Feasibility of laser induced jets in needle free jet injections

This paper reports a detailed characterization of laser-induced micro-jets, including ex vivo experiments using skin as a target substrate to check the feasibility in terms of needle-free jet injection. The actuation technique comprised a Nd-YAG based laser system to superheat the liquid locally, which creates a pressure wave actuating the motion of the liquid as a jet. Typical jet speeds were ~ O(10²) m/s and diameters ~ O(10¹–10²) μm and Re ~ O(10²–10⁴). We studied the effect of various system parameters related to both geometry (e.g., capillary diameter, laser focal point) and fluid properties (e.g., viscosity). To advance the understanding of liquid delivery into tissue, transient penetration dynamics and dispersion patterns were studied. Stand-off distance, mechanical strength of the proxy gel, and laser pulse energy were also found to affect the penetration of liquid jets into the skin models.