(611e) Engine-Payload Self-Propelling Particles for Efficient Disruption and Cleanup of Oil Films On Water

Velev, O. D., North Carolina State University
Sharma, R., North Carolina State University
D'Costa, L., North Carolina State University

A self-propelling particle uses energy (such as chemical, thermal or electrical) for propulsion by generating local gradients of chemical or other potential. We will first present a class of gel based self-propelling particles moving in a programmed oscillatory mode at water/air interfaces propelled by Marangoni effect. These gel boats floating on the water surface are driven by a hydrogel reservoir releasing an ethanol flux that is periodically disrupted by the bulk flows around the particles. The pulse interval and the distance propelled in a pulse by these gel floaters were interpreted based on the rate of ethanol mass-transfer. The model allowed us to design particles that perform “dances” of repeatable periodic sequences of forward/backward, or rotary steps, and travel in complex pre-programmed trajectories on the liquid surface (Langmuir 28, 10128, 2012). We will then report how on this basis we designed and tested new types of functionalized self-propelling floaters driven by surfactant release that may serve as a new platform for environmental remediation. Previous research on oil collection deals mostly with the synthesis of new immobile adsorbent materials. We demonstrated that self-propelling adsorbent particles can achieve highly efficient oil recovery by rapidly moving over the water surface. The “engine-payload” particles act as motile collectors that can function with a broad range of adsorbent materials. In addition, the Marangoni propulsion leads to oil film disruption, which depends on the type and solubility of the surfactant. In more general plan, this technique offers a radical departure from the present practice of engineering processes where particles adsorb and process a certain component passively, by diffusion of the component towards the stationary (or carried with the fluid) particles. The use of self-propelling adsorbing, catalytic and other particles may allow redefining and drastically intensifying the mass-transport processes in fluid-particle systems.