News

Microscopic Critical Engine published in Phys. Rev. Lett.

Microscopic engine powered by critical demixing

Microscopic engine powered by critical demixing
Falko Schmidt, Alessandro Magazzù, Agnese Callegari, Luca Biancofiore, Frank Cichos & Giovanni Volpe
Physical Review Letters 120(6), 068004 (2018)
DOI: 10.1103/PhysRevLett.120.068004
arXiv: 1705.03317

We experimentally demonstrate a microscopic engine powered by the local reversible demixing of a critical mixture. We show that, when an absorbing microsphere is optically trapped by a focused laser beam in a sub-critical mixture, it is set into rotation around the optical axis of the beam because of the emergence of diffusiophoretic propulsion. This behavior can be controlled by adjusting the optical power, the temperature, and the criticality of the mixture.

Featured in :
“Focus: A Tiny Engine Powered by Light and Liquid Physics”, Physics 11, 16 (February 9, 2018)
“Laser + Critical Liquid = Micro-Engine”, Optics & Photonics News (February 12, 2018)
“Tiny engine powered by demixing fluid” Phys.Org (February 12, 2018)
“Расслаивание растворителя закрутило микрочастицы вокруг лазерного пучка”, N+1: научные статьи, новости, открытия (February 12, 2018)
“Tiny engine powered by remixing fluid”, Brinkwire (February 16, 2018)

 

Seminar by G. Volpe at Institute of Protein Biochemistry (CNR), Naples, 25 Jan 2018

Active Matter in Complex and Crowded Environments
Giovanni Volpe
Institute of Protein Biochemistry, National Research Council (CNR), Naples, Italy
25 January 2018

http://www.ibp.cnr.it/news/seminars/thursday-the-25th-prof-giovanni-volpe-active-matter-in-complex-and-crowded-environments

Dynamic Deposition of Particles in Evaporating Droplets published in J. Phys. Chem. Lett.

Dynamic control of particle deposition in evaporating droplets by an external point source vapor

Dynamic control of particle deposition in evaporating droplets by an external point source vapor
Robert Malinowski, Giovanni Volpe, Ivan Parkin & Giorgio Volpe
The Journal of Physical Chemistry Letters 9(3), 659—664 (2018)
DOI: 10.1021/acs.jpclett.7b02831
arXiv: 1801.08218

The deposition of particles on a surface by an evaporating sessile droplet is important for phenomena as diverse as printing, thin-film deposition, and self-assembly. The shape of the final deposit depends on the flows within the droplet during evaporation. These flows are typically determined at the onset of the process by the intrinsic physical, chemical, and geometrical properties of the droplet and its environment. Here, we demonstrate deterministic emergence and real-time control of Marangoni flows within the evaporating droplet by an external point source of vapor. By varying the source location, we can modulate these flows in space and time to pattern colloids on surfaces in a controllable manner.