BilkentResearchers’ Study on Critical Casimir Forces Published in Nature Communications
- 11 August 2016
- Posted by: admin
- Category: News
A team of researchersled by Asst. Prof. Giovanni Volpe (Soft MatterLab, Department of Physics and UNAM) has published an important study in the open-access journal Nature Communications (April 21, 2016). In the study, coauthored by Prof. Andrea Gambassi of the International School for Advanced Study (SISSA) in Trieste, Italy, the investigatorsmeasured the presence of many-body effects for critical Casimir forces, i.e., forces acting on microscopicparticlesimmersed in a fluidinduced by critical fluctuations.
The term “many-body effects” refers to the factthat the effecttwomicroparticles have on a third one togethermight not be the same as the sum of the effectstheywould have separately. Just as in the macroscopic world, the sum of the parts in the microscopic world isoftendifferentfrom the whole, and interactions canbequitecomplex.
In the studyjustpublished, researchers for the first time measuredthiseffect in a system formed by glass colloidsimmersed in a critical mixture. By reconstructing the critical Casimir forces when the system wasformed by two and then by threecolloids, the physicistsdemonstrated the nonadditivity of these forces. “The knowledge of theseeffectsisvery important from the point of view of bothfundamental and appliedresearch, especially for the scientistswho design micro-machines able to do a variety of tasks,” notes Prof. Gambassi.
In the experimentconducted by Dr. Volpe’s group, the particleswereimmersed in a mixture of water and lutidine, and twoparticlesconfined in place via opticaltweezerssuchthat a film of theirrandom motion couldbe made through the microscope and, via statisticalmethods, the forces atplayaccuratelyinferred. The researchersthenadded a thirdparticle and compared the results. “In thisway,” declared Dr. Volpe, “wedemonstratedthat the many-body effectis real, and wesucceeded in measuringitwith an unexpectedaccuracy: after all, weweredealingwith forces that are a thousandth of a millionth of a gram.”
In addition to Dr. Volpe and Prof. Gambassi, the research team included Dr. SathyanarayanaPaladugu, Dr. AgneseCallegari and Lukas Barth of the Soft MatterLabatBilkent; YazganTuna of the Soft MatterLab and UNAM atBilkent; and Prof. Siegfried Dietrich of the Max-Planck-Institute for Intelligent Systems and the IV. Institute for TheoreticalPhysicsat the University of Stuttgart.