Customized and durable encapsulation through electrostatic interactions

Customized and durable encapsulation through electrostatic interactions

Mon, 11/07/2022


Publication of the LPENSL in the journal Physical Review Applied on July 6, 2022. CNRS-INP communication on July 7, 2022.

We propose an original microbubble encapsulation process, using electrostatics as a driving force to guide either particles or polymerizable precursors to the bubble surface. Taking advantage of attractive interactions between surfactant-laden charged bubbles and oppositely charged self-assembling species, our method produces capsules with diverse protective shells that remain stable for years. Considering heterogeneous electrostatic double-layer interactions, we quantitatively predict critical particle surface potentials required for complete encapsulation. The particle-based shells can be disintegrated with a pH adjustment, allowing for a controlled release of encapsulated payloads, while the glassy continuous silicate capsules are chemically resistant to pH changes. Our process, which can be equally applied to liquid droplets, easily scales up for industrial developments.

Scheme of the bubble surrounded by a layer of positively charged surfactant. The green strands represent the hydrophobic chains. By adjusting the pH and adding particles (e.g. glass beads) or silicate ions to the solution, the bubble will be surrounded by a row of self-assembled particles or a silicate gel (in grey). In the case of the gel, the shell formed is chemically resistant and the encapsulation is irreversible.


Scanning Electron Microscopy image of an open glass bead capsule showing the assembly of nanometric glass beads. The experiment takes place at low temperature (cryomicroscopy) in order not to destroy the capsule with the electron beam.


Reference: Microbubble Encapsulation by Electrostatic Templating with Ionic Surfactants. Vance Bergeron, Ramon Planet, and Stéphane Santucci Phys. Rev. Applied, July 6, 2022.

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