Talk by A. Callegari at LAOP, Lima, 14 Nov 18

Active Matter Alters the Growth Dynamics of Coffee Rings
Agnese Callegari, Tugba Andaç, Pascal Weigmann, Sabareesh K. Velu, Erçag Pince, Giorgio Volpe & Giovanni Volpe
LAOP – Latin America Optics & Photonics Congress, Lima, Peru
12-15 November 2018

Abstract: We show that bacterial mobility starts playing a major role in determining the growth dynamics of the edge of drying droplets, as the droplet evaporation rate slows down.

Tutorial by G. Volpe and A. Callegari on Optical Tweezers at LAOP, Lima, 12 Nov 18

Optical Trapping and Optical Manipulation
Giovanni Volpe & Agnese Callegari
Tutorial at LAOP – Latin America Optics & Photonics Congress, Lima, Peru
12-15 November 2018

Description: This course will review the theoretical underpinnings of optical trapping and optical manipulation; a review of recent applications; and provide a hands-on tutorial on the use of computational methods to simulate optical trapping and the motion of optically trapped particles.

Time: 09:00 – 13:00
Location: INICTEL-UNI, Lima, Peru

Linkhttps://www.osa.org/en-us/meetings/topical_meetings/osa_latin_america_optics_photonics_conference/program/short_courses_and_tutorials_on_monday_12_november/

Clustering of Janus Particles preprint on ArXiv

Clustering of Janus particles in optical potential driven by hydrodynamic fluxes

Clustering of Janus Particles in Optical Potential Driven by Hydrodynamic Fluxes
S. Masoumeh Mousavi, Sabareesh K. P. Velu, Agnese Callegari, Luca Biancofiore & Giovanni Volpe
arXiv: 1811.01989

Self-organisation is driven by the interactions between the individual components of a system mediated by the environment, and is one of the most important strategies used by many biological systems to develop complex and functional structures. Furthermore, biologically-inspired self-organisation offers opportunities to develop the next generation of materials and devices for electronics, photonics and nanotechnology. In this work, we demonstrate experimentally that a system of Janus particles (silica microspheres half-coated with gold) aggregates into clusters in the presence of a Gaussian optical potential and disaggregates when the optical potential is switched off. We show that the underlying mechanism is the existence of a hydrodynamic flow induced by a temperature gradient generated by the light absorption at the metallic patches on the Janus particles. We also perform simulations, which agree well with the experiments and whose results permit us to clarify the underlying mechanism. The possibility of hydrodynamic-flux-induced reversible clustering may have applications in the fields of drug delivery, cargo transport, bioremediation and biopatterning.

Controlling Colloidal Dynamics by Critical Casimir Forces preprint in arXiv

Controlling the dynamics of colloidal particles by critical Casimir forces

Controlling the dynamics of colloidal particles by critical Casimir forces
Alessandro Magazzù, Agnese Callegari, Juan Pablo Staforelli, Andrea Gambassi, Siegfried Dietrich & Giovanni Volpe
arXiv: 1806.11403

We measure the time evolution of the distance between the two colloids to determine their relative diffusion and drift velocity. Furthermore, we show how critical Casimir forces change the dynamic properties of this two-colloid system by studying the temperature dependence of the distribution of the so-called first-passage time, i.e., of the time necessary for the particles to reach for the first time a certain separation, starting from an initially assigned one. These data are in good agreement with theoretical results obtained from Monte Carlo simulations and Langevin dynamics.

Active Matter Influence on Coffee Rings preprint in arXiv

Active Matter Alters the Growth Dynamics of Coffee Rings

Active Matter Alters the Growth Dynamics of Coffee Rings
Tuğba Andaç, Pascal Weigmann, Sabareesh K. P. Velu, Erçağ Pinçe, Agnese Callegari, Giorgio Volpe & Giovanni Volpe
arXiv: 1803.02619

We experimentally demonstrate the light-controlled assembly of active colloidal molecules from a suspension of two species of passive microspheres.When light is shone on the sample, the active molecules form and acquire motility through non-reciprocal interactions between their passive components. As their size grows, they feature a complex array of behaviors, becoming propellers, spinners and rotators. Their shape and functionality can be tuned by applying periodic illumination. We also provide a theoretical model allowing to predict the complete table of emerging active molecules and their properties in quantitative agreement with the experiments.

Microscopic Critical Engine featured in Phys.Org

Microscopic engine powered by critical demixing

Our recent article Microscopic engine powered by critical remixing
by Falko Schmidt, Alessandro Magazzù, Agnese Callegari, Luca Biancofiore, Frank Cichos & Giovanni Volpe, published in Physical Review Letters 120(6), 068004 (2018) has been featured in “Tiny engine powered by demixing fluid” Phys.Org (February 12, 2018)

Microscopic Critical Engine featured in Optics & Photonics News

Microscopic engine powered by critical demixing

Our recent article Microscopic engine powered by critical remixing
by Falko Schmidt, Alessandro Magazzù, Agnese Callegari, Luca Biancofiore, Frank Cichos & Giovanni Volpe, published in Physical Review Letters 120(6), 068004 (2018) has been featured in “Laser + Critical Liquid = Micro-Engine”, Optics & Photonics News (February 12, 2018)

Optics & Photonics News (OPN) is The Optical Society’s monthly news magazine. It provides in-depth coverage of recent developments in the field of optics and offers busy professionals the tools they need to succeed in the optics industry, as well as informative pieces on a variety of topics such as science and society, education, technology and business. OPN strives to make the various facets of this diverse field accessible to researchers, engineers, businesspeople and students. Contributors include scientists and journalists who specialize in the field of optics.

Microscopic Critical Engine featured in APS Physics

Microscopic engine powered by critical demixing

Our recent article Microscopic engine powered by critical remixing
by Falko Schmidt, Alessandro Magazzù, Agnese Callegari, Luca Biancofiore, Frank Cichos & Giovanni Volpe, published in Physical Review Letters 120(6), 068004 (2018) has been featured in “Focus: A Tiny Engine Powered by Light and Liquid Physics”, Physics 11, 16 (February 9, 2018)

Physics provides daily online-only news and commentary about a selection of papers from the APS journals collection. It is aimed at the reader who wants to keep up with highlights of physics research with explanations that don’t rely on complex technical detail.

The category Physics: focus stories features only a few number of articles each week selected among the set of articles published on all the APS journals.
Research articles that have an interdisciplinary character are usually selected, and their explanations are geared toward students and non-experts. Features are written by a journalist for an audience with a general interest in physics.

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)