Two-Photon Absorption Produces Sculpture, Spring

Researchers at Osaka University in Japan have used two-photon polymerization to construct a sculpture of a bull the size of a red blood cell and a 300-nm-diameter spring. The work, which they described in the Aug. 16 issue of Nature, demonstrates that the laser technique offers a subdiffraction-limit spatial resolution of 120 nm for building microstructures.

The researchers employed a Ti:sapphire laser tuned to 780 nm and producing 150-fs pulses at 76 MHz to fabricate the pieces by two-photon absorption in a resin. The laser's pulse energy was 137 pJ. Commercially available urethane acrylate and photo-initiators served as the medium.