High-resolution Patterning Using Two Modes of Electrohydrodynamic Jet: Drop on Demand and Near-field Electrospinning

Summary

Here, we present a protocol to produce high-resolution conductive patterns using electrohydrodynamic (EHD) jet printing. The protocol includes two modes of EHD jet printing: the continuous near-field electrospinning (NFES) and the dot-based drop-on-demand (DOD) EHD printing.

Abstract

Electrohydrodynamic (EHD) jet printing has drawn attention in various fields because it can be used as a high-resolution and low-cost direct patterning tool. EHD printing uses a fluidic supplier to maintain the extruded meniscus by pushing the ink out of the nozzle tip. The electric field is then used to pull the meniscus down to the substrate to produce high-resolution patterns. Two modes of EHD printing have been used for fine patterning: continuous near-field electrospinning (NFES) and dot-based drop-on-demand (DOD) EHD printing. According to the printing modes, the requirements for the printing equipment and ink viscosity will differ. Even though two different modes can be implemented with a single EHD printer, the realization methods significantly differ in terms of ink, fluidic system, and driving voltage. Consequently, without a proper understanding of the jetting requirements and limitations, it is difficult to obtain the desired results. The purpose of this paper is to present a guideline so that inexperienced researchers can reduce the trial and error efforts to use the EHD jet for their specific research and development purposes. To demonstrate the fine-patterning implementation, we use Ag nanoparticle ink for the conductive patterning in the protocol. In addition, we also present the generalized printing guidelines that can be used for other types of ink for various fine-patterning applications.

Introduction

EHD jet printing has been widely used in various areas, such as printed electronics, biotechnology, and advanced material applications, because it is capable of high-resolution and low-cost direct patterning¹. The printed line width or printed dot size could be reduced to 1 µm, which is significantly smaller than that of conventional piezo-based inkjet printing¹.

In EHD printing, a small portion of ink (or meniscus) is pushed out of the nozzle tip and maintained by controlling the flow rate^1,2,3,....

Protocol

For health and safety purposes, prior to using any ink and cleaning solution, refer to the material safety datasheet (MSDS).

1. Drop-on-demand Electrohydrodynamic Jet Printing Using Silver Nanoparticle Ink

1. Fill the filtered silver nanoparticle (AgNP) ink in the ink reservoir of the EHD printing system.
   Note: Commercially available AgNP ink can be used for the inkjet purpose. The ink should have a viscosity of around 10 cP and a surface tension of 20 ~ 40 mN/m to obtain drop-on-demand jetting.
2. Make a nozzle for the DOD EHD printing by using a thermal puller.
   1. Place a glass capillary [inner diameter (ID) ....

Results

Dot-based drop-on-demand printing:
DOD printing is based on one droplet jetting per one jetting trigger. To produce DOD jetting, low-viscous ink with a viscosity of approximately 10 cP should be used. The ink requirement for EHD DOD printing is similar to that of the conventional DOD inkjet, as is the EHD printing method to that of the conventional DOD inkjet. In the case of conventional inkjet printing, the raster printing technique has been widely used, because it i.......

Discussion

In this protocol, we focus on printing fine patterns using AgNP ink with two modes: DOD EHD printing and NFES. However, the EHD jet printing application is not limited to the conductive ink using AgNP. Here, we will discuss the general guidelines for the selection of ink, the system configuration, and other printing parameters needed to use EHD jet printing for various fine-pattern applications.

The first and most important step for EHD printing is ink selection and preparation. The ink used i.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
EHD integrated printing system	Psolution Ltd., South Korea	PS300
Harima Ag Nanoparticle ink	Harima Inc., Japan	Harima NPS-JL	Ag solid content: ~ 53 wt%, Viscosity: ~10 cP, Surface tension: ~30 mN/m
Glass capillary	Narishige Scientific Instrument Lab	G-1	Inner diameter: 1 mm; Used to make nozzle for DOD EHD jet printing using thermal puller
Nozzle thermal puller	Sutter Instrument, USA	Sutter P-1000
Microscope Slides (Glass subtrate)	Paul-Marienfeld & Co.KG, Germany	10 006 12	Dimension (L x W x T): 76 mm x 26 mm x 1 mm
Magnetic Stirrer	Barnstead Thermolyne Corp., USA	Cimarec SP131635
Vortex Stirrer	Jeiotech, South Korea	Lab Companion VM-96T
Ag nanopaste	NPK, South Korea	ES-R001	Ag solid content: ~85.5 wt%, Viscosity: ~11000 cP
Poly ethylene oxide (PEO)	Sigma-Aldrich, USA	372773-500G	Mw = 400000
Ethanol	Sigma-Aldrich, USA	459836-500ML