3D Ink Printing: A Hidden Side to 3D Printing

February 23rd, 2023 | 3D Printing

Olaf Schmied

When searching online about 3D printing, all sorts of articles are found about upgrades, filaments, and whether purchasing a 3D printer is right for you. Videos document all kinds of strategies for printing difficult filaments and parts while testing orientations and equipment. The vast majority of this content deals with Bowden-style, filament-extruding 3D printers, but did you know there are other uses for 3D printing? In this article, 3D ink printing will be discussed.

Ink Printing:

While many believe 3D printing took off because of filament 3D printing, another main reason has to do with the fabrication of electronics (1). As electronics have advanced, cheaper and more efficient methods of development and creation have been explored. 3D printing has played a major role in this process, not because cases or other plastic goods for electronics can be 3D printed, but rather because it's possible to 3D print the electronics themselves.

3D Printed Quantum Dot Light-Emitting Diode Image adapted from Kong, L. Y.; Tamargo, I. A.; Kim, H.; Johnson, B. N.; Gupta, M. K.; Koh, T.; Chin, H.; Steingart, D. A.; Rand, B. P.; McAlpine, M. C. 3D Printed Quantum Dot Light-Emitting Diodes. Nano Lett. 2014, 14, 7017-7023

Ink printing is an incredibly vast field of 3D printing that not a lot of people know and for good reason. Ink printing is rather complex when compared with normal 3D printers. Inks do not layer exactly like filaments, and typically, for circuits or other purposes, you do not want a large amount of material involved. Because of this, ink 3D printing involves dispensing controlled amounts of fluids upon solid curved and complex surfaces. Furthermore, different inks have different levels of viscosity that can make it difficult to control how much ink is dispensed. Viscosity deals with how easy it is for a liquid to flow. For example, water is not viscous at all and readily pours from containers like glasses and bowls. Molasses and honey, however, both have a high resistance to flow and are therefore considered viscous. Inks that have a low viscosity are harder to control in ink printing because, like water, they have a tendency to drip after they are finished dispensing.

Common Setup:

Like standard 3D printing, there is not one printer setup that works for all needs, however, in general, most ink printers work in a very similar fashion.

Ink printers involve using three different types of systems together: Printing, Pressure Regulating, and Vision (2). The Printing System is where the inks are dispensed onto an object. The Pressure Regulating System is used to controllably dispense inks and functions in two ways. First, it is used to apply pressure to ink to force it out of a syringe. This is very similar to how extruders function in standard 3D printing. The difference is, for non-viscous materials, when ink is finished, a vacuum must be applied to keep the material from dripping. For viscous materials, this is not always needed as they function much like filaments and should not drip. Finally, the Vision System is used to keep track of distance recognition and often uses a complementary metal-oxide-semiconductor (CMOS) laser sensor (2).

Systems of Common Ink Printers

There are a large variety of inks currently available depending on the application. Some examples include Graphene inks, Carbon nanotube inks, Semiconductor inks, Dielectric inks, Conductive Polymers, Metallic Organic Decomposition inks, and Metallic Nanoparticle inks (3). Literature has shown that when printed in specific layers, different electronics can be fabricated at a reasonably small scale. For instance, in a paper published in 2014 in Nano Letters, researchers were able to create light-emitting diodes using quantum dot inks (2). Light-emitting diodes (LEDs) were made by printing different layers of ink on top of one another. The first layer was printed using Silver nanoparticle ink. The second layer was made of poly(ethylenedioxythiophene): polystyrene sulfonate (PEDOT: PSS) ink. The third layer was fabricated using poly[N, N'-bis(4-butlyphenyl)-N, N'-bis(phenyl)-benzidine] ink. Next, the fourth layer was printed using Cadmium Selenide/Zinc Sulfide (CdSe/ZnS) quantum dot (QD) ink. Finally, the last layer was formed using Eutectic Gallium Indium liquid metal (EGaIN) ink. Each layer serves a specific purpose in making the LED. For example, the sintered Silver nanoparticle layer is used as the anode, and the EGaIn layer is used as the cathode. Most importantly, the quantum dot layer is used to emit light. By printing all these ink layers one on top of another, a functional electronic is made (2).

Of course, this is but one example. There are many more in the literature where all kinds of electronics ranging from radiation detectors to temperature and pressure sensors are fabricated (4, 1). All in all, 3D ink printing allows for unique and complex products to be made that would normally not be feasible.

Sources:

(1) Lu, B.; Lan, H.; Liu, H.; Additive manufacturing frontier: 3D printing electronics. Opto-Electronics Advances. 2018, 1, 170004

(2) Kong, L. Y.; Tamargo, I. A.; Kim, H.; Johnson, B. N.; Gupta, M. K.; Koh, T.; Chin, H.; Steingart, D. A.; Rand, B. P.; McAlpine, M. C. 3D Printed Quantum Dot Light-Emitting Diodes. Nano Lett. 2014, 14, 7017-7023

(3) Tan, H. W.; An, J.; Chua, C. K.; Tran, T. Metallic Nanoparticle Inks for 3D Printing of Electronics. Adv. Electron. Mater. 2019, 5, 1800831

(4) Brunbauer, F. M.; Lupberger, M.; Meuller, H.; Oliveri, E.; Pfeifler, D.; Ropelewski, L.; Scharenberg, L.; Thuiner, P.; van Stenis, M. 3D printing of gaseous radiation detectors. JINST. 2019, 14, P12005

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