured surfaces and patterned hydrophilic/hydrophobic properties to enable highly controllable deposition of solutions (e.g., positioning, line width, consistency), allowing the complete filling of imprinted microgrooves with a high aspect ratio of 2 (e.g., 4 μm width and 8 μm depth) with Ag/Cu metal. Moreover, the resulting FTEs demonstrate good resistance stability under repetitive bending and stretching and exhibit excellent performance in flexible transparent heaters and electromagnetic shielding films.

Spiral fibre has strong flexibility and high porosity, which can be widely used in fabrication of stretchable microelectrode for flexible electronics when functional materials are mixed in fibre. It is attractive and challenging to generate spiral fibre on plastic substrate in a controllable manner. In this paper, polyethylene oxide spiral fibres are successfully fabricated on PET substrate by electrospinning direct-writing. The whole fabrication process of one spiral fibre is observed by a high-speed camera at 10000 fps in order to reveal the internal mechanism. Influence of repulsive forces by remaining electric charges on substrate is the main cause for the unique spiral pattern. This can provide a reference for manufacturing of functional microelectrode in future.

Printhead with integrated electrodes plays an important role in electrohydrodynamic jet (E-jet) printing, which can remove the effect of substrate and may be potentially used in fabrication of microelectrodes for flexible electronics. In this paper, we propose a printhead with integrated electrodes to achieve E-jet printing on insulating substrate. Evaluation of the printhead is performed by E-jet printing tests of ethylene glycol in order to validate correctness of design and feasibility of printing on insulating substrate. The printing tests on silicon indicate that the design of proposed printhead with integrated electrodes is correct which can work normally. However, influence of repulsive force by remaining electric charges on substrate is the main cause for failure tests on PET substrate. This research can provide a lesson to implement E-jet printing on insulating substrate in future.