Microcapsule flow behaviour in porous media

Deformation and rupture of microcapsules flowing through constricted capillary

The dynamics of deformable microcapsules flowing through constricted channels is relevant in target delivery of chemicals in physiological systems, porous media, microfluidic medical diagnostic devices and many other applications. In some situations, the microcapsules need to sustain the stress they are subjected to as they flow through constricted channels and in others, the stress may be the rupture trigger used to release the internal content. We experimentally investigate the flow of monodispersed gellan gum microcapsules through a constricted capillary tube by measuring the evolution of the pressure difference and flow visualization. The maximum pressure difference and capsule deformation is obtained for capsules with different diameter and shell thickness. We map the conditions, e.g. diameter and shell thickness, at which the capsule membrane ruptures during the flow, releasing its internal phase.

Control of viscous fingering through variable injection rates and time-dependent viscosity fluids: Beyond the linear regime

During the past few years, researchers have been proposing time-dependent injection strategies for stabilizing or manipulating the development of viscous fingering instabilities in radial Hele-Shaw cells. Most of these studies investigate the displacement of Newtonian fluids and are entirely based on linear stability analyses. In this work, linear stability theory and variational calculus are used to determine closed-form expressions for the proper time-dependent injection rates Q(t) required to either minimize the interface disturbances or to control the number of emerging fingers. However, this is done by considering that the displacing fluid is non-Newtonian and has a time-varying viscosity. Moreover, a perturbative third-order mode-coupling approach is employed to examine the validity and effectiveness of the controlling protocols dictated by these Q(t) beyond the linear regime and at the onset of nonlinearities.

Formation and characterization of pH-responsive liquid core microcapsules

A protocol for making microcapsules with either organic or aqueous cores and various polymers for the shell is established. Release profiles are obtained, with the effect of complete and incomplete shell formation investigated. Triggered release due to environmental pH is evaluated as a method for release targeting. Results from microcapsules with poly(4-vinylpyridine) shells showed a release of methylene blue dye when the pH was below 3.5, due to swelling of the polymer. This behavior was also observed for poly(lactide-co-glycolide) microcapsules due to cleavage of ester bonds. Both polymers showed complete release after 6 h. Various active ingredients such as polyacrylamide and hydroxypropylcellulose are also encapsulated using the established protocol.