Efficient Photoinitiators for Two-Photon Polymerization

Abstract

Two-photon polymerization (2PP) is a versatile laser fabrication technique that allows the creation of 3D structures at micro- and nanometer precision. The structures are created additively in direct accordance to a computer-aided design. It requires tightly focused fs-pulsed light sources usually operating in the near infrared wavelength range. Despite its versatility and 3D capabilities, the low process speeds achievable has prevented the technology from its broader use in various applications. Optimizing the photopolymerizable formulations is key for increasing the writing speed and the process window making 2PP more economic and easy to use. This chapter gives an insight into optimizing photoinitiators for absorption of two photons and radical formation for subsequent photopolymerization. In particular, one compound is presented that can facilitate writing speeds above 150 mm s−1 and laser powers as low as 110 mW. Remarkably, this compound has a lower two-photon activity than its counterpart with different central acceptors. This indicates that various properties other that the two-photon absorption cross section have to be addressed for facilitating efficient initiation in two-photon photopolymerization.

Biodegradable Tyramine Functional Gelatin/6 Arms-PLA Inks Compatible with 3D Two Photon-Polymerization Printing and Meniscus Tissue Regeneration

“…The addition of scavenger molecules or the change of solvent could help improve resolution. 57 Even though structure resolution and ink formulation can be improved, this is a promising result for further studies, as microstructures with such a tunable, biocompatible, degradable polymeric ink can be formed.…”

“…Moreover, the addition of Tyr-Gelatin inside the ink brought many tyramine functionalities which may contribute to greater reactivity but also to less controlled photo-cross-linking reactions due to the generation of more free radicals. The addition of scavenger molecules or the change of solvent could help improve resolution . Even though structure resolution and ink formulation can be improved, this is a promising result for further studies, as microstructures with such a tunable, biocompatible, degradable polymeric ink can be formed.…”

Micro-structured polymer scaffolds fabricated by direct laser writing for tissue engineering

“…Having the sufficient light density for the irreversible photomodification one can think of artificial scaffold creation during in vitro tests 64 and, due to already achieved high fabrication throughput, even during in vivo surgery. 65 This would enable dynamic experiments of cell proliferation or creation of custom shaped artificial scaffolds in real time.…”