Designing active microcapsules for particle capture*

The large topological changes of microgels, observed through the volume-phase transition, gives these gels the unique ability to induce transport, and force solvent in and out of the constituent polymer network. In our work we use dissipative particle dynamics to study how these materials can be exploited to create a novel microdevice for particle capture. By embedding a spherical microgel in a perforated capsule we leverage these shape changes to selectively capture nanoparticles from particle-rich solvent. Upon application of an external stimulus the gel swells, expanding through the perforated holes and contacting the external solvent. Removal of the external stimulus collapses the microgel into the shell interior, bringing in particles from the external solution. The area around each of the perforations is functionalized with a polymer brush which is used to achieve chemical gating, when the gel is in the collapsed state. We study how the capture rate depends on the swelling period and gel-nanoparticle interactions and we quantify the optimal swelling period which maximizes capture rates.