Application Cases

Experiment Name: Development of a Microstructured Electrohydrodynamic Jet Printing Platform on Insulating Substrates

Test Purpose: Electrohydrodynamic (EHD) jet printing technology holds significant application prospects and potential for its ability to fabricate microstructures on insulating/flexible substrates over large areas and at low costs. However, existing technologies still face challenges in fabricating microstructures on insulating substrates thicker than 3mm. Therefore, it is necessary to develop an EHD jet printing platform that can realize microstructure fabrication on large-area insulating substrates. The main purpose of the experiment is to design and manufacture an alternating current (AC) field printing nozzle and nozzle fixture based on the AC field printing method for insulating substrates, develop a displacement platform, integrate an observation camera, and write driving software to develop an EHD jet printing platform for insulating substrates. Applying a stable AC field to the EHD printing nozzle is crucial for printing on insulating substrates. An insulating substrate printing nozzle was developed, and the positional relationship between the nozzle and the grounded electrode was determined. To enhance the coordinated control of each module of the insulating printing device, the motion, imaging, liquid supply, and other modules were integrated, and a control program was written based on LabVIEW software to achieve the integration of the high-insulating substrate EHD jet printing platform.

Testing Equipment: High-voltage amplifier, function generator, EHD nozzle, host computer, camera, etc.

Experiment Process:

Figure 1: Schematic Diagram of the EHD Jet Printing Platform

The developed EHD jet printing platform for insulating substrates mainly includes driving software and hardware, as shown in Figure 1. The functional modules of the EHD jet printing platform are mainly composed of five parts.

(1) EHD Printing Nozzle Module

In the EHD printing process, the conductive ink printed on the substrate carries a certain concentration of residual charge. When the material accumulates on a metal electrode, the concentration of residual charge also increases. The polarity of the residual charge is the same as that of the charge on the surface of the conical jet, and the Coulomb repulsion between like charges can destabilize the jet, causing printing interruptions, whipping, and even nozzle clogging.

(2) Flow Supply Module

The surface tension of silver conductive ink significantly affects the liquid supply to the nozzle. Under extremely low surface tension (<0.033 N/m), the suspended droplet surface experiences low resistance to vertical motion within the suspension, leading to ink accumulation at the nozzle tip, causing the "climbing needle" phenomenon. Compared to traditional mechanical liquid supply methods, the pneumatic liquid supply method is more stable and can prevent the "climbing needle" phenomenon caused by capillary effects. The pneumatic liquid supply system mainly consists of an air compressor, pressure regulator, and tubing.

(3) AC Electric Field Power Supply Module

The core of EHD jet printing is the application of the electric field. The AC electric field power supply module, composed of a function generator and a high-voltage amplifier, provides the required AC electric field between the nozzle and the metal base.

(4) Observation Module

The observation module uses an industrial camera with a resolution of 2448×2048 and a frame rate of 35 FPS. It can communicate with a computer via a USB3.0 interface, and the image display software on the host computer can capture video images. A telecentric lens with a working distance of 20 cm and a field of view of 8.45×7.07 mm is selected.

(5) Motion Control Module

The motion control module mainly includes three parts. The first part is the three-dimensional displacement axis, including the X, Y, and Z directions, using the HIWIN KK series module. Since the experiment has requirements for the effective travel, precision, and movement speed of the axis, and the precision requirements for the XY axes are higher than those for the Z axis.

Development of Control Software for EHD Jet Printing Platform:

To enable coordinated control of the hardware components of the EHD jet printing system, this paper has developed the corresponding control software for EHD jet printing in the LabVIEW development environment. The control software manages the EHD printing nozzle module, flow supply module, AC electric field power supply module, observation module, and motion control module, enhancing their interconnectivity and achieving coordinated control to complete the experimental research on EHD jet printing.

Figure 2: Schematic Diagram of Communication Between Modules and Host Computer

Experimental Results:

An EHD jet printing platform for insulating substrates has been developed. In terms of hardware, an EHD jet printing platform was built. To address the issue of unstable printing due to charge accumulation on insulating substrates, an AC high-voltage amplifier and a pulse function generator were configured to provide a positive and negative AC electric field for stable printing. A real-time monitoring system for the printing process was established, capable of monitoring the jet shape during printing. In terms of software, to achieve coordinated control of the printing, motion, imaging, and other functional modules during printing, control software for the EHD jet printing platform on insulating substrates was written using LabVIEW, achieving visual operation and enhancing the overall controllability of the printing device.

High-Voltage Amplifier Recommendation: ATA-7015

Figure: Specification Parameters of the ATA-7015 High-Voltage Amplifier

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