Direct current-dielectrophoresis assisted microscale machining of metal by femtosecond pulsed laser

Abstract

Accumulation of ablation debris particles interferes with femtosecond laser micromachining of high-aspect ratio grooves in metal. Debris removal from such grooves by an air or inert gas jet requires that the gas jet axis be aligned with the groove. This requirement constrains the motion system design and programming as well as the gas nozzle design for cutting of arbitrary shapes. Gas jet debris removal is also not feasible in vacuum environments. In this study, a novel technique based on DC-dielectrophoresis (DEP) for removing debris from the cut groove was investigated. Femtosecond laser ablation of linear and circular grooves from thick sections of aluminum was performed with no debris removal and with debris removal by air jet or DC-DEP force. Ablation depth and precision were compared for the three experimental conditions. Debris removal by DC-DEP force resulted in the most accurate, consistent, and orientation-independent machining of high-aspect ratio grooves. Moreover, larger electric fields exerted stronger DC-DEP force on debris particles and resulted in better ablation precision and machining rate.