The past 25 years have seen the rapid development of "additive manufacturing" commonly known as three-dimensional printing. Rather than using etching or other subtractive techniques to remove material and leave begind the desired shape, 3D printing, as its name suggests, forms shapes by adding material in designated patterns. The products, which can range in scale from airplane parts to dental implants to piezoelectric transducers, typically are fabricated one layer at a time. Now, Jan Torgersen and colleagues at the Vienna University of Technology have demonstrated a 3D printing technique on nanoscale that not only avoids that limitation but is significantly faster.
The Vienna technique relies on two-photon polymerization. Femtosecond pulses from an 800 nm laser are focused within a volume of light sensitive resin. The pulse triggers the polymerization of the resin, but the process requires the absorption of two photons. That only happens at the focal point, where the intensity is sufficiently strong. As the laser is scanned through the material, it leaves in its wake a solidified line a few hundred nanometres wide. And unlike layer-by-layer techniques, the polymerization can occur anywhere in the resin volume. Large overhangs, such as the tail of this micron-scale race car, can thus be produced without supporting material underneath. Two-photon polymerization, however, has traditionally been slow, on the order of millimetres per second: But building on earlier work from 2011 and incorporating a novel photoinitiator system and finely tuned mechanical setup, the Vienna team reached speeds up to 5 m/s. This race car, 285µm long, was fabricated in just 4 minutes (Cicha et al. J. Appl. Phys 110, 054911, 2011, Image courtesy of the Vienna University of Technology).
About Jan Torgerson:
Jan Torgersen is an Associate Professor at NTNU Trondheim. He is an expert in Nanofabrication with special focus on atomically thin film coating and high resolution additive manufacturing. He obtained his PhD from Vienna University of Technology and went to Stanford University for his post doc, where he is still appointed as guest lecturer. His research interests are biocompatible photoploymerizable hydrogels for tissue engineering as well as material property tuning with conformal surface coatings.
Kunstakademiet i Trondheim
Norwegian University of Science and Technology (NTNU)