17 Jun 2002
Laser photopolymerization reveals potential for making microdevices for sensors and drug delivery.
Scientists from the University of Osaka have created three-dimensional micron-sized bulls and springs by developing a high-resolution profiling technique called two-photon micropolymerization, (Nature 412 697-698).
Photopolymerization involves shining light at molecules to make them react and form a polymer. By directing two infrared lasers at a resin, Hong-Bo Sun and colleagues did just this but discovered that the resin only polymerized at the laser focal point. With this in mind, they used the laser focus to outline the desired shape of the microdevice. Sun says that by refining this technique the researchers beat the resin's diffraction limit and sculpted microdevices at a resolution of 120 nm.
"We chose the shape of a bull to demonstrate our technology as it has a sophisticated shape with sharp tips and a partially rough body," said Sun. "At only 10 by 7 microns, the model bulls are the size of red blood cells. This makes them the smallest model animals ever made artificially."
The scientists also fabricated a spring, which they oscillated by first anchoring one end to a glass substrate and adding a bead to the other. They set the spring in motion by capturing and pulling the bead with a laser-trapping force. "This must be the smallest functional micromechanical system ever produced," said Sun.
Confident that their technique is the only way to fabricate three-dimensional microdevices, the scientists are now eager to find practical applications.
"[By reaching sub-diffraction limits] we have shifted the working wavelength of photonic and optoelectronics devices into the visible and near-infrared regions," said Sun. "Two-photon polymerization will find uses in nanophotonics, MEMs and biological applications."
"[We hope to] fabricate 3D photonic crystals, complex machines for drug delivery or surgery and also micro and nano-sensors," he added.