Measurement of the optical trapping force on micro-particles immersed in fluids

Nadasan, Monica, Kulkarni, Revati, Ferrari, Enrico , Garbin, Valeria, Cojoc, Dan and Di Fabrizio, Enzo (2004) Measurement of the optical trapping force on micro-particles immersed in fluids. In: Advanced Topics in Optoelectronics, Microelectronics, and Nanotechnologies II, 24-26 November 2004, Bucharest, Romania.

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Item Type:Conference or Workshop contribution (Paper)
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A strongly focused laser beam through an objective microscope with high NA allows the trapping of dielectric particleswith micrometric sizes. The trapping force is proportional to the power of the laser, the relative refractive index (the ratiobetween the refractive index of the particle and the refractive index of the medium surrounding it) and the trappinggeometry (shape of the laser beam, shape of the particle, transmission and reflection coefficients). Numerical models toevaluate the trapping force can be developed for simple geometrical shapes of the trapped particle. For particles withcomplicated shapes the trapping force should be measured experimentally. The goal of this paper is to evaluate ameasurement method based on the equilibrium between the drag force in a fluid with known viscosity and the transversaltrapping force. A particle with a known size is fist trapped in a cell filled with water. After stable trapping, the cell isshifted with controlled velocities using piezoelectric actuators. If the velocity exceeds a certain threshold, the particleescapes from the trap. This threshold allows to determine the trapping force. Experimental results obtained with high andlow index particles are presented and discussed.

Additional Information:Advanced Topics in Optoelectronics, Microelectronics and Nanotechnologies II, 24-26 November 2004, Bucharest (Romania)
Keywords:optical trapping
Subjects:F Physical Sciences > F310 Applied Physics
Divisions:College of Science > School of Life Sciences
ID Code:8407
Deposited On:26 Mar 2013 17:25

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