Browsing by Author "Gambassi, A."
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Item Unknown Controlling the dynamics of colloidal particles by critical Casimir forces(Royal Society of Chemistry, 2019-01) Magazzu, A.; Callegari, Agnese; Staforelli, J. P.; Gambassi, A.; Dietrich, S.; Volpe, GiovanniCritical Casimir forces can play an important role for applications in nano-science and nano-technology, owing to their piconewton strength, nanometric action range, fine tunability as a function of temperature, and exquisite dependence on the surface properties of the involved objects. Here, we investigate the effects of critical Casimir forces on the free dynamics of a pair of colloidal particles dispersed in the bulk of a near-critical binary liquid solvent, using blinking optical tweezers. In particular, 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.Item Open Access Erratum: controlling the dynamics of colloidal particles by critical Casimir forces (Soft Matter (2019) 15 (2152-2162) DOI: 10.1039/C8SM01376D)(Royal Society of Chemistry, 2020) Magazzu, A.; Callegari, Agnese; Staforelli, J. P.; Gambassi, A.; Dietrich, S.; Volpe, GiovanniCorrection for ‘Controlling the dynamics of colloidal particles by critical Casimir forces’ by Alessandro Magazzù et al., Soft Matter, 2019, 15, 2152–2162, DOI: 10.1039/C8SM01376D. The authors regret an error in the grant number for one of the authors in the Acknowledgements section. The Acknowledgements section should read as follows: This work was partially supported by the ERC Starting Grant ComplexSwimmers (grant no. 677511) and by Vetenskapsrådet (grant no. 2016-03523). A. C. acknowledges partial financial support from TUBITAK (grant no. 116F111). J. P. S. acknowledges partial financial support from FONDECYT (grant no. 1171013). The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.Item Unknown Experimental investigation of critical Casimir forces in binary liquid mixtures by blinking optical tweezers(OSA, 2017) Magazzu, Alessandro; Schmidt, F.; Callegari, Agnese; Gambassi, A.; Dietrich, S.; Volpe, GiovanniWe investigate, for the first time and by blinking optical tweezers, the effects of critical Casimir forces (CCFs) on the free dynamics of a pair of spherical colloidal particles, immersed in binary liquid mixtures upon approaching their critical points.Item Open Access Nonadditivity of critical Casimir forces(Nature Publishing Group, 2016) Paladugu, S.; Callegari, A.; Tuna Y.; Barth, L.; Dietrich, S.; Gambassi, A.; Volpe, G.In soft condensed matter physics, effective interactions often emerge due to the spatial confinement of fluctuating fields. For instance, microscopic particles dissolved in a binary liquid mixture are subject to critical Casimir forces whenever their surfaces confine the thermal fluctuations of the order parameter of the solvent close to its critical demixing point. These forces are theoretically predicted to be nonadditive on the scale set by the bulk correlation length of the fluctuations. Here we provide direct experimental evidence of this fact by reporting the measurement of the associated many-body forces. We consider three colloidal particles in optical traps and observe that the critical Casimir force exerted on one of them by the other two differs from the sum of the forces they exert separately. This three-body effect depends sensitively on the distance from the critical point and on the chemical functionalisation of the colloid surfaces.Item Open Access Nonadditivity of critical Casimir forces(OSA, 2017) Callegari, Agnese; Paladugu, Sathyanarayana; Tuna, Yazgan; Barth, Lukas; Dietrich, S.; Gambassi, A.; Volpe, GiovanniWe provide the first experimental evidence of nonadditivity for critical Casimir forces: the force that two colloidal particles exert together on a third one differs from the sum of the forces they exert separately.