Browsing by Author "Schmidt, F."

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    A critical microscopic engine in an optical tweezers
    (OSA, 2018) Schmidt, F.; Magazzù, Agnese; Callegari, A.; Biancofiore, Luca; Cichos, F.; Volpe, G.
    An optically trapped absorbing microsphere in a sub-critical mixture rotates around the optical trap thanks to diffusiophoretic propulsion, which can be controlled by adjusting the optical power, the temperature, and the criticality of the mixture.
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    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, Giovanni
    We 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.
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    Microscopic engine powered by critical demixing
    (American Physical Society, 2018) Schmidt, F.; Magazzù, A.; Callegari, Agnese; Biancofiore, Luca; Cichos, F.; Volpe, G.
    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 subcritical 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.
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    Microscopic engine powered by critical demixing
    (OSA, 2017) Schmidt, F.; Magazzu, Alessandro; Callegari, Agnese; Biancofiore, Luca; Cichos, F.; Volpe, Giovanni
    We propose a new type of engine that is powered by the local, reversible demixing of a critical binary liquid. A microscopic particle is optically trapped and performs revolutions due to the emergence of diffusiophoresis.
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    Optically driven janus microengine with full orbital motion control
    (American Chemical Society, 2023-09-20) Bronte Ciriza, D.; Callegari, A.; Donato, M. G.; Çiçek, Berk; Magazzù, A.; Kasianiuk, Iryna; Kasyanyuk, Denis; Schmidt, F.; Foti, A.; Gucciardi, P. G.; Volpe, G.; Lanza, M.; Biancofiore, Luca; Maragò, O. M.
    Microengines have shown promise for a variety of applications in nanotechnology, microfluidics, and nanomedicine, including targeted drug delivery, microscale pumping, and environmental remediation. However, achieving precise control over their dynamics remains a significant challenge. In this study, we introduce a microengine that exploits both optical and thermal effects to achieve a high degree of controllability. We find that in the presence of a strongly focused light beam, a gold-silica Janus particle becomes confined at the stationary point where the optical and thermal forces balance. By using circularly polarized light, we can transfer angular momentum to the particle, breaking the symmetry between the two forces and resulting in a tangential force that drives directed orbital motion. We can simultaneously control the velocity and direction of rotation of the particle changing the ellipticity of the incoming light beam while tuning the radius of the orbit with laser power. Our experimental results are validated using a geometrical optics phenomenological model that considers the optical force, the absorption of optical power, and the resulting heating of the particle. The demonstrated enhanced flexibility in the control of microengines opens up new possibilities for their utilization in a wide range of applications, including microscale transport, sensing, and actuation.