“Suction Caps”: Designing Anisotropic Core/Shell Microcapsules with Controlled Membrane Mechanics and Substrate Affinity

Abstract

Core/shell microcapsules with low‐permeability membranes and controlled morphology are crucial for the delivery and controlled release of fragrance molecules, pharmaceuticals, inks, or vitamins. Design criteria for next generation microcapsules must include chemical and mechanical stability, and also provide enhanced substrate interactions to improve deposition onto relevant complex surfaces. Here, a coupled approach is presented to synthesize core/shell delivery systems by interfacial polymerization to enhance both the microcapsule–substrate interactions and the mechanical properties of the capsules to induce a burst‐type release. By combining membrane synthesis, nonlinear mechanics, interfacial rheology, analysis of mass transfer, and capsule morphology generated during interfacial polymerization, large permanent deformations into the capsule geometry are programmed, resulting in chemically stable, yet mechanically rupturing microcapsules with anisotropic geometry. To promote interactions and capsule adhesion onto complex substrates, the capsule contact area is controlled to form prominent “suction cup” shaped rims. These capsules have favorable, far‐reaching electrostatic interactions with oppositely charged substrates such as glass, hair, skin, or fabric. By modulating membrane mechanical properties and morphology during synthesis, formulation‐independent physical criteria are used to improve the overall performance of a functional delivery system while expanding knowledge of the key parameters influencing the interfacial polymerization process and membrane formation.

Shape Dependent Colloidal Deposition and Detachment

“…The ability to synthesize a variety of colloidal particle shapes on the micro-and nanoscale has existed for many years [1] and has continued to significantly expand in recent years, [2,3] which has enabled the use of different shaped colloids in diverse technological areas. For example, it is known that colloid shape can enhance drug circulation [4] and cell internalization, [5] fragrance capsule deposition in consumer products, [6,7] hydrodynamic separation processes, [8] environmental transport, [9,10] and specificity in natural systems such as pollen. [11] Beyond this representative list of illustrative examples, a vast literature too expansive to summarize here documents a rich and complex landscape of novel The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adts.201900085 DOI: 10.1002/adts.201900085 behaviors and properties of nonspherical colloids.…”

“…[13] Such core-shell capsules have been shown to buckle into nonspherical shapes, which has been shown to produce enhanced deposition on hair compared to spherical capsules. [6] To exploit and optimize this shape effect, it is essential to understand how nonspherical capsules and their surface chemistry mediate deposition.…”

“…d) Confocal laser scanning microscope (CLSM) and e) scanning electron microscope (SEM) images of bucked anisotropic colloids. [6] Kramer's problem [17] ) has been adapted to model the detachment rate of spherical colloids from planar substrates [18] based on standard potentials such as Derjaguin-Landau-Verwey-Overbeek (DLVO) electrostatic and van der Waals interactions. [19] Such approaches have not been generalized for arbitrary particle-wall interaction potentials, or position and orientation dependent energy landscapes associated with different particle shapes.…”

“…Composite chimeric particles, as the fusion of a hemi-sphere and hemi-toroid, are investigated to model the deposition behavior of buckled fragrance capsules ( Figure 1). [6] Such particles are scientifically interesting as a model of a more complex particle shapes with additional asymmetries that illustrate additional features (without comprehensively exploring more diverse shapes), and are technologically important in consumer products. The Smoluchowski equation is numerically solved to capture particle dynamics based on Brownian motion on 2D energy landscapes (i.e., position and orientation), based on our prior modeling work of anisotropic particle-wall interactions.…”

Nanoparticle Probes for Quantifying Supramolecular Determinants of Biosurface Affinity

“…[8] Most understanding regarding interactions of synthetic and bio-system with biosurfaces is on the charge of each components, such as electrostatic forces between two opposing charged systems. [9,10] The supramolecularly competitive aqueous environment in which these surfaces function makes multivalent interactions a prerequisite.…”