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Fiber-optic rotation of microscopic object. (a) Principle of fiber optic spanner. Fscatt: Scattering force; Fgrad: Gradient force. (b) Schematic of the experimental set up. HAL: halogen lamp; MO: microscope objective; DL: Diode laser; FL: Focusing lens; and SMF 1&2: Single mode fibers.
Microfluidic actuation by fiber-optic spanner. (a) and (b) Time-lapse images of movement of tracer particle (due to microfluidic flow) actuated by fiber-optically rotated microsphere assembly. (c) Angular displacement of the tracer particles as a function of time during assembly rotation (See Movie1, Fig. 4).
Numerical simulation of torque generated by fiber-optic spanner. (a) Ray-optics diagram showing interactions considered in development of the model simulating the torque generated by individual fiber-optic laser beam on the microsphere (radius: R) located at (D, H). D is half of the axial separation between the two fibers. The transverse offset of each counter-propagating beam is h (and that of each microsphere is H) from the center of the two optical axes of the fibers. The incident, reflected, and refracted rays are noted as i, r, and t, respectively. Other high order reflections and refractions are neglected. (b) Numerical simulation of angular velocity of the microsphere-assembly as a function of laser power for different transverse offsets (h).
Two-photon scanning by fiber-optic spanner. (a) Schematic illustrating the focusing of light by rotating spheres for two-photon excitation. (b) Micro-motor consisting of assembly of seven fluorescent spheres. Arrow indicates two-photon excited fluorescence of one sphere. (c) and (d) Time-lapse images of two-photon scanning of microsphere-assembly, actuated by fiber-optical spanner. (e) Mean fluorescence intensity of individual peripheral spheres. Error bars indicate standard deviation around mean (enhanced online). Movie 1. [URL: http://dx.doi.org/10.1063/1.4768232.1]10.1063/1.4768232.1
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