In recent years, two-photon polymerization (2PP) has emerged as a promising technology to structure customized biomaterials in regenerative medicine. Based on nonlinear absorption phenomena, 2PP allows rapid and flexible fabrication of fully three dimensional (3D) objects with sub-100-nm resolution.
The ever-growing need for biocompatible photoinitiators (PI) necessitates knowledge of the spectral two-photon absorption (2PA) characteristics. Matching the laser wavelength to the peak of the 2PA spectrum of a particular compound can result in a significant increase of the PI’s performance. With the advent of tunable femtosecond laser systems the application window of 2PP has vastly expanded due to the broad spectral range available for structuring.
To reveal the potential of a certain PI design the z-scan technique has become a standard method to measure the non-linear properties. We have developed a completely automated z-scan setup, which requires negligible user input for the characterization. It is based on the same system used for 2PP, which allows direct comparison of the PI absorption and the polymerisation performance.
To ensure reproducibility and accuracy of measurements, our group developed an automated algorithm, which collects the required laser parameters before the scanning process. These are stored in a comprehensive library for every single measurement. Therefore, even large amounts of data are easily handled and correctly evaluated without the need to manually check each measurement.
Our setup allowed us to reliably determine the absorption properties of newly synthesized PIs and adjust the structuring wavelength. The change in wavelength resulted in significant improvement of the structuring process.
Wolfgang Steiger, Peter Gruber, Maximilian Tromayer, Agnes Dobos, Markus Lunzer, Robert Liska, and Aleksandr Ovsianikov, "Fully automated z-scan setup based on a tunable fs-oscillator (Conference Presentation)," Proc. SPIE 10492, Optical Interactions with Tissue and Cells XXIX, 1049203 (Presented at SPIE BiOS: January 29, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2289005.5751456503001.
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