Delivery of viscous drops and jets to eyeball replicas.

Front-of-the-eye (FOTE) droplet-based drug delivery presents a challenging fluid dynamics phenomenon, where many patients either miss their target or blink prematurely, leading to significant drug wastage and poor bioavailability. In this study, we investigate the influence of fluid properties and impact speed on the impact-spreading process on eyeball replica substrates in the context of both drops and jets to identify optimal parameters for maximum spreading, which has implications for bioavailability. Additionally, we investigate the role of the micro-scale protective tear film by coating the substrates with artificial tears. Our findings reveal that the presence of a tear film enhances the spreading of eye drops, and the spreading dynamics of various Newtonian and non-Newtonian fluids on both dry and wet substrates can be described by a universal scaling law.