What is Two-Photon Polymerization?

Nano- and microscale 3D printing offers design freedom and efficiency, paving the way for numerous pioneering innovations, particularly in the fields of micro-optics and micromechanics. In turn, these achievements drive new developments, promoting technological progress. As a result, the commercialization of 3D printing techniques that can be used to produce these micro- and nano-objects has increased in recent years. One of the most important processes in this context is two-photon polymerization.

Two-photon polymerization is often abbreviated simply as 2PP. Other terms that can be found concerning this technology are two-photon lithography, direct laser writing, or two-photon polymerization graphene. 2PP falls under the umbrella microscale 3D printing and could be considered an advanced additive manufacturing technology. The basic principles were developed by Shoju Maruo, Osamu Nakamura and Satoshi Kawata at Osaka University in 1997. Since then, numerous companies have continued developing the technology, bringing their equipment to market under various patented names.

A 3D printed microstructure: two-photon polymerization can be used to produce complex structures at the micro- and nanometer scale (photo credits: Fraunhofer ISC)

How Does Two-Photon Polymerization Work?

Two-photon polymerization, as the name suggests, is based on the principle of photopolymerization. Here, targeted exposure to light triggers the polymerization, or the process to bring monomers together to create a polymer chain, of synthetic resins. This chain reaction causes the molecules to bond and harden, resulting in 3D models. All light-curing processes work in similar ways, but differ in the procedure.