Two-Photon Polymerization (2PP) is suited for the fabrication of nearly any 3D micro- and macrostructures and structured surfaces. It uses tightly focused femtosecond laser pulses to confine the polymerization of a photopolymer to the focal volume.
The underlying process – Two-Photon Absorption (TPA) – can only occur if the light intensity is sufficiently high so that the solidification of the material is located in the tiny focal volume. For 3D fabrication, the focal volume is scanned in 3D space followed by a solvent wash to separate the remaining liquid photo-polymer from the solidified 3D structure. Thus 2PP offers potential for innovative and very sophisticated microstructures and, compared to conventional methods, is an easy, fast, low cost and environmentally friendly procedure.
In the project FOWINA Fraunhofer ISC and Fraunhofer IIS currently develop complex angular filter structures to realize color sensors directly on chip level. The sensors measure optical spectra independently of the incidence of the light and can be employed in smartphones or LED lighting in cars.
In a second project – µFLO – Fraunhofer ISC and Fraunhofer ILT are working on freeform 3D microlenses and microfluidic components for optical or medical devices.
For both projects FOWINA and µFLO the Fraunhofer institutes use inorganic-organic hybrid polymers (ORMOCERs) developed by Fraunhofer ISC. Apart from Two-Photon Polymerization, ORMOCERs can be processed with conventional UV lithography, Nanoimprint Lithography (NIL) and other printing and replication techniques.