A decade of advances in femtosecond laser fabrication of polymers: mechanisms and applications

We overview principles and developments of three-dimensional (3D) direct laser writing in polymers. Challenges to reach efficient structuring with sub- 100 nm spatial resolution are presented. Research into the structuring by ultrashort laser pulses has seen an immense growth over the last decade due to its flexibility, easy handling and variety of applications. Here, a discussion regarding the mechanisms of the linear and nonlinear light absorption at tight focusing conditions and typical writing parameters are provided. The traditional and novel polymers together with their photosensitization and sample developing strategies are reviewed. Sub- 1 ps pulses are capable to create cross-linkable species by direct absorption and bond breaking at ∼TW/cm2 irradiance. Confined thermal and linear absorption via avalanche ionization is an efficient use of light energy for localized polymerization. This is a unique feature of ultrashort laser. Applications in microoptics, photonics, microfluidics and cell scaffolds are presented. Directions of up-scaling the fabrication throughput for industrial demands are introduced. 3D laser writing is becoming a part of wider field of additive manufacturing techniques which is innovating for creation of microdevices