Microfluidic probing of the complex interfacial rheology of multilayer capsules

Abstract

Encapsulation of chemicals using polymer membranes enables to control their transport and delivery for applications such as agrochemistry or detergency. To rationalize the design of polymer capsules, it is necessary to understand how the membranes' mechanical properties control the transport and release of the cargo. In this article, we use microfluidics to produce model polymer capsules and study in situ their behavior in controlled elongational flows. Our model capsules are obtained by assembling polymer mono and hydrogen-bonded bilayers at the surface of an oil droplet in water. We also use microfluidics to probe in situ the mechanical properties of the membranes in a controlled elongational flow generated by introducing the capsules through a constriction and then in a larger chamber. The deformation and relaxation of the capsules depend on their composition and especially on the molecular interactions between the polymer chains that form the membranes and the anchoring energy of the first layer. We develop a model and perform numerical simulations to extract the main interfacial properties of the capsules from the measurement of their deformations in the microchannels.

Axisymmetric Stokes flow due to a point-force singularity acting between two coaxially positioned rigid no-slip disks

“…In many biologically and industrially relevant applications, finite-size effects become crucial for an accurate and reliable description of transport processes ranging from the microscale to the nanoscale. Prime examples include the ionic transport and electrokinetics in small-scale capacitors (Marini Bettolo (Daiguji et al 2004), and the rheology of droplets, capsules or cells in constricted/structured microchannels (Park & Dimitrakopoulos 2013;Le Goff et al 2017;Trégouët et al 2018Trégouët et al , 2019, where boundary effects may play a pivotal role.…”

Droplet Microfluidics for Food and Nutrition Applications

“…For protein-stabilized emulsions, it is generally assumed that the formation of the interfacial layer structure takes place in time ranges between minutes and days. In previous studies, authors investigated interfacial rheology using microfluidics at time intervals up to hours, and found considerable differences in interfacial rheology [ 86 , 87 , 88 ]. However, a very recent study showed that the onset of these processes can already be detected at sub-second time scales [ 89 ].…”

Current Advances of Hollow Capsules as Controlled Drug Delivery Systems

“…Furthermore, LbL-assembly method can only be utilized on water-soluble and charged polymer (polyelectrolyte) components, [40,41] and polymeric materials can be lost after each washing step, leading to uneven distribution between different layers. To address these issues, many modified techniques have been introduced, for instance, spin assembly, [42] spray assembly, [43,44] and fluidic assembly, [45,46] have been employed to speed up the coating procedure. To expand the types of compounds that could be used as LbL building blocks, an improved method that involves two steps of the assembly procedure was proposed.…”