Browsing by Author "Chang, YR"

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Optical trapping of a spherically symmetric Rayleigh sphere: a model for optical tweezers upon cells
(2005-02-01)
Chang, YR
;
Hsu, L
;
Chi, S
;
電子物理學系
;
光電工程學系
Optical tweezers have become a popular manipulation and force measurement tool in cellular and molecular biology. However, there is still a lack of a sophisticated model for optical tweezers on trapping cells. In this paper, we present a novel model for optical tweezers to calculate the stiffness of trapping force upon a spherically symmetric Rayleigh sphere, which stimulates a common biological cell. A numerical simulation of this model shows that the stiffness of an optical tweezers system in trapping a cell is significantly smaller than that in trapping a polystyrene bead of the same size. Furthermore, under a small variant condition of the refractive index, the proposed model provides an approximate method which requires only the radial distribution of the trapped cell's refractive index for calculating the stiffness. (C) 2004 Elsevier B.V. All rights reserved.
Optical trapping of a spherically symmetric sphere in the ray-optics regime: a model for optical tweezers upon cells
(2006-06-01)
Chang, YR
;
Hsu, L
;
Chi, S
;
電子物理學系
;
光電工程學系
Since their invention in 1986, optical tweezers have become a popular manipulation and force measurement tool in cellular and molecular biology. However, until recently there has not been a sophisticated model for optical tweezers on trapping cells in the ray-optics regime. We present a model for optical tweezers to calculate the optical force upon a spherically symmetric multilayer sphere representing a common biological cell. A numerical simulation of this model shows that not only is the magnitude of the optical force upon a Chinese hamster ovary cell significantly three times smaller than that upon a polystyrene bead of the same size, but the distribution of the optical force upon a cell is also much different from that upon a uniform particle, and there is a 30% difference in the optical trapping stiffness of these two cases. Furthermore, under a small variant condition for the refractive indices of any adjacent layers of the sphere, this model provides a simple approximation to calculate the optical force and the stiffness of an optical tweezers system. (c) 2006 Optical Society of America.