Issue 2, 2023

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


The ballistics of solid and liquid objects (projectiles) impacting on liquids and soft solids (targets) generally results in the creation and expansion of an air cavity inside the impacted object. The dynamics of cavity expansion and collapse depends on the projectile inertia as well as on the target properties. 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. Thus, we compare the cavity formation and collapse between a wide range of material properties. Moreover, we model the critical impact velocity of a jet traversing a capillary bridge type. For agarose gels with a storage modulus of 176 Pa, the critical velocity is well predicted by the model used for liquids. However, the predicted critical velocity for liquids deviates for agarose gels with a storage modulus of 536 Pa and 3961 Pa. Additionally, 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. We also conclude that upon cavity collapse, for hydrophobic walls a Worthington jet is energetically favourable. In contrast, for hydrophilic walls, the contact line dissipation is in the same order of magnitude of the energy of the impacted jet, suppressing the Worthington jet formation. Our results provide strategies for preventing bubble entrapment and give an estimation of the cavity dynamics, of relevance for, among others, needle-free injection applications.

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

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Article information

Article type
23 Sep 2022
30 Nov 2022
First published
01 Dec 2022
This article is Open Access
Creative Commons BY license

Soft Matter, 2023,19, 245-257

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

M. A. Quetzeri-Santiago and D. Fernandez Rivas, Soft Matter, 2023, 19, 245 DOI: 10.1039/D2SM01285E

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