Maskless direct micro-structuring of PDMS by femtosecond laser localized rapid curing

Polydimethylsiloxane (PDMS) is widely used to build biomedical microdevices because of its excellent properties. Prototyping 2D and 3D PDMS microdevices normally requires a long curing time and must go through multiple steps. In this paper, we propose femtosecond laser stereolithography for the rapid prototyping of PDMS 2D and 3D microstructures. This work presents a new way of rapid curing of PDMS resin on a microsecond timescale using femtosecond laser pulses of megahertz pulse frequency. The proposed technique permits single-step curing and is capable of fabricating 2D and 3D structures in micro-scale. The rapid localized curing can be explained by the volume-constrained quick temperature rise due to the accumulated heating at repetitive irradiation. The rapid cooling following the curing limits the decomposition and, therefore, the PDMS retains its mechanical strength.