Photopolymerization-based additive manufacturing offers a powerful route for rapid production of complex three-dimensional structures. However, it faces a tradeoff: single-photon absorption (1PA) enables fast polymerization and high throughput but lacks resolution, whereas two-photon absorption (2PA) delivers sub-micron precision at the cost of speed.
To address this limitation, we propose a method combining 2PP and one-photon absorption to leverage the complementary strengths of both mechanisms in Fig. 1. A continuous-wave (CW) laser at 405 nm is used to pre-sensitize the resin via 1PA, rapidly reaching the polymerization threshold, followed by 2PA using a tightly focused femtosecond (fs) laser beam at 780 nm to provide remaining energy needed to surpass threshold and solidify the resin. The material is only polymerized at the intersection volume of two light sources. This sequential excitation approach significantly affects voxel growth kinetics, lowering the energy threshold and accelerating the polymerization. We also develop a diffusion-free theoretical model that captures the underlying dynamics: oxygen depletion and sub-threshold latent polymerization induced by the 1PA pre-sensitization for more efficient 2PA. Experimental results demonstrate that pre-sensitization using a light-sheet exitation reduces the required fs laser power by 29% and a two-fold decrease in exposure time compared with polymerization driven only by 2PA. Additionally, it enhances axial voxel resolution by 63%. Our method is widely applicable in various micro- and nanomanufacturing, offering a promising path toward faster and finer high-resolution 3D microfabrication.
We are currently investigating additional techniques to further accelerate two-photon polymerization.
Publication:
B. Unlu, M.I. Álvarez-Castaño, A. Boniface, Y. Pu, C. Moser, Single-photon-assisted two-photon polymerization, Addit. Manuf. 94 (2024) 104455. https://doi.org/10.1016/j.addma.2024.104455.
Contact:
Buse Unlu, [email protected]