Opto-hydrodynamic processing of materials using microdroplets

Abstract

A novel surface processing technique entitled “Droplet Opto-hydrodynamic Processing” (DOP) is introduced. The process is based on the laser-induced breakdown (LIB) of a micro liquid droplet and subsequent ejection of a high-speed micro liquid jet. The speed of the microjet (∼1600 m/s) is high enough to ablate a variety of materials with substantially large removal rates and remove nanoscale particles from solid surfaces. In particular, the combined effect of the hydrodynamic impact of the jet and the partially transmitted (refocused) laser pulse can form microstructures with negligible thermal effects. Furthermore, the small volume of the liquid droplet (∼10 nanoliter per pulse) enables precise and selective processing of surfaces. In this work, the hydrodynamics of the micro liquid jet induced by LIB of a free-falling droplet is analyzed using a Q-switched Nd:YAG laser. The results of DOP of metals are presented with discussions on the material removal mechanisms. It is demonstrated that the laser-generated liquid jet can remove particles as small as 10 nm from Si wafers.A novel surface processing technique entitled “Droplet Opto-hydrodynamic Processing” (DOP) is introduced. The process is based on the laser-induced breakdown (LIB) of a micro liquid droplet and subsequent ejection of a high-speed micro liquid jet. The speed of the microjet (∼1600 m/s) is high enough to ablate a variety of materials with substantially large removal rates and remove nanoscale particles from solid surfaces. In particular, the combined effect of the hydrodynamic impact of the jet and the partially transmitted (refocused) laser pulse can form microstructures with negligible thermal effects. Furthermore, the small volume of the liquid droplet (∼10 nanoliter per pulse) enables precise and selective processing of surfaces. In this work, the hydrodynamics of the micro liquid jet induced by LIB of a free-falling droplet is analyzed using a Q-switched Nd:YAG laser. The results of DOP of metals are presented with discussions on the material removal mechanisms. It is demonstrated that the laser-genera...