Speaker
Description
Ion-exchange polymers offer a versatile platform for self-phoretic active colloids. Nafion, rich in sulfonic groups, generates strong ionic gradients and electric fields during counterion exchange when immersed in water, enabling autonomous fluid pumping and propulsion. Building on our earlier work with immobilized Nafion pumps, we now extend these concepts to fully motile colloidal swimmers. We fabricate asymmetric Nafion, metal hybrid micro- and nanoswimmers, typically Nafion rods capped with metals and metal oxides, using colloidal and stencil lithographic methods. In aqueous electrolytes, these structures display robust self-phoretic motion driven solely by ion exchange. Beyond individual propulsion, they exhibit diverse collective behaviours, including clustering, swarming, cooperative translation, and mobile pumping that draws in and concentrates surrounding material. We further show that wall zeta potential influences propulsion orientation, and collective patterns. Overall, Nafion-based ion-exchange micromachines provide a tunable polymeric model for studying self-phoretic propulsion, active-matter interactions, and emergent collective dynamics, with potential applications in pollutant capture and adaptive micro-/nanosystems.
