EAGER: Propulsion of enzyme-coated Janus particles through complex environments

Rensselaer Polytechnic Institute, Troy NY

Investigators

Abstract

CBET - 1544617 PI: Underhill, Patrick The goals of this project are to synthesize a micron-sized particle that is capable of self-propulsion and to characterize the motion of the particle in complex fluids. A portion of the surface of the spherical particle is coated with an enzyme that reacts with peroxide in the surrounding fluid. The reaction at the particle surface creates an osmotic pressure difference across the particle, which causes it to move. The enzymatic reaction can propel the particle at very low peroxide concentrations in the surrounding media, which makes the self-propelled particle a candidate for use in biological systems that are sensitive to peroxide concentration. The velocity of the particle will be measured for a series of viscous fluids, including complex fluids that are models of biological media. Self-propelled particles are promising vehicles to enhance transport and deliver molecular cargoes in complex environments ranging from multiphase fluid systems to biological tissues. The researchers will involve undergraduate and high school students in the project and use results of the research in outreach programs at their institution. The project comprises experimental and theoretical studies to quantify and elucidate mechanisms for the self-driven motion of colloidal particles through non-Newtonian environments. The experiments will utilize a class of Janus particles that propel themselves using an enzyme coated on part of their surface. Motion results from the reaction of a peroxide fuel in solution on the particle surface producing a non-uniform distribution of solutes around the particle, which leads to propulsion by a mechanism called self-diffusiophoresis. The project will test predictions of current theories of self-diffusiophoresis in Newtonian fluids, especially the dependence of particle velocity on fluid viscosity, and then examine motion in more complex, non-Newtonian fluids that are homogeneous on the size scale of the propelling particle. This will be done using polymer solutions in which the polymer radius of gyration is significantly smaller than the motor. Results will form a foundation for self-propelled particle design and use in complex and multiphase fluids.