'Sweeping rods': the sideways self-propulsion of micro-rods

This project aims to replicate and understand self-propelling mechanisms shown by anisotropic microorganisms that must, on a microscale, overcome viscous drag and Brownian motion. To investigate and understand these systems, we seek to replicate such a self-propulsion with synthetic micron-sized anisotropic particles focusing on the side-ways motion of rod-like particles. For this we propose a simple, yet robust method for producing them in sufficient quantities with proper control over their physical and chemical properties. Aligned polymeric micro- and nano-fibers produced using electrospinning will be sputter-coated with two different metals on both the front and back side, thus creating a ‘Janus’ (two faced) fiber. These fibers are subsequently shortened to rods with desired length and aspect ratio using microtome cutting. The bi-metallic rods will self-propel perpendicular to their long axis when placed in a suitable reactant solution, caused by different catalytic reactions on the two metal surfaces of the rods. Experimental investigations of 2D selfpropulsion on a surface as well as 3D self-propulsion (achieved by density matching the particles and the medium) will be done with optical, fluorescence and fast confocal microscopy. The observations will be used to construct a model of self-propulsion with the possibility to subsequently tune particle geometry and surface chemistry to build more efficient self-propelling systems.