Utilizing the Sensitization Effect for Direct Laser Writing in a Novel Photoresist Based on the Chitin Monomer N-acetyl-D-glucosamine

The great flexibility of direct laser writing (DLW) arises from the possibility to fabricate precise three-dimensional structures on very small scales as well as the broad range of applicable materials. However, there is still a vast number of promising materials, which are currently inaccessible requiring the continuous development of novel photoresists. Herein, a new bio-sourced resist is reported that uses the monomeric unit of chitin, N-acetyl-D-glucosamine, paving the way from existing hydrogel resists based on animal carbohydrates to a new class of non-hydrogel ones. In addition, it is shown that the combined use of two photoinitiators is advantageous over the use of a single one. In this approach, the first photoinitiator is a good two-photon absorber at the applied wavelength, while the second photoinitiator exhibits poor two-photon absorbtion abilities, but is better suited for cross-linking of the monomer. The first photoinitiator absorbs the light acting as a sensitizer and transfers the energy to the second initiator, which subsequently forms a radical and initializes the polymerization. This sensitization effect enables a new route to utilize reactive photointiators with a small two-photon absorption cross section for DLW without changing their chemical structure.

Automated summary

The great flexibility of direct laser writing (DLW) comes from the ability to fabricate precise 3D structures in small scales and the wide range of applicable materials. This study reports a new bio-sourced resist using chitin as the monomeric unit, paving the way for non-hydrogel resists. It is also shown that using two photoinitiators is more advantageous than using a single one, where the first one acts as a sensitizer and transfers energy to the second one for initiating polymerization.