Hybrid analytical/numerical modeling of nanosecond laser-induced micro-jets generated by liquid confining devices

Abstract

The generation of micro-jets with pulsed laser irradiation is a key enabling technique for microfluidic devices, printers and needle-free drug injectors. Modeling approaches for such devices are essential to optimize their design and performance. Here we present a hybrid analytical/numerical model to simulate nanosecond laser-induced micro-jets generated by a dual-chamber liquid confining device. The simulated device consists of two chambers; the first one is closed and filled with a propellant liquid and the second is filled with the liquid to be ejected and equipped with a nozzle. Laser-induced cavitation is generated in the first chamber, which is separated by an elastic membrane from the second one, to reduce the thermo-mechanical impact of the absorbed laser energy on the liquid to be ejected. By modifying the generalized form of the Rayleigh–Plesset equation to account for the pressure variation inside the chamber, we show that the geometry of the liquid confining device affects drastically laser-induced bubble dynamics and the resulting jet ejection dynamics. We also demonstrate the effect of the membrane size, laser energy and nozzle size variation on the micro-jet dynamics. We found that such devices can generate micro-jets (velocity: 0.93 m/s to 48.39 m/s) suitable for micro-drop printing (volume: 0.097 nL to 7.68 nL). Although we focused on printing applications, the modeling approach presented here can be widely adapted for designing and optimizing needle-free drug injectors and microfluidic devices.