Multiphoton Polymerization Using Femtosecond Bessel Beam for Layerless Three-Dimensional Printing

Photopolymerization enables the printing of three-dimensional (3D) objects through successively solidifying liquid photopolymer on two-dimensional (2D) planes. However, such layer-by-layer process significantly limits printing speed, because a large number of layers need to be processed in sequence. In this paper, we propose a novel 3D printing method based on multiphoton polymerization using femtosecond Bessel beam. This method eliminates the need for layer-by-layer processing, and therefore dramatically increases printing speed for structures with high aspect ratios, such as wires and tubes. By using unmodulated Bessel beam, a stationary laser exposure creates a wire with average diameter of 100 μm and length exceeding 10 mm, resulting in an aspect ratio > 100:1. Scanning this beam on the lateral plane fabricates a hollow tube within a few seconds, more than ten times faster than using the layer-by-layer method. Next, we modulate the Bessel beam with a spatial light modulator (SLM) and generate multiple beam segments along the laser propagation direction. Experimentally observed beam pattern agrees with optics diffraction calculation. This 3D printing method can be further explored for fabricating complex structures and has the potential to dramatically increase 3D printing speed while maintaining high resolution.