The past 25 years have seen the rapid development of “additive manufacturing,” commonly known as three-dimensional printing (see PHYSICS TODAY, October 2011, page 25). Rather than using etching or other subtractive techniques to remove material and leave behind 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, Jürgen Stampfl and colleagues at the Vienna University of Technology have demonstrated a 3D printing technique on the 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 can trigger the polymerization of the resin, but the process requires the absorption of two photons. That...
