Droplet-Microfluidic Generation of Tailored Polymeric Micro-sized Capsules

A novel methodology is developed to generate hollow and porous microparticles of homogeneous size and properties

Dr. Tianjin Yang from the deMello group and co-workers have demonstrated a novel methodology that combines droplet-based microfluidics with a gelation process to generate porous polymeric capsules with high control over the size and morphology.

Porous microparticles and capsules are of significant interest for a variety of applications in material and pharmaceutical sciences. Major characteristics of such materials are the porosity, size, shape, and composition, as these will influence properties such as loading capacity and release rate. A key type of porous particles is the colloidosome, a micro-sized capsule whose shell is composed of colloidal polymer nanoparticles (NPs). Colloidosomes can serve as excellent templates for the fabrication of porous microparticles, after a solidification step to create a robust shell. However, this crucial hardening stage traditionally requires complex protocols with a difficulty to identify compatible chemicals, or that rely on high temperatures. A possible alternative is reactive gelation, which is a robust method to produce porous polymer networks that does not suffer the limitation of these conventional methods.

In this work, Dr. Tianjin Yang combines droplet-based microfluidics technology with reactive gelation to generate monodisperse, porous, hollow microparticles. A key asset of this method lies in the ability to control the shell porosity and thickness. Typically, reactive gelation is performed by injecting a controlled amount of salt solution into the latex NPs phase to destabilize the suspension and initiate aggregation. As an important highlight of this work, the authors demonstrate the ability of NPs to self-migrate toward the water/oil interface without the addition of salt, due to the electronic attraction of the protonated surfactant used to stabilize the droplets. This is then followed by the gelation as the NPs become close enough to aggregate. Droplets of latex NPs suspension are generated using the well-established segmented-flow microfluidic technology, which enables easy tuning of the diameter from 20 to 100 μm. The precursor droplets geometry thus serves as a template for the final morphology of the microcapsule. After post-polymerization, a solid and porous shell is obtained.

This work can find significant application in the field of microencapsulation and triggered release of payload by providing a direct, unprecedented control over the capsules morphology and permeability.

Written by Julie Probst.

Read the full paper here.

Micro-sized capsules of varying porosity can be obtained by changing the latex NP concentration

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