Photopolymerization
Fresnel lens.
Courtesy of Femtika.
3D gyroid structure.
Courtesy of Femtika.
Laser-induced photopolymerization, also known as direct laser lithography or direct laser writing, is a technique for forming three-dimensional (3D) micro- and nanostructures with variable architectures and subwavelength resolution.
The technique relies on multiphoton absorption in materials, such as photosensitive resin, typically transparent at the laser wavelength. Chemical changes occur at the laser focal spot via the absorption of two or more photons. The laser radiation is well-controlled for rapid prototyping of arbitrary 3D shapes with fine features. In particular, laser-induced photopolymerization is applied for the manufacturing of mesoscale optical, photonic, microfluidic components, and complex scaffolds for tissue engineering.
While laser-induced photopolymerization is mainly associated with petroleum-derived resins, the trend is shifting towards using bio-based materials obtained from renewable sources. Such an environment-friendly approach offers easy processing, fulfills technological, functional, and durability requirements, and ensures increased bio-compatibility, recycling, and eventually lower cost. Research groups from Vilnius University and Kaunas University of Technology have recently employed a bio-based resin derived from soybean oil, which can be processed even without the addition of a photoinitiator. Their results show a high potential of the bio-based resins for high fidelity prototyping and additive manufacturing. See their publication for more details.
The photopolymerization process is effectively carried out using PHAROS and CARBIDE femtosecond lasers with their fundamental wavelength (1030 nm) or higher harmonics (515 nm, 343 nm), or a wavelength-tunable industrial-grade I-OPA (320 – 10000 nm). High short- and long-term stability, along with high beam quality, ensure the robust and precise formation of 3D micro- and nanostructures.
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