Cavity dynamics after the injection of a microfluidic jet onto capillary bridges

The impact of solid and liquid objects onto liquids and soft solids results on the creation and expansion of an air cavity inside the impacted objects. In this paper we study the impact of microfluidic jets generated by thermocavitation processes on a capillary bridge between two parallel planar walls. Different capillary bridge types were studied, Newtonian liquids, viscoelastic liquids and agarose gels. We model the critical impact velocity for a jet to traverse a capillary bridge type. We show different types of cavity collapse, depending on the Weber number and the capillary bridge properties. We conclude that the type of collapse determines the number and size of entrained bubbles. Furthermore, we study the effects of wettability on the adhesion forces and contact line dissipation, upon cavity collapse. for hydrophobic walls a Worthington jet is energetically favourable. In contrast, for hydrophilic walls, the contact line dissipation suppresses the Worthington jet formation. Our results provide strategies for preventing bubble entrapment and give an estimation of the cavity dynamics for needle-free injection applications among other applications.