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September 19, 2014 at 6:30 pm

Physics Colloquium: Active Brownian Motion, Sept. 19

Fabio Marchesoni

Fabio Marchesoni

The Physics & Astronomy Colloquium Series presents Fabio Marchesoni of the University of Camerino  “Active Brownian Motion” on Friday, Sept. 19, at 4:10 p.m. in Walter 245.

Abstract: Self-propulsion is the ability of most living organisms to move in the absence of external drives, thanks to an “engine” of their own. Realizing and optimizing self-propulsion of micro- and nano-particles (artificial microswimmers) is a fast growing topic of today’s nanotechnology. Recently, a new type of artificial microswimmers has been synthesized, where self-propulsion takes advantage of the local gradients asymmetric particles generate in the presence of an external energy source (self-phoretic effects). Such particles, a.k.a. Janus particles, consist of two distinct “faces,” only one of which is chemically or physically active. Janus particles can thus induce either concentration gradients (self-diffusiophoresis) by catalyzing a chemical reaction on their active surface, or thermal gradients (self-thermophoresis), by inhomogeneous light or magnetic excitation.

I discuss the diffusion of self-propelled Janus particles both in the bulk and in confined geometries. In the bulk they undergo a distinct kind of Brownian motion (active Brownian motion) with diffusion constant that strongly depends on the self-propulsion mechanism. Moreover, since active Brownian motion is time correlated per se, Janus particles can be easily rectified along channels of appropriate geometries (autonomous ratchet). The ultimate goal of this line of research is to explore the possibility of employing active Brownian particles as intelligent micro- or nano-robots, eg., for biomedical applications.

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