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Experimental and numerical study of laser-induced secondary jetting

Abstract The generation of liquid jets and drops using tightly focused femtosecond laser pulses near a liquid–air interface is a convenient contactless solution for printing functional materials as well as bio-materials. Jets and drops emerge following the nucleation of a cavitation bubble in the liquid bulk by a laser-induced plasma. During the initial expansion of the bubble, a thin and fast jet is produced at the liquid surface. Moments later a second thick and slow jet emanates from the surface when the bubble has nearly deflated. Despite potential applications, little is known about the mechanism behind this complex phenomenology. Here, experiments and simulations are used to investigate this two-jet process. Counter-intuitively, the second jet is not the result of bubble expansion, as with the first jet, but originates from the secondary flows induced by the bubble dynamics. Our study links the second jet properties to the control parameters of the problem and establishes a phase diagram for its emergence.