Application Cases

Experiment Name: Alternating-Current-Field-Driven Single-Jet Printing Experiment

Research Direction:
Investigate the ejection and deposition behavior of electrohydrodynamic (EHD) direct-writing under an alternating-current (AC) electric field, enabling stable jetting of the EHD direct-write filament onto insulating substrates and the controllable deposition of ordered micro/nano structures.

Objectives:
The rheological properties of viscoelastic fluids and the motion/deposition of jets in DC electric fields are well documented, yet jetting of polymer solutions under AC fields remains largely unexplored.  Unlike DC fields, an AC field allows the frequency and duty cycle to be tuned so as to tailor the ejection regime.  By mastering these ejection rules we aim to establish AC-field-driven EHD direct-writing, and to quantify how solution properties, voltage waveform, and electrode gap influence droplet printing or the uniformity of EHD-written traces.

Apparatus:
Function generator, high-voltage amplifier, oscilloscope, motorized XYZ stage, syringe pump, collector substrate, high-speed camera, CCD, optical microscope.

Experimental Procedure:
The jet is imaged in real time with a high-speed camera or CCD; deposited droplet diameters are measured with an optical microscope.  A schematic of the complete system is given in Fig. 3-1.

AC-Field-Driven Single-Jet Printing Setup
The setup comprises an AC high-voltage supply, XYZ motion stage, syringe pump, collector substrate, and camera.  The positive terminal of the AC high-voltage source is connected to the metallic needle; the negative terminal is grounded to the collector plate, which is fixed on the motion stage.  The syringe pump delivers polymer solution continuously, forming a pendant droplet at the needle tip.  When the applied AC field exceeds the critical value, the droplet ejects charged droplets or a single continuous jet that is collected on the substrate for subsequent analysis.  The high-speed 3-D motion stage is shown in Fig. 3-2.

Key Hardware:
Function generator, high-voltage amplifier (ATA-7100), oscilloscope, syringe pump, high-speed camera.

Results:
Under the AC field the single jet deposits on the collector either as discrete droplets or as continuous lines, depending on polymer concentration and operating conditions.  In the electric field, surface charge accumulates on the pendant droplet, creating a normal Maxwell stress.  Once the applied voltage surpasses the onset value, the droplet ejects either charged micro-droplets (electrospray) or a single polymer jet (electrospinning); see Fig. 3-5.

Recommended High-Voltage Amplifier:

Figure: ATA-7100 High-Voltage Amplifier Specifications

Xi’an Aigtek Electronics is a high-tech enterprise specialized in the R&D, manufacture and sales of power amplifiers, high-voltage amplifiers, power signal sources, pre-amplifiers, precision voltage/current sources and other electronic test instruments.  Aigtek offers competitive test solutions and maintains one of the broadest product portfolios in the industry; demo units are available for free trial.