Peek behind the paper: matching speed with precision for 3D printing
In this exclusive interview with Vincent Hahn (Karlsruhe Institute of Technology), 3DMedNet takes a closer look at a new 3D printing system, capable of printing precise centimetre-sized objects with extreme detail on a submicrometric scale.
I am Vincent Hahn, PhD student in Martin Wegener’s research group at the Karlsruhe Institute of Technology (KIT) in Germany. We have built a 3D printer that builds periodic structures faster than any printer before. Prior to my PhD, I worked for Trumpf Photonics Inc (NJ, USA), after having finished my Master’s degree in Physics, also at the KIT.
Could you please tell us about the project covered in the recent 3DMedNet news piece, as well as any other related projects you may currently be working on?
Our recently published work on fast multi-focus multi-photon printing was motivated by the demand for larger, so-called, 'metamaterials'. A metamaterial is an artificially engineered material, designed and tailored to feature properties that cannot be found in nature. You can find a few examples on metamaterials, here [1–4]. Typically, such a material is comprised of unit cells arranged in a periodic lattice. Some phenomena of such materials can only be observed in large-scale materials, that means for many unit cells. 3D printing is the method of choice to build a metamaterial. However, fabricating really large samples is a tedious task, since the speed of common 3D printers is limited.
Fortunately, we were able to take advantage of their periodic structure and speed up the printing process considerably.
How do you envision your work translating into the medical field?
It is not only in metamaterials where you can take advantage of our printer’s enhanced speed. There are many groups doing cell research using 3D-printed micro-scaffolds .
Our 3D printer is not only fast, but also able to print features smaller than 1µm.
Therefore, it can and will be used to print micro-scaffolds for single cell research.
What challenges have you faced with developing your 3D printing technique?
In our printer, we split a laser beam into an array of three by three laser beams. It is important that each beam is of equal intensity when it is scanned through the liquid photoresin – that was trickier than initially expected.
What’s next for you and your research?
As of now, our printer is well suited when printing periodic structures. We would also like to print non-periodic structures while retaining the current precision and speed. There have been a few attempts by other groups previously, but they typically made trade-offs at the achievable minimum feature size.
Where do you see medical 3D printing in 5–10 years time? How could research such as yours affect this?
We have seen all sorts of 3D-printed implants already, be it a hip, a jaw, clavicles or a jack. With the minimum feature size of the 3D printing method at hand, even finer implants can be envisaged. What I am curious to see is native tissue that has been artificially grown in 3D-printed templates and is then grafted. The challenge with this is mostly on the material side: the right type of cell should feel comfortable at its proper location. In that context, functional and biodegradable polymers do play an important role.
In addition, in order to fabricate fitting templates, it will be of prime importance to come up with precise 3D models to be printed. Very accurate deep-tissue imaging modalities are required for this.
 Kadic M, Frenzel T, Wegener M. When size matters. Nat. Phys. 14, 8–9, (2018).
 Qu J, Kadic M, Naber A, Wegener M. Micro-structured two-component 3D metamaterials with negative thermal-expansion coefficient from positive constituents. Sci. Rep. 7 40643, (2017).
 Frenzel T, Kadic M, Wegener M, Three-dimensional mechanical metamaterials with a twist. Science. 358(6366), 1072–1074, (2017).
 Gansel JK, Thiel M, Rill MS et al. Gold helix photonic metamaterial as broadband circular polarizer. Science. 325(5947), 1513–1515, (2009).
 Hippler M, Lemma ED, Bertels S, Blasco E, Barner‐Kowollik C, Wegener M, Bastmeyer M. 3D scaffolds to study basic cell biology. Adv. Mater. 31(26), 1808110 (2019).