In this work it is demonstrated that the manipulation of the mesoscale-sized particles through Marangoni flows occurs during the transient regime of the convection cell evolution. By exploiting this fact, it was possible to selectively separate a single glass bead out of a group of other beads ranging from 150 to 212 μm. This task was accomplished by controlling the Marangoni convection cell growth. The growth was controlled by varying the pulse width of an infrared laser beam that acts as a thermal source. Thus, extending the use of the Marangoni flows for single particles sorting or manipulation.
Laser-induced thermocapillary convection flows is a promising technique to manipulate micrometer size particles. Several parameters, such as the laser exposure time, the laser-particle distance, the particles' diameter and the water layer thickness can be used to control the particles' speed. This article deals with the study of the influence of the control parameters in the manipula-* These authors contributed equally to this work.
This paper aims to improve magnetic helical swimming varying the cross-section geometry and considering a conical geometry for helical robot. Both parameters have not been extensively studied in the literature. The conical helix is generated when the helix radial pitch varies constantly and due to that, it could be used in delivery tasks of big-sized millimetric objects. To conceive the whole study, experimentation, and finite-element-method (FEM) simulations are performed in order to corroborate the experimental data in the literature. The influence on the propulsion of the helix cross-section geometry in a cylindrical helix, and the number of turns in a conical helix was demonstrated. Results show that helices with triangular cross-sections provide better propulsion than circular ones, these latter widely used in various micro-and nanoswimmer designs in literature. This result could change the way that helical swimmers are manufactured today. Besides, conical helices with 1-turn and 1.5-turn have shown better performances than multi-turn ones in terms of speed and propulsion force. From this part of the study, the main contribution has been the novel design proposed for delivery tasks.
In this paper, we introduce a novel miniature swimmer with multiple rigid tails. The tails' geometry is based on spherical helices that benefit the swimmers for transporting objects with their flagellar bundle. When the swimmer is rotated, their tails provide a considerable propulsive force to generate a net displacement. Thus, achieving propulsion speeds up to 6 mm/s at 3.5 Hz (small rotation frequencies) for a 6-mm in size prototypes. We study the efficiency of different bundle distribution for a 2-flagella swimmer by varying the phase angle between tails. Moreover, it is demonstrated that these swimmers experience a great sensibility when changing their tail height. Besides, the swimmers demonstrate to be effective for cargo carrying tasks since they can displace objects up to 3.5 times their weight. Finally, the confinement effect is studied with multi-tailed swimmer robots considering 2 containers with 20 and 50-mm in width. Results showed speeds' increments up to 59% when swimmers are actuated in the smaller container.
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