Fabrication of three-dimensional microstructures in positive photoresist through two-photon direct laser writing.

Three-dimensional (3D) microstructures with micron scale are fabricated in photoresist using two-photon direct laser writing with an infrared femtosecond laser at 800 nm. The positive photoresist of Novolak/diazonaphthoquinone (DNQ) is used for the fabrication of line structures and 3D microstructures. Linewidths of line structures are fabricated with laser power ranging from 1 to 15 mW and scanning speeds ranging from 5 to 50 μm s. The obtained linewidth is analyzed using an exposure kinetics model of DNQ for two-photon absorption. Both 3D inversed woodpile structures and helical structures are fabricated. Graphical abstract: Two-photon direct laser writing is used to fabricate microstructures in positive photoresist. Microstructures with helical and inversed woodpile shapes were fabricated with positive photoresist Novolak/DNQ using two-photon direct laser writing. [ABSTRACT FROM AUTHOR]