Two-Photon Polymerization:
Additive manufacturing on the micron scale

Two-Photon Polymerization can be regarded as equivalent for 3D printing on the micron scale. In contrast to UV lithography and 3D printing via stereolithography, 2PP does not treat the resin with UV light but with femtosecond laserpulses in the visible to near-infrared spectral region.  

Under normal circumstances those wavelengths would not be absorbed by the transparent resin at all. However, tight focusing and the pulsed nature of the irradiation (energy delivery in few 100s of femtoseconds) leads to two-photon absorption inside the focal volume, that triggers the same chemical transitions as in UV light illumination. Hence, the curing, i.e. solidification of the polymer is strongly confined to the tiny focal volume. It can be regarded as a three dimensional pen for true 3D microfabrication.

During 2PP processing the focal volume is scanned in all three spatial directions to create the desired structure directly from CAD data. After exposure, a solvent wash is carried out to get rid of the unexposed (still liquid) resin.

2PP scheme CeSMA
© Fraunhofer ISC
Difference of conventional one-photon polymerization (1PP) and 2PP: In 1PP the entire path of light inside the material is cured, whereas in 2PP the solidification is confined to the focal volume.
2PP Knot-like structure CeSMA
© Fraunhofer ISC
Knot-like structure fabricated with 2PP. Typical example of a design that is impossible to create with any other technology.
2PP Gyroid CeSMA
© Fraunhofer ISC
„Gyroid“ structure which demonstrates 2PP in a composite material out of hybrid polymer and nanoparticles.
2PP Unlimited height CeSMA
© Fraunhofer ISC
„Unlimited“ height of 3D structures created by 2PP. Sophisticated exposure strategies enable the fabrication of structures with dimensions only limited by the physical travel of the positioning system but not by the employed optics. In the example, the Statue of Liberty has a height of 750 µm.
2PP Different microoptics CeSMA
© Fraunhofer ISC
Demonstration of different microoptical elements on the same substrate.
2PP Microoptics CeSMA
© Fraunhofer ISC
Microvessels fabricated by 2PP in biocompatible ORMOCER®.
3D microstructure
© Fraunhofer ISC
Organic-free 3D µ-structure generated by 2-Photon-Polymerization.
Hydrogel cell scaffold structure
© Fraunhofer ISC
Hydrogel cell scaffold made of loosely intertwinded Rings with a diameter of 20 µm.
3D structuring of a composite
© Fraunhofer ISC
3D structuring of a composite consisting of a hybrid polymer and silica nanoparticles (top: 52 nm, bottom: 420 nm), which allows tailoring the surface roughness, as well as other material characteristics to be generated.

HiPS derived cardiomyocite cells

Cultured on top of a 2PP structured hydrogel scaffold

Advantages of 2PP

  • True 3D microfabrication
  • No design constraints
  • Almost any kind of substrate possible
    (even with existing topology)
  • Scalable from small voxel sizes (down to 100 nm) to cm-scale objects
  • Several fabrication strategies to increase throughput

Our competences

  • Unique combination of process technology and development of tailored hybrid polymers (ORMOCER®)
  • CAD/CAM chain: From design to prototype
  • Two devices with different wavelengths available (515 / 1030 nm; 680 - 1080 nm)
  • Substrates up to 30 x 30 cm²
  • Hardware for high-throughput manufacturing (high-precision air bairing stages + galvoscanner technology)
  • Automated procedures for parameter optimization and the manufacturing of largescale parts