# Morphological Control of Single-Concave Elastomeric Colloid through Cross-Linking and Osmotic Pressure Variations for Chemical Delivery

## TL;DR

This paper introduces a method to create single-concave PDMS shells that can absorb and release chemicals, useful for drug delivery and sensing.

## Contribution

A novel method for creating buckled PDMS shells using cross-linking and osmotic pressure for controlled chemical delivery.

## Key findings

- Buckled PDMS shells were formed through double-emulsion solvent evaporation and cross-linking stress.
- Morphology of the shells was controlled by varying permeant concentration and molecular weight.
- The shells showed reversible swelling and release of Nile red molecules in solvents like ethanol.

## Abstract

In this paper, we
propose a convenient and simple method for preparing
elastomeric buckled spherical shells through double-emulsion solvent
evaporation. In this method, polydimethylsiloxane (PDMS) is added
to a water-in-oil-in-water emulsion system and stirred. As the solvent
evaporates and the colloid solidifies, the aqueous phase inside formed
cavity is squeezed out because of cross-linking stress, or this phase
permeates the sphere, leading to loss of the internal water phase
and the formation of a single-concave, bowl-shaped shell (i.e., a
shell with buckling deformation). We could control the morphology
of the produced colloidal particles by varying the concentrations
of the permeant and cross-linking agent and the molecular weight of
the permeant. Moreover, we propose a mechanism explaining the structural
changes occurring during the double-emulsion polymerization process,
focusing on cross-linking forces and osmotic pressure. Through leveraging
of the shells’ reversible swelling properties in solvents,
the prepared buckled PDMS shells absorbed Nile red molecules into
their cavity, which caused their expansion and restoration. Immersing
these shells in ethanol resulted in release of the Nile red molecules.
Thus, buckled PDMS shells prepared through the proposed method have
potential for application in environmental sensing and drug delivery
systems.