How can micro/nano-scale devices be industrially produced on flexible substrates?

Electrohydrodynamic (EHD) printing is an advanced additive manufacturing process that utilizes a high-voltage electric field between the nozzle and the substrate to create nanoscale structures, especially for fabricating on flexible or non-flat substrates, as well as for producing large-aspect-ratio micro/nanostructures and composite multi-material structures. Nevertheless, EHD printing remains non-industrialized due to low productivity, which is attracting increasing attention.

Published in International Journal of Extreme Manufacturing, Prof. Hongbo Lan and his team provide a detailed review of the latest advancements in multi-nozzle EHD printing technology, which significantly increases productivity and represents one of the most promising directions for EHD technology to achieve large-scale industrialized production.

This review discusses the crosstalk effect as an entry point, providing the reader with a detailed account of the mechanism of jet motion and the formation of the electric field crosstalk effect under multi-nozzle condition. It also discusses several widely used inhibition methods. Additionally, it summarizes the fabrication of various multi-nozzle EHD printheads as well as demonstrates applications, such as nano-counterfeit labels and finger motion sensors, prepared using this technology.

As a novel technology, multi-nozzle EHD printing utilizes electric field forces to stretch printing inks, enabling the formation of nanostructures through high-voltage electric fields. This technique employs multiple nozzles, each connected to an independently supplied ink reservoir, which increases the number of deposition channels for the solution. During the deposition process, the solutions from different nozzles intertwine, allowing for the creation of phase-change materials that exhibit the properties of multiple materials within a single structure.

However, due to the characteristics of the electric field, the charge distribution and jet pattern at the nozzle tip vary depending on the number of nozzles. When multiple nozzles are arranged in an array structure, the electric field strength at the nozzle tip becomes unevenly distributed, resulting in a shift in the jet and the occurrence of multiple nozzle electric field crosstalk. Additionally, manufacturing high-precision, consistent multi-nozzle systems is relatively challenging. This difficulty is a key factor that restricts their full development.

Therefore, overcoming the limitations of multi-nozzle EHD printing is the primary focus of this research topic.

“The impact of the crosstalk phenomenon can be effectively mitigated by designing an appropriate electric field distribution and intensity,” said Prof. Lan, “Depending on the jet pattern, the multi-nozzle system can be optimized by introducing auxiliary electrodes, modifying the nozzle configuration, and reducing the charge distribution.”

Regarding the challenge of high-precision multi-nozzle printheads manufacturing, Prof. Zhang stated, “To manufacture these printheads, we can utilize deep reactive ion etching, rapid laser micromachining, wet etching, and other micromachining processes; however, producing high-density, high-consistency printheads remains a significant challenge.”

The team remains optimistic despite the challenges that lie ahead for multi-nozzle EHD printing technology.

“It provides a promising industrial solution that offers high efficiency in terms of accuracy, resolution, material usage, and cost,” said Prof. Lan, “Several companies are already implementing technology in factories to produce customized flexible display components. In the future, research will focus on crosstalk suppression, independent control of printheads, multi-material printing, printhead multiplexing, and digital control. These advancements aim to reduce the manufacturing costs of functional devices at the micro- and nanoscale, including tissue engineering, flexible displays, and body sensors.”

About IJEM:

International Journal of Extreme Manufacturing (IF: 16.1, consecutive 1st in the Engineering, Manufacturing category) is a multidisciplinary and double-anonymous peer-reviewed journal uniquely publishing original articles and reviews of the highest quality and impact in the areas related to extreme manufacturing, ranging from fundamentals to process, measurement, and systems, as well as materials, structures, and devices with extreme functionalities.

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