Back in January of this year a research paper entitled, Toward Nanoscale Three-Dimensional Printing: Nanowalls Built of Electrospun Nanofibers was published by Drs. Minhee Lee and Ho-Young Kim of Seoul National University’s Mechanical and Aerospace Engineering Department in South Korea.
The paper didn’t seem to garner much attention from the 3D printing community at large, and in fact it took some time before I became aware of it. But after a brief examination, it became obvious that it needed more attention, so I began to dig. What I found was a story about a development that has the potential of being a game changer in the world of nano-scale additive manufacturing.
Electrospinning is a process by which fibers can be created from a liquid solution by using an electrical charge to draw very delicate micro and nanoscale fibers out of a nozzle, rather than using hydraulic, pneumatic, or mechanical pressure to push the material out in the conventional manner. Understanding this process, and its current limitations, is key to appreciating the significance of Drs. Lee and Kim’s development.
Electrospinning was first patented in 1900 and went largely unused until the early 1990s. It was, and still is, used mostly to manufacture high efficiency non-woven filters for various applications. The reason for this is that the fibers produced by the process cannot be accurately controlled during the manufacturing process. The electrical charge needed to produce the fibers also causes the individual particles that make up the fibers to repel one another. This causes them to emerge from the production nozzle in an unstable and somewhat chaotic manner. It is this lack of control that limits the process and makes it unsuitable for anything other than what it is currently used for. An analogy that helps convey understanding of the problem would be if you imagine trying to print a geometric object with a can of “Silly String”.
This is a real shame, because one of the primary advantages of the process is its ability to produce fibers that vary in their structures, which would allow them to be utilized for very specific applications. Fibers can be solid and smooth, be of varying geometry (beaded), smooth and hollow, or even porous. In addition, due to the fact that fibers produced in this way can be relatively defect free, the resulting materials produced could be far stronger than in other manufacturing processes.
This is where Dr. Lee and Dr. Kim’s development comes in. They have found a way to control and stabilize the production of the fibers, at least in a limited way. Dr. Kim explains, “We show[ed] that the electrified nanojet, which tends to become unstable when travelling in air because of coulombic repulsion, can be stably focused onto the microline of a metal electrode. On the conducting line, the polymer nanojet is spontaneously stacked successively to form a wall-like structure.”
While a simple stacked wall of nanofibers may be a far cry from being able to print out complex geometric shapes on the nano-scale, it is a great first step. Being able to utilize, what amounts to FDM 3D printing on the nano-scale, would open up entire new areas for exploration and development. But there is yet much work to be done.
“Full 3D control of an electrospun nanojet would possibly revolutionize the current nanofabrication technology, which we aim to achieve in the long run; however, we believe that such great achievement cannot be made with a single step. Further development[s] for the precise control of the nanojet could realize full 3D nanofabrication.” Dr. Kim explained. He added, “It is our eventual goal, I hope that our technology will be further sophisticated in a way that a CAD drawing can be easily converted to nanoscale three-dimensional objects.”
Whether this turns out to be a revolutionary development or merely a scientific and engineering curiosity of limited use is yet to be determined. But, as 3D printing research tends to do, it raises some tantalizing possibilities…and hopes.
